Package org.apache.commons.lang

## Class StringUtils

- java.lang.Object
- - org.apache.commons.lang.StringUtils

-     public class StringUtils
      extends Object

  Operations on `String` that are `null` safe.

  - IsEmpty/IsBlank - checks if a String contains text
  - Trim/Strip - removes leading and trailing whitespace
  - Equals - compares two strings null-safe
  - startsWith - check if a String starts with a prefix null-safe
  - endsWith - check if a String ends with a suffix null-safe
  - IndexOf/LastIndexOf/Contains - null-safe index-of checks
  - IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut - index-of any of a set of Strings
  - ContainsOnly/ContainsNone/ContainsAny - does String contains only/none/any of these characters
  - Substring/Left/Right/Mid - null-safe substring extractions
  - SubstringBefore/SubstringAfter/SubstringBetween - substring extraction relative to other strings
  - Split/Join - splits a String into an array of substrings and vice versa
  - Remove/Delete - removes part of a String
  - Replace/Overlay - Searches a String and replaces one String with another
  - Chomp/Chop - removes the last part of a String
  - LeftPad/RightPad/Center/Repeat - pads a String
  - UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize - changes the case of a String
  - CountMatches - counts the number of occurrences of one String in another
  - IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable - checks the characters in a String
  - DefaultString - protects against a null input String
  - Reverse/ReverseDelimited - reverses a String
  - Abbreviate - abbreviates a string using ellipsis
  - Difference - compares Strings and reports on their differences
  - LevensteinDistance - the number of changes needed to change one String into another

  The `StringUtils` class defines certain words related to String handling.

  - null - `null`
  - empty - a zero-length string (`""`)
  - space - the space character (`' '`, char 32)
  - whitespace - the characters defined by `Character.isWhitespace(char)`
  - trim - the characters <= 32 as in `String.trim()`

  `StringUtils` handles `null` input Strings quietly. That is to say that a `null` input will return `null`. Where a `boolean` or `int` is being returned details vary by method.

  A side effect of the `null` handling is that a `NullPointerException` should be considered a bug in `StringUtils` (except for deprecated methods).

  Methods in this class give sample code to explain their operation. The symbol `*` is used to indicate any input including `null`.

  #ThreadSafe#

  Since:
    1.0
  Version:
    $Id: StringUtils.java 1058365 2011-01-13 00:04:49Z niallp $
  See Also:
    `String`

- - ### Field Summary

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `static String` | `EMPTY` | The empty String `""`.
    `static int` | `INDEX_NOT_FOUND` | Represents a failed index search.

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `StringUtils()` | `StringUtils` instances should NOT be constructed in standard programming.

  - ### Method Summary

    All Methods Static Methods Concrete Methods Deprecated Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `static String` | `abbreviate​(String str, int maxWidth)` | Abbreviates a String using ellipses.
    `static String` | `abbreviate​(String str, int offset, int maxWidth)` | Abbreviates a String using ellipses.
    `static String` | `abbreviateMiddle​(String str, String middle, int length)` | Abbreviates a String to the length passed, replacing the middle characters with the supplied replacement String.
    `static String` | `capitalise​(String str)` | Deprecated. Use the standardly named `capitalize(String)`.
    `static String` | `capitaliseAllWords​(String str)` | Deprecated. Use the relocated `WordUtils.capitalize(String)`.
    `static String` | `capitalize​(String str)` | Capitalizes a String changing the first letter to title case as per `Character.toTitleCase(char)`.
    `static String` | `center​(String str, int size)` | Centers a String in a larger String of size `size` using the space character (' ').
    `static String` | `center​(String str, int size, char padChar)` | Centers a String in a larger String of size `size`.
    `static String` | `center​(String str, int size, String padStr)` | Centers a String in a larger String of size `size`.
    `static String` | `chomp​(String str)` | Removes one newline from end of a String if it's there, otherwise leave it alone.
    `static String` | `chomp​(String str, String separator)` | Removes `separator` from the end of `str` if it's there, otherwise leave it alone.
    `static String` | `chompLast​(String str)` | Deprecated. Use `chomp(String)` instead.
    `static String` | `chompLast​(String str, String sep)` | Deprecated. Use `chomp(String,String)` instead.
    `static String` | `chop​(String str)` | Remove the last character from a String.
    `static String` | `chopNewline​(String str)` | Deprecated. Use `chomp(String)` instead.
    `static String` | `clean​(String str)` | Deprecated. Use the clearer named `trimToEmpty(String)`.
    `static String` | `concatenate​(Object[] array)` | Deprecated. Use the better named `join(Object[])` instead.
    `static boolean` | `contains​(String str, char searchChar)` | Checks if String contains a search character, handling `null`.
    `static boolean` | `contains​(String str, String searchStr)` | Checks if String contains a search String, handling `null`.
    `static boolean` | `containsAny​(String str, char[] searchChars)` | Checks if the String contains any character in the given set of characters.
    `static boolean` | `containsAny​(String str, String searchChars)` | Checks if the String contains any character in the given set of characters.
    `static boolean` | `containsIgnoreCase​(String str, String searchStr)` | Checks if String contains a search String irrespective of case, handling `null`.
    `static boolean` | `containsNone​(String str, char[] searchChars)` | Checks that the String does not contain certain characters.
    `static boolean` | `containsNone​(String str, String invalidChars)` | Checks that the String does not contain certain characters.
    `static boolean` | `containsOnly​(String str, char[] valid)` | Checks if the String contains only certain characters.
    `static boolean` | `containsOnly​(String str, String validChars)` | Checks if the String contains only certain characters.
    `static int` | `countMatches​(String str, String sub)` | Counts how many times the substring appears in the larger String.
    `static String` | `defaultIfBlank​(String str, String defaultStr)` | Returns either the passed in String, or if the String is whitespace, empty ("") or `null`, the value of `defaultStr`.
    `static String` | `defaultIfEmpty​(String str, String defaultStr)` | Returns either the passed in String, or if the String is empty or `null`, the value of `defaultStr`.
    `static String` | `defaultString​(String str)` | Returns either the passed in String, or if the String is `null`, an empty String ("").
    `static String` | `defaultString​(String str, String defaultStr)` | Returns either the passed in String, or if the String is `null`, the value of `defaultStr`.
    `static String` | `deleteSpaces​(String str)` | Deprecated. Use the better localized `deleteWhitespace(String)`.
    `static String` | `deleteWhitespace​(String str)` | Deletes all whitespaces from a String as defined by `Character.isWhitespace(char)`.
    `static String` | `difference​(String str1, String str2)` | Compares two Strings, and returns the portion where they differ.
    `static boolean` | `endsWith​(String str, String suffix)` | Check if a String ends with a specified suffix.
    `static boolean` | `endsWithAny​(String string, String[] searchStrings)` | Check if a String ends with any of an array of specified strings.
    `static boolean` | `endsWithIgnoreCase​(String str, String suffix)` | Case insensitive check if a String ends with a specified suffix.
    `static boolean` | `equals​(String str1, String str2)` | Compares two Strings, returning `true` if they are equal.
    `static boolean` | `equalsIgnoreCase​(String str1, String str2)` | Compares two Strings, returning `true` if they are equal ignoring the case.
    `static String` | `escape​(String str)` | Deprecated. Use `StringEscapeUtils.escapeJava(String)` This method will be removed in Commons Lang 3.0
    `static String` | `getChomp​(String str, String sep)` | Deprecated. Use `substringAfterLast(String, String)` instead (although this doesn't include the separator) Method will be removed in Commons Lang 3.0.
    `static String` | `getCommonPrefix​(String[] strs)` | Compares all Strings in an array and returns the initial sequence of characters that is common to all of them.
    `static int` | `getLevenshteinDistance​(String s, String t)` | Find the Levenshtein distance between two Strings.
    `static String` | `getNestedString​(String str, String tag)` | Deprecated. Use the better named `substringBetween(String, String)`.
    `static String` | `getNestedString​(String str, String open, String close)` | Deprecated. Use the better named `substringBetween(String, String, String)`.
    `static String` | `getPrechomp​(String str, String sep)` | Deprecated. Use `substringBefore(String,String)` instead (although this doesn't include the separator).
    `static int` | `indexOf​(String str, char searchChar)` | Finds the first index within a String, handling `null`.
    `static int` | `indexOf​(String str, char searchChar, int startPos)` | Finds the first index within a String from a start position, handling `null`.
    `static int` | `indexOf​(String str, String searchStr)` | Finds the first index within a String, handling `null`.
    `static int` | `indexOf​(String str, String searchStr, int startPos)` | Finds the first index within a String, handling `null`.
    `static int` | `indexOfAny​(String str, char[] searchChars)` | Search a String to find the first index of any character in the given set of characters.
    `static int` | `indexOfAny​(String str, String searchChars)` | Search a String to find the first index of any character in the given set of characters.
    `static int` | `indexOfAny​(String str, String[] searchStrs)` | Find the first index of any of a set of potential substrings.
    `static int` | `indexOfAnyBut​(String str, char[] searchChars)` | Search a String to find the first index of any character not in the given set of characters.
    `static int` | `indexOfAnyBut​(String str, String searchChars)` | Search a String to find the first index of any character not in the given set of characters.
    `static int` | `indexOfDifference​(String[] strs)` | Compares all Strings in an array and returns the index at which the Strings begin to differ.
    `static int` | `indexOfDifference​(String str1, String str2)` | Compares two Strings, and returns the index at which the Strings begin to differ.
    `static int` | `indexOfIgnoreCase​(String str, String searchStr)` | Case in-sensitive find of the first index within a String.
    `static int` | `indexOfIgnoreCase​(String str, String searchStr, int startPos)` | Case in-sensitive find of the first index within a String from the specified position.
    `static boolean` | `isAllLowerCase​(String str)` | Checks if the String contains only lowercase characters.
    `static boolean` | `isAllUpperCase​(String str)` | Checks if the String contains only uppercase characters.
    `static boolean` | `isAlpha​(String str)` | Checks if the String contains only unicode letters.
    `static boolean` | `isAlphanumeric​(String str)` | Checks if the String contains only unicode letters or digits.
    `static boolean` | `isAlphanumericSpace​(String str)` | Checks if the String contains only unicode letters, digits or space (`' '`).
    `static boolean` | `isAlphaSpace​(String str)` | Checks if the String contains only unicode letters and space (' ').
    `static boolean` | `isAsciiPrintable​(String str)` | Checks if the string contains only ASCII printable characters.
    `static boolean` | `isBlank​(String str)` | Checks if a String is whitespace, empty ("") or null.
    `static boolean` | `isEmpty​(String str)` | Checks if a String is empty ("") or null.
    `static boolean` | `isNotBlank​(String str)` | Checks if a String is not empty (""), not null and not whitespace only.
    `static boolean` | `isNotEmpty​(String str)` | Checks if a String is not empty ("") and not null.
    `static boolean` | `isNumeric​(String str)` | Checks if the String contains only unicode digits.
    `static boolean` | `isNumericSpace​(String str)` | Checks if the String contains only unicode digits or space (`' '`).
    `static boolean` | `isWhitespace​(String str)` | Checks if the String contains only whitespace.
    `static String` | `join​(Object[] array)` | Joins the elements of the provided array into a single String containing the provided list of elements.
    `static String` | `join​(Object[] array, char separator)` | Joins the elements of the provided array into a single String containing the provided list of elements.
    `static String` | `join​(Object[] array, char separator, int startIndex, int endIndex)` | Joins the elements of the provided array into a single String containing the provided list of elements.
    `static String` | `join​(Object[] array, String separator)` | Joins the elements of the provided array into a single String containing the provided list of elements.
    `static String` | `join​(Object[] array, String separator, int startIndex, int endIndex)` | Joins the elements of the provided array into a single String containing the provided list of elements.
    `static String` | `join​(Collection collection, char separator)` | Joins the elements of the provided `Collection` into a single String containing the provided elements.
    `static String` | `join​(Collection collection, String separator)` | Joins the elements of the provided `Collection` into a single String containing the provided elements.
    `static String` | `join​(Iterator iterator, char separator)` | Joins the elements of the provided `Iterator` into a single String containing the provided elements.
    `static String` | `join​(Iterator iterator, String separator)` | Joins the elements of the provided `Iterator` into a single String containing the provided elements.
    `static int` | `lastIndexOf​(String str, char searchChar)` | Finds the last index within a String, handling `null`.
    `static int` | `lastIndexOf​(String str, char searchChar, int startPos)` | Finds the last index within a String from a start position, handling `null`.
    `static int` | `lastIndexOf​(String str, String searchStr)` | Finds the last index within a String, handling `null`.
    `static int` | `lastIndexOf​(String str, String searchStr, int startPos)` | Finds the first index within a String, handling `null`.
    `static int` | `lastIndexOfAny​(String str, String[] searchStrs)` | Find the latest index of any of a set of potential substrings.
    `static int` | `lastIndexOfIgnoreCase​(String str, String searchStr)` | Case in-sensitive find of the last index within a String.
    `static int` | `lastIndexOfIgnoreCase​(String str, String searchStr, int startPos)` | Case in-sensitive find of the last index within a String from the specified position.
    `static int` | `lastOrdinalIndexOf​(String str, String searchStr, int ordinal)` | Finds the n-th last index within a String, handling `null`.
    `static String` | `left​(String str, int len)` | Gets the leftmost `len` characters of a String.
    `static String` | `leftPad​(String str, int size)` | Left pad a String with spaces (' ').
    `static String` | `leftPad​(String str, int size, char padChar)` | Left pad a String with a specified character.
    `static String` | `leftPad​(String str, int size, String padStr)` | Left pad a String with a specified String.
    `static int` | `length​(String str)` | Gets a String's length or `0` if the String is `null`.
    `static String` | `lowerCase​(String str)` | Converts a String to lower case as per `String.toLowerCase()`.
    `static String` | `lowerCase​(String str, Locale locale)` | Converts a String to lower case as per `String.toLowerCase(Locale)`.
    `static String` | `mid​(String str, int pos, int len)` | Gets `len` characters from the middle of a String.
    `static String` | `normalizeSpace​(String str)` | Similar to http://www.w3.org/TR/xpath/#function-normalize -space
    `static int` | `ordinalIndexOf​(String str, String searchStr, int ordinal)` | Finds the n-th index within a String, handling `null`.
    `static String` | `overlay​(String str, String overlay, int start, int end)` | Overlays part of a String with another String.
    `static String` | `overlayString​(String text, String overlay, int start, int end)` | Deprecated. Use better named `overlay(String, String, int, int)` instead.
    `static String` | `prechomp​(String str, String sep)` | Deprecated. Use `substringAfter(String,String)` instead.
    `static String` | `remove​(String str, char remove)` | Removes all occurrences of a character from within the source string.
    `static String` | `remove​(String str, String remove)` | Removes all occurrences of a substring from within the source string.
    `static String` | `removeEnd​(String str, String remove)` | Removes a substring only if it is at the end of a source string, otherwise returns the source string.
    `static String` | `removeEndIgnoreCase​(String str, String remove)` | Case insensitive removal of a substring if it is at the end of a source string, otherwise returns the source string.
    `static String` | `removeStart​(String str, String remove)` | Removes a substring only if it is at the begining of a source string, otherwise returns the source string.
    `static String` | `removeStartIgnoreCase​(String str, String remove)` | Case insensitive removal of a substring if it is at the begining of a source string, otherwise returns the source string.
    `static String` | `repeat​(String str, int repeat)` | Repeat a String `repeat` times to form a new String.
    `static String` | `repeat​(String str, String separator, int repeat)` | Repeat a String `repeat` times to form a new String, with a String separator injected each time.
    `static String` | `replace​(String text, String searchString, String replacement)` | Replaces all occurrences of a String within another String.
    `static String` | `replace​(String text, String searchString, String replacement, int max)` | Replaces a String with another String inside a larger String, for the first `max` values of the search String.
    `static String` | `replaceChars​(String str, char searchChar, char replaceChar)` | Replaces all occurrences of a character in a String with another.
    `static String` | `replaceChars​(String str, String searchChars, String replaceChars)` | Replaces multiple characters in a String in one go.
    `static String` | `replaceEach​(String text, String[] searchList, String[] replacementList)` | Replaces all occurrences of Strings within another String.
    `static String` | `replaceEachRepeatedly​(String text, String[] searchList, String[] replacementList)` | Replaces all occurrences of Strings within another String.
    `static String` | `replaceOnce​(String text, String searchString, String replacement)` | Replaces a String with another String inside a larger String, once.
    `static String` | `reverse​(String str)` | Reverses a String as per `StrBuilder.reverse()`.
    `static String` | `reverseDelimited​(String str, char separatorChar)` | Reverses a String that is delimited by a specific character.
    `static String` | `reverseDelimitedString​(String str, String separatorChars)` | Deprecated. Use `reverseDelimited(String, char)` instead.
    `static String` | `right​(String str, int len)` | Gets the rightmost `len` characters of a String.
    `static String` | `rightPad​(String str, int size)` | Right pad a String with spaces (' ').
    `static String` | `rightPad​(String str, int size, char padChar)` | Right pad a String with a specified character.
    `static String` | `rightPad​(String str, int size, String padStr)` | Right pad a String with a specified String.
    `static String[]` | `split​(String str)` | Splits the provided text into an array, using whitespace as the separator.
    `static String[]` | `split​(String str, char separatorChar)` | Splits the provided text into an array, separator specified.
    `static String[]` | `split​(String str, String separatorChars)` | Splits the provided text into an array, separators specified.
    `static String[]` | `split​(String str, String separatorChars, int max)` | Splits the provided text into an array with a maximum length, separators specified.
    `static String[]` | `splitByCharacterType​(String str)` | Splits a String by Character type as returned by `java.lang.Character.getType(char)`.
    `static String[]` | `splitByCharacterTypeCamelCase​(String str)` | Splits a String by Character type as returned by `java.lang.Character.getType(char)`.
    `static String[]` | `splitByWholeSeparator​(String str, String separator)` | Splits the provided text into an array, separator string specified.
    `static String[]` | `splitByWholeSeparator​(String str, String separator, int max)` | Splits the provided text into an array, separator string specified.
    `static String[]` | `splitByWholeSeparatorPreserveAllTokens​(String str, String separator)` | Splits the provided text into an array, separator string specified.
    `static String[]` | `splitByWholeSeparatorPreserveAllTokens​(String str, String separator, int max)` | Splits the provided text into an array, separator string specified.
    `static String[]` | `splitPreserveAllTokens​(String str)` | Splits the provided text into an array, using whitespace as the separator, preserving all tokens, including empty tokens created by adjacent separators.
    `static String[]` | `splitPreserveAllTokens​(String str, char separatorChar)` | Splits the provided text into an array, separator specified, preserving all tokens, including empty tokens created by adjacent separators.
    `static String[]` | `splitPreserveAllTokens​(String str, String separatorChars)` | Splits the provided text into an array, separators specified, preserving all tokens, including empty tokens created by adjacent separators.
    `static String[]` | `splitPreserveAllTokens​(String str, String separatorChars, int max)` | Splits the provided text into an array with a maximum length, separators specified, preserving all tokens, including empty tokens created by adjacent separators.
    `static boolean` | `startsWith​(String str, String prefix)` | Check if a String starts with a specified prefix.
    `static boolean` | `startsWithAny​(String string, String[] searchStrings)` | Check if a String starts with any of an array of specified strings.
    `static boolean` | `startsWithIgnoreCase​(String str, String prefix)` | Case insensitive check if a String starts with a specified prefix.
    `static String` | `strip​(String str)` | Strips whitespace from the start and end of a String.
    `static String` | `strip​(String str, String stripChars)` | Strips any of a set of characters from the start and end of a String.
    `static String[]` | `stripAll​(String[] strs)` | Strips whitespace from the start and end of every String in an array.
    `static String[]` | `stripAll​(String[] strs, String stripChars)` | Strips any of a set of characters from the start and end of every String in an array.
    `static String` | `stripEnd​(String str, String stripChars)` | Strips any of a set of characters from the end of a String.
    `static String` | `stripStart​(String str, String stripChars)` | Strips any of a set of characters from the start of a String.
    `static String` | `stripToEmpty​(String str)` | Strips whitespace from the start and end of a String returning an empty String if `null` input.
    `static String` | `stripToNull​(String str)` | Strips whitespace from the start and end of a String returning `null` if the String is empty ("") after the strip.
    `static String` | `substring​(String str, int start)` | Gets a substring from the specified String avoiding exceptions.
    `static String` | `substring​(String str, int start, int end)` | Gets a substring from the specified String avoiding exceptions.
    `static String` | `substringAfter​(String str, String separator)` | Gets the substring after the first occurrence of a separator.
    `static String` | `substringAfterLast​(String str, String separator)` | Gets the substring after the last occurrence of a separator.
    `static String` | `substringBefore​(String str, String separator)` | Gets the substring before the first occurrence of a separator.
    `static String` | `substringBeforeLast​(String str, String separator)` | Gets the substring before the last occurrence of a separator.
    `static String` | `substringBetween​(String str, String tag)` | Gets the String that is nested in between two instances of the same String.
    `static String` | `substringBetween​(String str, String open, String close)` | Gets the String that is nested in between two Strings.
    `static String[]` | `substringsBetween​(String str, String open, String close)` | Searches a String for substrings delimited by a start and end tag, returning all matching substrings in an array.
    `static String` | `swapCase​(String str)` | Swaps the case of a String changing upper and title case to lower case, and lower case to upper case.
    `static String` | `trim​(String str)` | Removes control characters (char <= 32) from both ends of this String, handling `null` by returning `null`.
    `static String` | `trimToEmpty​(String str)` | Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty ("") after the trim or if it is `null`.
    `static String` | `trimToNull​(String str)` | Removes control characters (char <= 32) from both ends of this String returning `null` if the String is empty ("") after the trim or if it is `null`.
    `static String` | `uncapitalise​(String str)` | Deprecated. Use the standardly named `uncapitalize(String)`.
    `static String` | `uncapitalize​(String str)` | Uncapitalizes a String changing the first letter to title case as per `Character.toLowerCase(char)`.
    `static String` | `upperCase​(String str)` | Converts a String to upper case as per `String.toUpperCase()`.
    `static String` | `upperCase​(String str, Locale locale)` | Converts a String to upper case as per `String.toUpperCase(Locale)`.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### EMPTY

          public static final String EMPTY

      The empty String `""`.
      Since:
        2.0
      See Also:
        Constant Field Values

    - #### INDEX_NOT_FOUND

          public static final int INDEX_NOT_FOUND

      Represents a failed index search.
      Since:
        2.1
      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### StringUtils

          public StringUtils()

      `StringUtils` instances should NOT be constructed in standard programming. Instead, the class should be used as `StringUtils.trim(" foo ");`.

      This constructor is public to permit tools that require a JavaBean instance to operate.

  - ### Method Detail

    - #### isEmpty

          public static boolean isEmpty​(String str)

      Checks if a String is empty ("") or null.

           StringUtils.isEmpty(null)      = true
           StringUtils.isEmpty("")        = true
           StringUtils.isEmpty(" ")       = false
           StringUtils.isEmpty("bob")     = false
           StringUtils.isEmpty("  bob  ") = false

      NOTE: This method changed in Lang version 2.0. It no longer trims the String. That functionality is available in isBlank().

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if the String is empty or null

    - #### isNotEmpty

          public static boolean isNotEmpty​(String str)

      Checks if a String is not empty ("") and not null.

           StringUtils.isNotEmpty(null)      = false
           StringUtils.isNotEmpty("")        = false
           StringUtils.isNotEmpty(" ")       = true
           StringUtils.isNotEmpty("bob")     = true
           StringUtils.isNotEmpty("  bob  ") = true

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if the String is not empty and not null

    - #### isBlank

          public static boolean isBlank​(String str)

      Checks if a String is whitespace, empty ("") or null.

           StringUtils.isBlank(null)      = true
           StringUtils.isBlank("")        = true
           StringUtils.isBlank(" ")       = true
           StringUtils.isBlank("bob")     = false
           StringUtils.isBlank("  bob  ") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if the String is null, empty or whitespace
      Since:
        2.0

    - #### isNotBlank

          public static boolean isNotBlank​(String str)

      Checks if a String is not empty (""), not null and not whitespace only.

           StringUtils.isNotBlank(null)      = false
           StringUtils.isNotBlank("")        = false
           StringUtils.isNotBlank(" ")       = false
           StringUtils.isNotBlank("bob")     = true
           StringUtils.isNotBlank("  bob  ") = true

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if the String is not empty and not null and not whitespace
      Since:
        2.0

    - #### clean

          public static String clean​(String str)

      Deprecated.
      Use the clearer named `trimToEmpty(String)`. Method will be removed in Commons Lang 3.0.

      Removes control characters (char <= 32) from both ends of this String, handling `null` by returning an empty String ("").

           StringUtils.clean(null)          = ""
           StringUtils.clean("")            = ""
           StringUtils.clean("abc")         = "abc"
           StringUtils.clean("    abc    ") = "abc"
           StringUtils.clean("     ")       = ""

      Parameters:
        `str` - the String to clean, may be null
      Returns:
        the trimmed text, never `null`
      See Also:
        `String.trim()`

    - #### trim

          public static String trim​(String str)

      Removes control characters (char <= 32) from both ends of this String, handling `null` by returning `null`.

      The String is trimmed using `String.trim()`. Trim removes start and end characters <= 32. To strip whitespace use `strip(String)`.

      To trim your choice of characters, use the `strip(String, String)` methods.

           StringUtils.trim(null)          = null
           StringUtils.trim("")            = ""
           StringUtils.trim("     ")       = ""
           StringUtils.trim("abc")         = "abc"
           StringUtils.trim("    abc    ") = "abc"

      Parameters:
        `str` - the String to be trimmed, may be null
      Returns:
        the trimmed string, `null` if null String input

    - #### trimToNull

          public static String trimToNull​(String str)

      Removes control characters (char <= 32) from both ends of this String returning `null` if the String is empty ("") after the trim or if it is `null`.

      The String is trimmed using `String.trim()`. Trim removes start and end characters <= 32. To strip whitespace use `stripToNull(String)`.

           StringUtils.trimToNull(null)          = null
           StringUtils.trimToNull("")            = null
           StringUtils.trimToNull("     ")       = null
           StringUtils.trimToNull("abc")         = "abc"
           StringUtils.trimToNull("    abc    ") = "abc"

      Parameters:
        `str` - the String to be trimmed, may be null
      Returns:
        the trimmed String, `null` if only chars <= 32, empty or null String input
      Since:
        2.0

    - #### trimToEmpty

          public static String trimToEmpty​(String str)

      Removes control characters (char <= 32) from both ends of this String returning an empty String ("") if the String is empty ("") after the trim or if it is `null`.

      The String is trimmed using `String.trim()`. Trim removes start and end characters <= 32. To strip whitespace use `stripToEmpty(String)`.

           StringUtils.trimToEmpty(null)          = ""
           StringUtils.trimToEmpty("")            = ""
           StringUtils.trimToEmpty("     ")       = ""
           StringUtils.trimToEmpty("abc")         = "abc"
           StringUtils.trimToEmpty("    abc    ") = "abc"

      Parameters:
        `str` - the String to be trimmed, may be null
      Returns:
        the trimmed String, or an empty String if `null` input
      Since:
        2.0

    - #### strip

          public static String strip​(String str)

      Strips whitespace from the start and end of a String.

      This is similar to `trim(String)` but removes whitespace. Whitespace is defined by `Character.isWhitespace(char)`.

      A `null` input String returns `null`.

           StringUtils.strip(null)     = null
           StringUtils.strip("")       = ""
           StringUtils.strip("   ")    = ""
           StringUtils.strip("abc")    = "abc"
           StringUtils.strip("  abc")  = "abc"
           StringUtils.strip("abc  ")  = "abc"
           StringUtils.strip(" abc ")  = "abc"
           StringUtils.strip(" ab c ") = "ab c"

      Parameters:
        `str` - the String to remove whitespace from, may be null
      Returns:
        the stripped String, `null` if null String input

    - #### stripToNull

          public static String stripToNull​(String str)

      Strips whitespace from the start and end of a String returning `null` if the String is empty ("") after the strip.

      This is similar to `trimToNull(String)` but removes whitespace. Whitespace is defined by `Character.isWhitespace(char)`.

           StringUtils.stripToNull(null)     = null
           StringUtils.stripToNull("")       = null
           StringUtils.stripToNull("   ")    = null
           StringUtils.stripToNull("abc")    = "abc"
           StringUtils.stripToNull("  abc")  = "abc"
           StringUtils.stripToNull("abc  ")  = "abc"
           StringUtils.stripToNull(" abc ")  = "abc"
           StringUtils.stripToNull(" ab c ") = "ab c"

      Parameters:
        `str` - the String to be stripped, may be null
      Returns:
        the stripped String, `null` if whitespace, empty or null String input
      Since:
        2.0

    - #### stripToEmpty

          public static String stripToEmpty​(String str)

      Strips whitespace from the start and end of a String returning an empty String if `null` input.

      This is similar to `trimToEmpty(String)` but removes whitespace. Whitespace is defined by `Character.isWhitespace(char)`.

           StringUtils.stripToEmpty(null)     = ""
           StringUtils.stripToEmpty("")       = ""
           StringUtils.stripToEmpty("   ")    = ""
           StringUtils.stripToEmpty("abc")    = "abc"
           StringUtils.stripToEmpty("  abc")  = "abc"
           StringUtils.stripToEmpty("abc  ")  = "abc"
           StringUtils.stripToEmpty(" abc ")  = "abc"
           StringUtils.stripToEmpty(" ab c ") = "ab c"

      Parameters:
        `str` - the String to be stripped, may be null
      Returns:
        the trimmed String, or an empty String if `null` input
      Since:
        2.0

    - #### strip

          public static String strip​(String str,
                                     String stripChars)

      Strips any of a set of characters from the start and end of a String. This is similar to `String.trim()` but allows the characters to be stripped to be controlled.

      A `null` input String returns `null`. An empty string ("") input returns the empty string.

      If the stripChars String is `null`, whitespace is stripped as defined by `Character.isWhitespace(char)`. Alternatively use `strip(String)`.

           StringUtils.strip(null, *)          = null
           StringUtils.strip("", *)            = ""
           StringUtils.strip("abc", null)      = "abc"
           StringUtils.strip("  abc", null)    = "abc"
           StringUtils.strip("abc  ", null)    = "abc"
           StringUtils.strip(" abc ", null)    = "abc"
           StringUtils.strip("  abcyx", "xyz") = "  abc"

      Parameters:
        `str` - the String to remove characters from, may be null
        `stripChars` - the characters to remove, null treated as whitespace
      Returns:
        the stripped String, `null` if null String input

    - #### stripStart

          public static String stripStart​(String str,
                                          String stripChars)

      Strips any of a set of characters from the start of a String.

      A `null` input String returns `null`. An empty string ("") input returns the empty string.

      If the stripChars String is `null`, whitespace is stripped as defined by `Character.isWhitespace(char)`.

           StringUtils.stripStart(null, *)          = null
           StringUtils.stripStart("", *)            = ""
           StringUtils.stripStart("abc", "")        = "abc"
           StringUtils.stripStart("abc", null)      = "abc"
           StringUtils.stripStart("  abc", null)    = "abc"
           StringUtils.stripStart("abc  ", null)    = "abc  "
           StringUtils.stripStart(" abc ", null)    = "abc "
           StringUtils.stripStart("yxabc  ", "xyz") = "abc  "

      Parameters:
        `str` - the String to remove characters from, may be null
        `stripChars` - the characters to remove, null treated as whitespace
      Returns:
        the stripped String, `null` if null String input

    - #### stripEnd

          public static String stripEnd​(String str,
                                        String stripChars)

      Strips any of a set of characters from the end of a String.

      A `null` input String returns `null`. An empty string ("") input returns the empty string.

      If the stripChars String is `null`, whitespace is stripped as defined by `Character.isWhitespace(char)`.

           StringUtils.stripEnd(null, *)          = null
           StringUtils.stripEnd("", *)            = ""
           StringUtils.stripEnd("abc", "")        = "abc"
           StringUtils.stripEnd("abc", null)      = "abc"
           StringUtils.stripEnd("  abc", null)    = "  abc"
           StringUtils.stripEnd("abc  ", null)    = "abc"
           StringUtils.stripEnd(" abc ", null)    = " abc"
           StringUtils.stripEnd("  abcyx", "xyz") = "  abc"
           StringUtils.stripEnd("120.00", ".0")   = "12"

      Parameters:
        `str` - the String to remove characters from, may be null
        `stripChars` - the set of characters to remove, null treated as whitespace
      Returns:
        the stripped String, `null` if null String input

    - #### stripAll

          public static String[] stripAll​(String[] strs)

      Strips whitespace from the start and end of every String in an array. Whitespace is defined by `Character.isWhitespace(char)`.

      A new array is returned each time, except for length zero. A `null` array will return `null`. An empty array will return itself. A `null` array entry will be ignored.

           StringUtils.stripAll(null)             = null
           StringUtils.stripAll([])               = []
           StringUtils.stripAll(["abc", "  abc"]) = ["abc", "abc"]
           StringUtils.stripAll(["abc  ", null])  = ["abc", null]

      Parameters:
        `strs` - the array to remove whitespace from, may be null
      Returns:
        the stripped Strings, `null` if null array input

    - #### stripAll

          public static String[] stripAll​(String[] strs,
                                          String stripChars)

      Strips any of a set of characters from the start and end of every String in an array.

      Whitespace is defined by `Character.isWhitespace(char)`.

      A new array is returned each time, except for length zero. A `null` array will return `null`. An empty array will return itself. A `null` array entry will be ignored. A `null` stripChars will strip whitespace as defined by `Character.isWhitespace(char)`.

           StringUtils.stripAll(null, *)                = null
           StringUtils.stripAll([], *)                  = []
           StringUtils.stripAll(["abc", "  abc"], null) = ["abc", "abc"]
           StringUtils.stripAll(["abc  ", null], null)  = ["abc", null]
           StringUtils.stripAll(["abc  ", null], "yz")  = ["abc  ", null]
           StringUtils.stripAll(["yabcz", null], "yz")  = ["abc", null]

      Parameters:
        `strs` - the array to remove characters from, may be null
        `stripChars` - the characters to remove, null treated as whitespace
      Returns:
        the stripped Strings, `null` if null array input

    - #### equals

          public static boolean equals​(String str1,
                                       String str2)

      Compares two Strings, returning `true` if they are equal.

      `null`s are handled without exceptions. Two `null` references are considered to be equal. The comparison is case sensitive.

           StringUtils.equals(null, null)   = true
           StringUtils.equals(null, "abc")  = false
           StringUtils.equals("abc", null)  = false
           StringUtils.equals("abc", "abc") = true
           StringUtils.equals("abc", "ABC") = false

      Parameters:
        `str1` - the first String, may be null
        `str2` - the second String, may be null
      Returns:
        `true` if the Strings are equal, case sensitive, or both `null`
      See Also:
        `String.equals(Object)`

    - #### equalsIgnoreCase

          public static boolean equalsIgnoreCase​(String str1,
                                                 String str2)

      Compares two Strings, returning `true` if they are equal ignoring the case.

      `null`s are handled without exceptions. Two `null` references are considered equal. Comparison is case insensitive.

           StringUtils.equalsIgnoreCase(null, null)   = true
           StringUtils.equalsIgnoreCase(null, "abc")  = false
           StringUtils.equalsIgnoreCase("abc", null)  = false
           StringUtils.equalsIgnoreCase("abc", "abc") = true
           StringUtils.equalsIgnoreCase("abc", "ABC") = true

      Parameters:
        `str1` - the first String, may be null
        `str2` - the second String, may be null
      Returns:
        `true` if the Strings are equal, case insensitive, or both `null`
      See Also:
        `String.equalsIgnoreCase(String)`

    - #### indexOf

          public static int indexOf​(String str,
                                    char searchChar)

      Finds the first index within a String, handling `null`. This method uses `String.indexOf(int)`.

      A `null` or empty ("") String will return `INDEX_NOT_FOUND (-1)`.

           StringUtils.indexOf(null, *)         = -1
           StringUtils.indexOf("", *)           = -1
           StringUtils.indexOf("aabaabaa", 'a') = 0
           StringUtils.indexOf("aabaabaa", 'b') = 2

      Parameters:
        `str` - the String to check, may be null
        `searchChar` - the character to find
      Returns:
        the first index of the search character, -1 if no match or `null` string input
      Since:
        2.0

    - #### indexOf

          public static int indexOf​(String str,
                                    char searchChar,
                                    int startPos)

      Finds the first index within a String from a start position, handling `null`. This method uses `String.indexOf(int, int)`.

      A `null` or empty ("") String will return `(INDEX_NOT_FOUND) -1`. A negative start position is treated as zero. A start position greater than the string length returns `-1`.

           StringUtils.indexOf(null, *, *)          = -1
           StringUtils.indexOf("", *, *)            = -1
           StringUtils.indexOf("aabaabaa", 'b', 0)  = 2
           StringUtils.indexOf("aabaabaa", 'b', 3)  = 5
           StringUtils.indexOf("aabaabaa", 'b', 9)  = -1
           StringUtils.indexOf("aabaabaa", 'b', -1) = 2

      Parameters:
        `str` - the String to check, may be null
        `searchChar` - the character to find
        `startPos` - the start position, negative treated as zero
      Returns:
        the first index of the search character, -1 if no match or `null` string input
      Since:
        2.0

    - #### indexOf

          public static int indexOf​(String str,
                                    String searchStr)

      Finds the first index within a String, handling `null`. This method uses `String.indexOf(String)`.

      A `null` String will return `-1`.

           StringUtils.indexOf(null, *)          = -1
           StringUtils.indexOf(*, null)          = -1
           StringUtils.indexOf("", "")           = 0
           StringUtils.indexOf("", *)            = -1 (except when * = "")
           StringUtils.indexOf("aabaabaa", "a")  = 0
           StringUtils.indexOf("aabaabaa", "b")  = 2
           StringUtils.indexOf("aabaabaa", "ab") = 1
           StringUtils.indexOf("aabaabaa", "")   = 0

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.0

    - #### ordinalIndexOf

          public static int ordinalIndexOf​(String str,
                                           String searchStr,
                                           int ordinal)

      Finds the n-th index within a String, handling `null`. This method uses `String.indexOf(String)`.

      A `null` String will return `-1`.

           StringUtils.ordinalIndexOf(null, *, *)          = -1
           StringUtils.ordinalIndexOf(*, null, *)          = -1
           StringUtils.ordinalIndexOf("", "", *)           = 0
           StringUtils.ordinalIndexOf("aabaabaa", "a", 1)  = 0
           StringUtils.ordinalIndexOf("aabaabaa", "a", 2)  = 1
           StringUtils.ordinalIndexOf("aabaabaa", "b", 1)  = 2
           StringUtils.ordinalIndexOf("aabaabaa", "b", 2)  = 5
           StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1
           StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4
           StringUtils.ordinalIndexOf("aabaabaa", "", 1)   = 0
           StringUtils.ordinalIndexOf("aabaabaa", "", 2)   = 0

      Note that 'head(String str, int n)' may be implemented as:

             str.substring(0, lastOrdinalIndexOf(str, "\n", n))

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `ordinal` - the n-th `searchStr` to find
      Returns:
        the n-th index of the search String, `-1` (`INDEX_NOT_FOUND`) if no match or `null` string input
      Since:
        2.1

    - #### indexOf

          public static int indexOf​(String str,
                                    String searchStr,
                                    int startPos)

      Finds the first index within a String, handling `null`. This method uses `String.indexOf(String, int)`.

      A `null` String will return `-1`. A negative start position is treated as zero. An empty ("") search String always matches. A start position greater than the string length only matches an empty search String.

           StringUtils.indexOf(null, *, *)          = -1
           StringUtils.indexOf(*, null, *)          = -1
           StringUtils.indexOf("", "", 0)           = 0
           StringUtils.indexOf("", *, 0)            = -1 (except when * = "")
           StringUtils.indexOf("aabaabaa", "a", 0)  = 0
           StringUtils.indexOf("aabaabaa", "b", 0)  = 2
           StringUtils.indexOf("aabaabaa", "ab", 0) = 1
           StringUtils.indexOf("aabaabaa", "b", 3)  = 5
           StringUtils.indexOf("aabaabaa", "b", 9)  = -1
           StringUtils.indexOf("aabaabaa", "b", -1) = 2
           StringUtils.indexOf("aabaabaa", "", 2)   = 2
           StringUtils.indexOf("abc", "", 9)        = 3

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `startPos` - the start position, negative treated as zero
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.0

    - #### indexOfIgnoreCase

          public static int indexOfIgnoreCase​(String str,
                                              String searchStr)

      Case in-sensitive find of the first index within a String.

      A `null` String will return `-1`. A negative start position is treated as zero. An empty ("") search String always matches. A start position greater than the string length only matches an empty search String.

           StringUtils.indexOfIgnoreCase(null, *)          = -1
           StringUtils.indexOfIgnoreCase(*, null)          = -1
           StringUtils.indexOfIgnoreCase("", "")           = 0
           StringUtils.indexOfIgnoreCase("aabaabaa", "a")  = 0
           StringUtils.indexOfIgnoreCase("aabaabaa", "b")  = 2
           StringUtils.indexOfIgnoreCase("aabaabaa", "ab") = 1

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.5

    - #### indexOfIgnoreCase

          public static int indexOfIgnoreCase​(String str,
                                              String searchStr,
                                              int startPos)

      Case in-sensitive find of the first index within a String from the specified position.

      A `null` String will return `-1`. A negative start position is treated as zero. An empty ("") search String always matches. A start position greater than the string length only matches an empty search String.

           StringUtils.indexOfIgnoreCase(null, *, *)          = -1
           StringUtils.indexOfIgnoreCase(*, null, *)          = -1
           StringUtils.indexOfIgnoreCase("", "", 0)           = 0
           StringUtils.indexOfIgnoreCase("aabaabaa", "A", 0)  = 0
           StringUtils.indexOfIgnoreCase("aabaabaa", "B", 0)  = 2
           StringUtils.indexOfIgnoreCase("aabaabaa", "AB", 0) = 1
           StringUtils.indexOfIgnoreCase("aabaabaa", "B", 3)  = 5
           StringUtils.indexOfIgnoreCase("aabaabaa", "B", 9)  = -1
           StringUtils.indexOfIgnoreCase("aabaabaa", "B", -1) = 2
           StringUtils.indexOfIgnoreCase("aabaabaa", "", 2)   = 2
           StringUtils.indexOfIgnoreCase("abc", "", 9)        = 3

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `startPos` - the start position, negative treated as zero
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.5

    - #### lastIndexOf

          public static int lastIndexOf​(String str,
                                        char searchChar)

      Finds the last index within a String, handling `null`. This method uses `String.lastIndexOf(int)`.

      A `null` or empty ("") String will return `-1`.

           StringUtils.lastIndexOf(null, *)         = -1
           StringUtils.lastIndexOf("", *)           = -1
           StringUtils.lastIndexOf("aabaabaa", 'a') = 7
           StringUtils.lastIndexOf("aabaabaa", 'b') = 5

      Parameters:
        `str` - the String to check, may be null
        `searchChar` - the character to find
      Returns:
        the last index of the search character, -1 if no match or `null` string input
      Since:
        2.0

    - #### lastIndexOf

          public static int lastIndexOf​(String str,
                                        char searchChar,
                                        int startPos)

      Finds the last index within a String from a start position, handling `null`. This method uses `String.lastIndexOf(int, int)`.

      A `null` or empty ("") String will return `-1`. A negative start position returns `-1`. A start position greater than the string length searches the whole string.

           StringUtils.lastIndexOf(null, *, *)          = -1
           StringUtils.lastIndexOf("", *,  *)           = -1
           StringUtils.lastIndexOf("aabaabaa", 'b', 8)  = 5
           StringUtils.lastIndexOf("aabaabaa", 'b', 4)  = 2
           StringUtils.lastIndexOf("aabaabaa", 'b', 0)  = -1
           StringUtils.lastIndexOf("aabaabaa", 'b', 9)  = 5
           StringUtils.lastIndexOf("aabaabaa", 'b', -1) = -1
           StringUtils.lastIndexOf("aabaabaa", 'a', 0)  = 0

      Parameters:
        `str` - the String to check, may be null
        `searchChar` - the character to find
        `startPos` - the start position
      Returns:
        the last index of the search character, -1 if no match or `null` string input
      Since:
        2.0

    - #### lastIndexOf

          public static int lastIndexOf​(String str,
                                        String searchStr)

      Finds the last index within a String, handling `null`. This method uses `String.lastIndexOf(String)`.

      A `null` String will return `-1`.

           StringUtils.lastIndexOf(null, *)          = -1
           StringUtils.lastIndexOf(*, null)          = -1
           StringUtils.lastIndexOf("", "")           = 0
           StringUtils.lastIndexOf("aabaabaa", "a")  = 7
           StringUtils.lastIndexOf("aabaabaa", "b")  = 5
           StringUtils.lastIndexOf("aabaabaa", "ab") = 4
           StringUtils.lastIndexOf("aabaabaa", "")   = 8

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        the last index of the search String, -1 if no match or `null` string input
      Since:
        2.0

    - #### lastOrdinalIndexOf

          public static int lastOrdinalIndexOf​(String str,
                                               String searchStr,
                                               int ordinal)

      Finds the n-th last index within a String, handling `null`. This method uses `String.lastIndexOf(String)`.

      A `null` String will return `-1`.

           StringUtils.lastOrdinalIndexOf(null, *, *)          = -1
           StringUtils.lastOrdinalIndexOf(*, null, *)          = -1
           StringUtils.lastOrdinalIndexOf("", "", *)           = 0
           StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1)  = 7
           StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2)  = 6
           StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1)  = 5
           StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2)  = 2
           StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4
           StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1
           StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1)   = 8
           StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2)   = 8

      Note that 'tail(String str, int n)' may be implemented as:

             str.substring(lastOrdinalIndexOf(str, "\n", n) + 1)

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `ordinal` - the n-th last `searchStr` to find
      Returns:
        the n-th last index of the search String, `-1` (`INDEX_NOT_FOUND`) if no match or `null` string input
      Since:
        2.5

    - #### lastIndexOf

          public static int lastIndexOf​(String str,
                                        String searchStr,
                                        int startPos)

      Finds the first index within a String, handling `null`. This method uses `String.lastIndexOf(String, int)`.

      A `null` String will return `-1`. A negative start position returns `-1`. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.

           StringUtils.lastIndexOf(null, *, *)          = -1
           StringUtils.lastIndexOf(*, null, *)          = -1
           StringUtils.lastIndexOf("aabaabaa", "a", 8)  = 7
           StringUtils.lastIndexOf("aabaabaa", "b", 8)  = 5
           StringUtils.lastIndexOf("aabaabaa", "ab", 8) = 4
           StringUtils.lastIndexOf("aabaabaa", "b", 9)  = 5
           StringUtils.lastIndexOf("aabaabaa", "b", -1) = -1
           StringUtils.lastIndexOf("aabaabaa", "a", 0)  = 0
           StringUtils.lastIndexOf("aabaabaa", "b", 0)  = -1

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `startPos` - the start position, negative treated as zero
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.0

    - #### lastIndexOfIgnoreCase

          public static int lastIndexOfIgnoreCase​(String str,
                                                  String searchStr)

      Case in-sensitive find of the last index within a String.

      A `null` String will return `-1`. A negative start position returns `-1`. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.

           StringUtils.lastIndexOfIgnoreCase(null, *)          = -1
           StringUtils.lastIndexOfIgnoreCase(*, null)          = -1
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A")  = 7
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B")  = 5
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB") = 4

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.5

    - #### lastIndexOfIgnoreCase

          public static int lastIndexOfIgnoreCase​(String str,
                                                  String searchStr,
                                                  int startPos)

      Case in-sensitive find of the last index within a String from the specified position.

      A `null` String will return `-1`. A negative start position returns `-1`. An empty ("") search String always matches unless the start position is negative. A start position greater than the string length searches the whole string.

           StringUtils.lastIndexOfIgnoreCase(null, *, *)          = -1
           StringUtils.lastIndexOfIgnoreCase(*, null, *)          = -1
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 8)  = 7
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 8)  = 5
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "AB", 8) = 4
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 9)  = 5
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", -1) = -1
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "A", 0)  = 0
           StringUtils.lastIndexOfIgnoreCase("aabaabaa", "B", 0)  = -1

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
        `startPos` - the start position
      Returns:
        the first index of the search String, -1 if no match or `null` string input
      Since:
        2.5

    - #### contains

          public static boolean contains​(String str,
                                         char searchChar)

      Checks if String contains a search character, handling `null`. This method uses `String.indexOf(int)`.

      A `null` or empty ("") String will return `false`.

           StringUtils.contains(null, *)    = false
           StringUtils.contains("", *)      = false
           StringUtils.contains("abc", 'a') = true
           StringUtils.contains("abc", 'z') = false

      Parameters:
        `str` - the String to check, may be null
        `searchChar` - the character to find
      Returns:
        true if the String contains the search character, false if not or `null` string input
      Since:
        2.0

    - #### contains

          public static boolean contains​(String str,
                                         String searchStr)

      Checks if String contains a search String, handling `null`. This method uses `String.indexOf(String)`.

      A `null` String will return `false`.

           StringUtils.contains(null, *)     = false
           StringUtils.contains(*, null)     = false
           StringUtils.contains("", "")      = true
           StringUtils.contains("abc", "")   = true
           StringUtils.contains("abc", "a")  = true
           StringUtils.contains("abc", "z")  = false

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        true if the String contains the search String, false if not or `null` string input
      Since:
        2.0

    - #### containsIgnoreCase

          public static boolean containsIgnoreCase​(String str,
                                                   String searchStr)

      Checks if String contains a search String irrespective of case, handling `null`. Case-insensitivity is defined as by `String.equalsIgnoreCase(String)`.

      A `null` String will return `false`.

           StringUtils.contains(null, *) = false
           StringUtils.contains(*, null) = false
           StringUtils.contains("", "") = true
           StringUtils.contains("abc", "") = true
           StringUtils.contains("abc", "a") = true
           StringUtils.contains("abc", "z") = false
           StringUtils.contains("abc", "A") = true
           StringUtils.contains("abc", "Z") = false

      Parameters:
        `str` - the String to check, may be null
        `searchStr` - the String to find, may be null
      Returns:
        true if the String contains the search String irrespective of case or false if not or `null` string input

    - #### indexOfAny

          public static int indexOfAny​(String str,
                                       char[] searchChars)

      Search a String to find the first index of any character in the given set of characters.

      A `null` String will return `-1`. A `null` or zero length search array will return `-1`.

           StringUtils.indexOfAny(null, *)                = -1
           StringUtils.indexOfAny("", *)                  = -1
           StringUtils.indexOfAny(*, null)                = -1
           StringUtils.indexOfAny(*, [])                  = -1
           StringUtils.indexOfAny("zzabyycdxx",['z','a']) = 0
           StringUtils.indexOfAny("zzabyycdxx",['b','y']) = 3
           StringUtils.indexOfAny("aba", ['z'])           = -1

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the index of any of the chars, -1 if no match or null input
      Since:
        2.0

    - #### indexOfAny

          public static int indexOfAny​(String str,
                                       String searchChars)

      Search a String to find the first index of any character in the given set of characters.

      A `null` String will return `-1`. A `null` search string will return `-1`.

           StringUtils.indexOfAny(null, *)            = -1
           StringUtils.indexOfAny("", *)              = -1
           StringUtils.indexOfAny(*, null)            = -1
           StringUtils.indexOfAny(*, "")              = -1
           StringUtils.indexOfAny("zzabyycdxx", "za") = 0
           StringUtils.indexOfAny("zzabyycdxx", "by") = 3
           StringUtils.indexOfAny("aba","z")          = -1

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the index of any of the chars, -1 if no match or null input
      Since:
        2.0

    - #### containsAny

          public static boolean containsAny​(String str,
                                            char[] searchChars)

      Checks if the String contains any character in the given set of characters.

      A `null` String will return `false`. A `null` or zero length search array will return `false`.

           StringUtils.containsAny(null, *)                = false
           StringUtils.containsAny("", *)                  = false
           StringUtils.containsAny(*, null)                = false
           StringUtils.containsAny(*, [])                  = false
           StringUtils.containsAny("zzabyycdxx",['z','a']) = true
           StringUtils.containsAny("zzabyycdxx",['b','y']) = true
           StringUtils.containsAny("aba", ['z'])           = false

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the `true` if any of the chars are found, `false` if no match or null input
      Since:
        2.4

    - #### containsAny

          public static boolean containsAny​(String str,
                                            String searchChars)

      Checks if the String contains any character in the given set of characters.

      A `null` String will return `false`. A `null` search string will return `false`.

           StringUtils.containsAny(null, *)            = false
           StringUtils.containsAny("", *)              = false
           StringUtils.containsAny(*, null)            = false
           StringUtils.containsAny(*, "")              = false
           StringUtils.containsAny("zzabyycdxx", "za") = true
           StringUtils.containsAny("zzabyycdxx", "by") = true
           StringUtils.containsAny("aba","z")          = false

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the `true` if any of the chars are found, `false` if no match or null input
      Since:
        2.4

    - #### indexOfAnyBut

          public static int indexOfAnyBut​(String str,
                                          char[] searchChars)

      Search a String to find the first index of any character not in the given set of characters.

      A `null` String will return `-1`. A `null` or zero length search array will return `-1`.

           StringUtils.indexOfAnyBut(null, *)                              = -1
           StringUtils.indexOfAnyBut("", *)                                = -1
           StringUtils.indexOfAnyBut(*, null)                              = -1
           StringUtils.indexOfAnyBut(*, [])                                = -1
           StringUtils.indexOfAnyBut("zzabyycdxx", new char[] {'z', 'a'} ) = 3
           StringUtils.indexOfAnyBut("aba", new char[] {'z'} )             = 0
           StringUtils.indexOfAnyBut("aba", new char[] {'a', 'b'} )        = -1

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the index of any of the chars, -1 if no match or null input
      Since:
        2.0

    - #### indexOfAnyBut

          public static int indexOfAnyBut​(String str,
                                          String searchChars)

      Search a String to find the first index of any character not in the given set of characters.

      A `null` String will return `-1`. A `null` or empty search string will return `-1`.

           StringUtils.indexOfAnyBut(null, *)            = -1
           StringUtils.indexOfAnyBut("", *)              = -1
           StringUtils.indexOfAnyBut(*, null)            = -1
           StringUtils.indexOfAnyBut(*, "")              = -1
           StringUtils.indexOfAnyBut("zzabyycdxx", "za") = 3
           StringUtils.indexOfAnyBut("zzabyycdxx", "")   = -1
           StringUtils.indexOfAnyBut("aba","ab")         = -1

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - the chars to search for, may be null
      Returns:
        the index of any of the chars, -1 if no match or null input
      Since:
        2.0

    - #### containsOnly

          public static boolean containsOnly​(String str,
                                             char[] valid)

      Checks if the String contains only certain characters.

      A `null` String will return `false`. A `null` valid character array will return `false`. An empty String (length()=0) always returns `true`.

           StringUtils.containsOnly(null, *)       = false
           StringUtils.containsOnly(*, null)       = false
           StringUtils.containsOnly("", *)         = true
           StringUtils.containsOnly("ab", '')      = false
           StringUtils.containsOnly("abab", 'abc') = true
           StringUtils.containsOnly("ab1", 'abc')  = false
           StringUtils.containsOnly("abz", 'abc')  = false

      Parameters:
        `str` - the String to check, may be null
        `valid` - an array of valid chars, may be null
      Returns:
        true if it only contains valid chars and is non-null

    - #### containsOnly

          public static boolean containsOnly​(String str,
                                             String validChars)

      Checks if the String contains only certain characters.

      A `null` String will return `false`. A `null` valid character String will return `false`. An empty String (length()=0) always returns `true`.

           StringUtils.containsOnly(null, *)       = false
           StringUtils.containsOnly(*, null)       = false
           StringUtils.containsOnly("", *)         = true
           StringUtils.containsOnly("ab", "")      = false
           StringUtils.containsOnly("abab", "abc") = true
           StringUtils.containsOnly("ab1", "abc")  = false
           StringUtils.containsOnly("abz", "abc")  = false

      Parameters:
        `str` - the String to check, may be null
        `validChars` - a String of valid chars, may be null
      Returns:
        true if it only contains valid chars and is non-null
      Since:
        2.0

    - #### containsNone

          public static boolean containsNone​(String str,
                                             char[] searchChars)

      Checks that the String does not contain certain characters.

      A `null` String will return `true`. A `null` invalid character array will return `true`. An empty String (length()=0) always returns true.

           StringUtils.containsNone(null, *)       = true
           StringUtils.containsNone(*, null)       = true
           StringUtils.containsNone("", *)         = true
           StringUtils.containsNone("ab", '')      = true
           StringUtils.containsNone("abab", 'xyz') = true
           StringUtils.containsNone("ab1", 'xyz')  = true
           StringUtils.containsNone("abz", 'xyz')  = false

      Parameters:
        `str` - the String to check, may be null
        `searchChars` - an array of invalid chars, may be null
      Returns:
        true if it contains none of the invalid chars, or is null
      Since:
        2.0

    - #### containsNone

          public static boolean containsNone​(String str,
                                             String invalidChars)

      Checks that the String does not contain certain characters.

      A `null` String will return `true`. A `null` invalid character array will return `true`. An empty String ("") always returns true.

           StringUtils.containsNone(null, *)       = true
           StringUtils.containsNone(*, null)       = true
           StringUtils.containsNone("", *)         = true
           StringUtils.containsNone("ab", "")      = true
           StringUtils.containsNone("abab", "xyz") = true
           StringUtils.containsNone("ab1", "xyz")  = true
           StringUtils.containsNone("abz", "xyz")  = false

      Parameters:
        `str` - the String to check, may be null
        `invalidChars` - a String of invalid chars, may be null
      Returns:
        true if it contains none of the invalid chars, or is null
      Since:
        2.0

    - #### indexOfAny

          public static int indexOfAny​(String str,
                                       String[] searchStrs)

      Find the first index of any of a set of potential substrings.

      A `null` String will return `-1`. A `null` or zero length search array will return `-1`. A `null` search array entry will be ignored, but a search array containing "" will return `0` if `str` is not null. This method uses `String.indexOf(String)`.

           StringUtils.indexOfAny(null, *)                     = -1
           StringUtils.indexOfAny(*, null)                     = -1
           StringUtils.indexOfAny(*, [])                       = -1
           StringUtils.indexOfAny("zzabyycdxx", ["ab","cd"])   = 2
           StringUtils.indexOfAny("zzabyycdxx", ["cd","ab"])   = 2
           StringUtils.indexOfAny("zzabyycdxx", ["mn","op"])   = -1
           StringUtils.indexOfAny("zzabyycdxx", ["zab","aby"]) = 1
           StringUtils.indexOfAny("zzabyycdxx", [""])          = 0
           StringUtils.indexOfAny("", [""])                    = 0
           StringUtils.indexOfAny("", ["a"])                   = -1

      Parameters:
        `str` - the String to check, may be null
        `searchStrs` - the Strings to search for, may be null
      Returns:
        the first index of any of the searchStrs in str, -1 if no match

    - #### lastIndexOfAny

          public static int lastIndexOfAny​(String str,
                                           String[] searchStrs)

      Find the latest index of any of a set of potential substrings.

      A `null` String will return `-1`. A `null` search array will return `-1`. A `null` or zero length search array entry will be ignored, but a search array containing "" will return the length of `str` if `str` is not null. This method uses `String.indexOf(String)`

           StringUtils.lastIndexOfAny(null, *)                   = -1
           StringUtils.lastIndexOfAny(*, null)                   = -1
           StringUtils.lastIndexOfAny(*, [])                     = -1
           StringUtils.lastIndexOfAny(*, [null])                 = -1
           StringUtils.lastIndexOfAny("zzabyycdxx", ["ab","cd"]) = 6
           StringUtils.lastIndexOfAny("zzabyycdxx", ["cd","ab"]) = 6
           StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
           StringUtils.lastIndexOfAny("zzabyycdxx", ["mn","op"]) = -1
           StringUtils.lastIndexOfAny("zzabyycdxx", ["mn",""])   = 10

      Parameters:
        `str` - the String to check, may be null
        `searchStrs` - the Strings to search for, may be null
      Returns:
        the last index of any of the Strings, -1 if no match

    - #### substring

          public static String substring​(String str,
                                         int start)

      Gets a substring from the specified String avoiding exceptions.

      A negative start position can be used to start `n` characters from the end of the String.

      A `null` String will return `null`. An empty ("") String will return "".

           StringUtils.substring(null, *)   = null
           StringUtils.substring("", *)     = ""
           StringUtils.substring("abc", 0)  = "abc"
           StringUtils.substring("abc", 2)  = "c"
           StringUtils.substring("abc", 4)  = ""
           StringUtils.substring("abc", -2) = "bc"
           StringUtils.substring("abc", -4) = "abc"

      Parameters:
        `str` - the String to get the substring from, may be null
        `start` - the position to start from, negative means count back from the end of the String by this many characters
      Returns:
        substring from start position, `null` if null String input

    - #### substring

          public static String substring​(String str,
                                         int start,
                                         int end)

      Gets a substring from the specified String avoiding exceptions.

      A negative start position can be used to start/end `n` characters from the end of the String.

      The returned substring starts with the character in the `start` position and ends before the `end` position. All position counting is zero-based -- i.e., to start at the beginning of the string use `start = 0`. Negative start and end positions can be used to specify offsets relative to the end of the String.

      If `start` is not strictly to the left of `end`, "" is returned.

           StringUtils.substring(null, *, *)    = null
           StringUtils.substring("", * ,  *)    = "";
           StringUtils.substring("abc", 0, 2)   = "ab"
           StringUtils.substring("abc", 2, 0)   = ""
           StringUtils.substring("abc", 2, 4)   = "c"
           StringUtils.substring("abc", 4, 6)   = ""
           StringUtils.substring("abc", 2, 2)   = ""
           StringUtils.substring("abc", -2, -1) = "b"
           StringUtils.substring("abc", -4, 2)  = "ab"

      Parameters:
        `str` - the String to get the substring from, may be null
        `start` - the position to start from, negative means count back from the end of the String by this many characters
        `end` - the position to end at (exclusive), negative means count back from the end of the String by this many characters
      Returns:
        substring from start position to end positon, `null` if null String input

    - #### left

          public static String left​(String str,
                                    int len)

      Gets the leftmost `len` characters of a String.

      If `len` characters are not available, or the String is `null`, the String will be returned without an exception. An empty String is returned if len is negative.

           StringUtils.left(null, *)    = null
           StringUtils.left(*, -ve)     = ""
           StringUtils.left("", *)      = ""
           StringUtils.left("abc", 0)   = ""
           StringUtils.left("abc", 2)   = "ab"
           StringUtils.left("abc", 4)   = "abc"

      Parameters:
        `str` - the String to get the leftmost characters from, may be null
        `len` - the length of the required String
      Returns:
        the leftmost characters, `null` if null String input

    - #### right

          public static String right​(String str,
                                     int len)

      Gets the rightmost `len` characters of a String.

      If `len` characters are not available, or the String is `null`, the String will be returned without an an exception. An empty String is returned if len is negative.

           StringUtils.right(null, *)    = null
           StringUtils.right(*, -ve)     = ""
           StringUtils.right("", *)      = ""
           StringUtils.right("abc", 0)   = ""
           StringUtils.right("abc", 2)   = "bc"
           StringUtils.right("abc", 4)   = "abc"

      Parameters:
        `str` - the String to get the rightmost characters from, may be null
        `len` - the length of the required String
      Returns:
        the rightmost characters, `null` if null String input

    - #### mid

          public static String mid​(String str,
                                   int pos,
                                   int len)

      Gets `len` characters from the middle of a String.

      If `len` characters are not available, the remainder of the String will be returned without an exception. If the String is `null`, `null` will be returned. An empty String is returned if len is negative or exceeds the length of `str`.

           StringUtils.mid(null, *, *)    = null
           StringUtils.mid(*, *, -ve)     = ""
           StringUtils.mid("", 0, *)      = ""
           StringUtils.mid("abc", 0, 2)   = "ab"
           StringUtils.mid("abc", 0, 4)   = "abc"
           StringUtils.mid("abc", 2, 4)   = "c"
           StringUtils.mid("abc", 4, 2)   = ""
           StringUtils.mid("abc", -2, 2)  = "ab"

      Parameters:
        `str` - the String to get the characters from, may be null
        `pos` - the position to start from, negative treated as zero
        `len` - the length of the required String
      Returns:
        the middle characters, `null` if null String input

    - #### substringBefore

          public static String substringBefore​(String str,
                                               String separator)

      Gets the substring before the first occurrence of a separator. The separator is not returned.

      A `null` string input will return `null`. An empty ("") string input will return the empty string. A `null` separator will return the input string.

      If nothing is found, the string input is returned.

           StringUtils.substringBefore(null, *)      = null
           StringUtils.substringBefore("", *)        = ""
           StringUtils.substringBefore("abc", "a")   = ""
           StringUtils.substringBefore("abcba", "b") = "a"
           StringUtils.substringBefore("abc", "c")   = "ab"
           StringUtils.substringBefore("abc", "d")   = "abc"
           StringUtils.substringBefore("abc", "")    = ""
           StringUtils.substringBefore("abc", null)  = "abc"

      Parameters:
        `str` - the String to get a substring from, may be null
        `separator` - the String to search for, may be null
      Returns:
        the substring before the first occurrence of the separator, `null` if null String input
      Since:
        2.0

    - #### substringAfter

          public static String substringAfter​(String str,
                                              String separator)

      Gets the substring after the first occurrence of a separator. The separator is not returned.

      A `null` string input will return `null`. An empty ("") string input will return the empty string. A `null` separator will return the empty string if the input string is not `null`.

      If nothing is found, the empty string is returned.

           StringUtils.substringAfter(null, *)      = null
           StringUtils.substringAfter("", *)        = ""
           StringUtils.substringAfter(*, null)      = ""
           StringUtils.substringAfter("abc", "a")   = "bc"
           StringUtils.substringAfter("abcba", "b") = "cba"
           StringUtils.substringAfter("abc", "c")   = ""
           StringUtils.substringAfter("abc", "d")   = ""
           StringUtils.substringAfter("abc", "")    = "abc"

      Parameters:
        `str` - the String to get a substring from, may be null
        `separator` - the String to search for, may be null
      Returns:
        the substring after the first occurrence of the separator, `null` if null String input
      Since:
        2.0

    - #### substringBeforeLast

          public static String substringBeforeLast​(String str,
                                                   String separator)

      Gets the substring before the last occurrence of a separator. The separator is not returned.

      A `null` string input will return `null`. An empty ("") string input will return the empty string. An empty or `null` separator will return the input string.

      If nothing is found, the string input is returned.

           StringUtils.substringBeforeLast(null, *)      = null
           StringUtils.substringBeforeLast("", *)        = ""
           StringUtils.substringBeforeLast("abcba", "b") = "abc"
           StringUtils.substringBeforeLast("abc", "c")   = "ab"
           StringUtils.substringBeforeLast("a", "a")     = ""
           StringUtils.substringBeforeLast("a", "z")     = "a"
           StringUtils.substringBeforeLast("a", null)    = "a"
           StringUtils.substringBeforeLast("a", "")      = "a"

      Parameters:
        `str` - the String to get a substring from, may be null
        `separator` - the String to search for, may be null
      Returns:
        the substring before the last occurrence of the separator, `null` if null String input
      Since:
        2.0

    - #### substringAfterLast

          public static String substringAfterLast​(String str,
                                                  String separator)

      Gets the substring after the last occurrence of a separator. The separator is not returned.

      A `null` string input will return `null`. An empty ("") string input will return the empty string. An empty or `null` separator will return the empty string if the input string is not `null`.

      If nothing is found, the empty string is returned.

           StringUtils.substringAfterLast(null, *)      = null
           StringUtils.substringAfterLast("", *)        = ""
           StringUtils.substringAfterLast(*, "")        = ""
           StringUtils.substringAfterLast(*, null)      = ""
           StringUtils.substringAfterLast("abc", "a")   = "bc"
           StringUtils.substringAfterLast("abcba", "b") = "a"
           StringUtils.substringAfterLast("abc", "c")   = ""
           StringUtils.substringAfterLast("a", "a")     = ""
           StringUtils.substringAfterLast("a", "z")     = ""

      Parameters:
        `str` - the String to get a substring from, may be null
        `separator` - the String to search for, may be null
      Returns:
        the substring after the last occurrence of the separator, `null` if null String input
      Since:
        2.0

    - #### substringBetween

          public static String substringBetween​(String str,
                                                String tag)

      Gets the String that is nested in between two instances of the same String.

      A `null` input String returns `null`. A `null` tag returns `null`.

           StringUtils.substringBetween(null, *)            = null
           StringUtils.substringBetween("", "")             = ""
           StringUtils.substringBetween("", "tag")          = null
           StringUtils.substringBetween("tagabctag", null)  = null
           StringUtils.substringBetween("tagabctag", "")    = ""
           StringUtils.substringBetween("tagabctag", "tag") = "abc"

      Parameters:
        `str` - the String containing the substring, may be null
        `tag` - the String before and after the substring, may be null
      Returns:
        the substring, `null` if no match
      Since:
        2.0

    - #### substringBetween

          public static String substringBetween​(String str,
                                                String open,
                                                String close)

      Gets the String that is nested in between two Strings. Only the first match is returned.

      A `null` input String returns `null`. A `null` open/close returns `null` (no match). An empty ("") open and close returns an empty string.

           StringUtils.substringBetween("wx[b]yz", "[", "]") = "b"
           StringUtils.substringBetween(null, *, *)          = null
           StringUtils.substringBetween(*, null, *)          = null
           StringUtils.substringBetween(*, *, null)          = null
           StringUtils.substringBetween("", "", "")          = ""
           StringUtils.substringBetween("", "", "]")         = null
           StringUtils.substringBetween("", "[", "]")        = null
           StringUtils.substringBetween("yabcz", "", "")     = ""
           StringUtils.substringBetween("yabcz", "y", "z")   = "abc"
           StringUtils.substringBetween("yabczyabcz", "y", "z")   = "abc"

      Parameters:
        `str` - the String containing the substring, may be null
        `open` - the String before the substring, may be null
        `close` - the String after the substring, may be null
      Returns:
        the substring, `null` if no match
      Since:
        2.0

    - #### substringsBetween

          public static String[] substringsBetween​(String str,
                                                   String open,
                                                   String close)

      Searches a String for substrings delimited by a start and end tag, returning all matching substrings in an array.

      A `null` input String returns `null`. A `null` open/close returns `null` (no match). An empty ("") open/close returns `null` (no match).

           StringUtils.substringsBetween("[a][b][c]", "[", "]") = ["a","b","c"]
           StringUtils.substringsBetween(null, *, *)            = null
           StringUtils.substringsBetween(*, null, *)            = null
           StringUtils.substringsBetween(*, *, null)            = null
           StringUtils.substringsBetween("", "[", "]")          = []

      Parameters:
        `str` - the String containing the substrings, null returns null, empty returns empty
        `open` - the String identifying the start of the substring, empty returns null
        `close` - the String identifying the end of the substring, empty returns null
      Returns:
        a String Array of substrings, or `null` if no match
      Since:
        2.3

    - #### getNestedString

          public static String getNestedString​(String str,
                                               String tag)

      Deprecated.
      Use the better named `substringBetween(String, String)`. Method will be removed in Commons Lang 3.0.

      Gets the String that is nested in between two instances of the same String.

      A `null` input String returns `null`. A `null` tag returns `null`.

           StringUtils.getNestedString(null, *)            = null
           StringUtils.getNestedString("", "")             = ""
           StringUtils.getNestedString("", "tag")          = null
           StringUtils.getNestedString("tagabctag", null)  = null
           StringUtils.getNestedString("tagabctag", "")    = ""
           StringUtils.getNestedString("tagabctag", "tag") = "abc"

      Parameters:
        `str` - the String containing nested-string, may be null
        `tag` - the String before and after nested-string, may be null
      Returns:
        the nested String, `null` if no match

    - #### getNestedString

          public static String getNestedString​(String str,
                                               String open,
                                               String close)

      Deprecated.
      Use the better named `substringBetween(String, String, String)`. Method will be removed in Commons Lang 3.0.

      Gets the String that is nested in between two Strings. Only the first match is returned.

      A `null` input String returns `null`. A `null` open/close returns `null` (no match). An empty ("") open/close returns an empty string.

           StringUtils.getNestedString(null, *, *)          = null
           StringUtils.getNestedString("", "", "")          = ""
           StringUtils.getNestedString("", "", "tag")       = null
           StringUtils.getNestedString("", "tag", "tag")    = null
           StringUtils.getNestedString("yabcz", null, null) = null
           StringUtils.getNestedString("yabcz", "", "")     = ""
           StringUtils.getNestedString("yabcz", "y", "z")   = "abc"
           StringUtils.getNestedString("yabczyabcz", "y", "z")   = "abc"

      Parameters:
        `str` - the String containing nested-string, may be null
        `open` - the String before nested-string, may be null
        `close` - the String after nested-string, may be null
      Returns:
        the nested String, `null` if no match

    - #### split

          public static String[] split​(String str)

      Splits the provided text into an array, using whitespace as the separator. Whitespace is defined by `Character.isWhitespace(char)`.

      The separator is not included in the returned String array. Adjacent separators are treated as one separator. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`.

           StringUtils.split(null)       = null
           StringUtils.split("")         = []
           StringUtils.split("abc def")  = ["abc", "def"]
           StringUtils.split("abc  def") = ["abc", "def"]
           StringUtils.split(" abc ")    = ["abc"]

      Parameters:
        `str` - the String to parse, may be null
      Returns:
        an array of parsed Strings, `null` if null String input

    - #### split

          public static String[] split​(String str,
                                       char separatorChar)

      Splits the provided text into an array, separator specified. This is an alternative to using StringTokenizer.

      The separator is not included in the returned String array. Adjacent separators are treated as one separator. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`.

           StringUtils.split(null, *)         = null
           StringUtils.split("", *)           = []
           StringUtils.split("a.b.c", '.')    = ["a", "b", "c"]
           StringUtils.split("a..b.c", '.')   = ["a", "b", "c"]
           StringUtils.split("a:b:c", '.')    = ["a:b:c"]
           StringUtils.split("a b c", ' ')    = ["a", "b", "c"]

      Parameters:
        `str` - the String to parse, may be null
        `separatorChar` - the character used as the delimiter
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.0

    - #### split

          public static String[] split​(String str,
                                       String separatorChars)

      Splits the provided text into an array, separators specified. This is an alternative to using StringTokenizer.

      The separator is not included in the returned String array. Adjacent separators are treated as one separator. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`. A `null` separatorChars splits on whitespace.

           StringUtils.split(null, *)         = null
           StringUtils.split("", *)           = []
           StringUtils.split("abc def", null) = ["abc", "def"]
           StringUtils.split("abc def", " ")  = ["abc", "def"]
           StringUtils.split("abc  def", " ") = ["abc", "def"]
           StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separatorChars` - the characters used as the delimiters, `null` splits on whitespace
      Returns:
        an array of parsed Strings, `null` if null String input

    - #### split

          public static String[] split​(String str,
                                       String separatorChars,
                                       int max)

      Splits the provided text into an array with a maximum length, separators specified.

      The separator is not included in the returned String array. Adjacent separators are treated as one separator.

      A `null` input String returns `null`. A `null` separatorChars splits on whitespace.

      If more than `max` delimited substrings are found, the last returned string includes all characters after the first `max - 1` returned strings (including separator characters).

           StringUtils.split(null, *, *)            = null
           StringUtils.split("", *, *)              = []
           StringUtils.split("ab de fg", null, 0)   = ["ab", "cd", "ef"]
           StringUtils.split("ab   de fg", null, 0) = ["ab", "cd", "ef"]
           StringUtils.split("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
           StringUtils.split("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separatorChars` - the characters used as the delimiters, `null` splits on whitespace
        `max` - the maximum number of elements to include in the array. A zero or negative value implies no limit
      Returns:
        an array of parsed Strings, `null` if null String input

    - #### splitByWholeSeparator

          public static String[] splitByWholeSeparator​(String str,
                                                       String separator)

      Splits the provided text into an array, separator string specified.

      The separator(s) will not be included in the returned String array. Adjacent separators are treated as one separator.

      A `null` input String returns `null`. A `null` separator splits on whitespace.

           StringUtils.splitByWholeSeparator(null, *)               = null
           StringUtils.splitByWholeSeparator("", *)                 = []
           StringUtils.splitByWholeSeparator("ab de fg", null)      = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparator("ab   de fg", null)    = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparator("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
           StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separator` - String containing the String to be used as a delimiter, `null` splits on whitespace
      Returns:
        an array of parsed Strings, `null` if null String was input

    - #### splitByWholeSeparator

          public static String[] splitByWholeSeparator​(String str,
                                                       String separator,
                                                       int max)

      Splits the provided text into an array, separator string specified. Returns a maximum of `max` substrings.

      The separator(s) will not be included in the returned String array. Adjacent separators are treated as one separator.

      A `null` input String returns `null`. A `null` separator splits on whitespace.

           StringUtils.splitByWholeSeparator(null, *, *)               = null
           StringUtils.splitByWholeSeparator("", *, *)                 = []
           StringUtils.splitByWholeSeparator("ab de fg", null, 0)      = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparator("ab   de fg", null, 0)    = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparator("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
           StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
           StringUtils.splitByWholeSeparator("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separator` - String containing the String to be used as a delimiter, `null` splits on whitespace
        `max` - the maximum number of elements to include in the returned array. A zero or negative value implies no limit.
      Returns:
        an array of parsed Strings, `null` if null String was input

    - #### splitByWholeSeparatorPreserveAllTokens

          public static String[] splitByWholeSeparatorPreserveAllTokens​(String str,
                                                                        String separator)

      Splits the provided text into an array, separator string specified.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`. A `null` separator splits on whitespace.

           StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *)               = null
           StringUtils.splitByWholeSeparatorPreserveAllTokens("", *)                 = []
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null)      = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null)    = ["ab", "", "", "de", "fg"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":")       = ["ab", "cd", "ef"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-") = ["ab", "cd", "ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separator` - String containing the String to be used as a delimiter, `null` splits on whitespace
      Returns:
        an array of parsed Strings, `null` if null String was input
      Since:
        2.4

    - #### splitByWholeSeparatorPreserveAllTokens

          public static String[] splitByWholeSeparatorPreserveAllTokens​(String str,
                                                                        String separator,
                                                                        int max)

      Splits the provided text into an array, separator string specified. Returns a maximum of `max` substrings.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`. A `null` separator splits on whitespace.

           StringUtils.splitByWholeSeparatorPreserveAllTokens(null, *, *)               = null
           StringUtils.splitByWholeSeparatorPreserveAllTokens("", *, *)                 = []
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab de fg", null, 0)      = ["ab", "de", "fg"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab   de fg", null, 0)    = ["ab", "", "", "de", "fg"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab:cd:ef", ":", 2)       = ["ab", "cd:ef"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 5) = ["ab", "cd", "ef"]
           StringUtils.splitByWholeSeparatorPreserveAllTokens("ab-!-cd-!-ef", "-!-", 2) = ["ab", "cd-!-ef"]

      Parameters:
        `str` - the String to parse, may be null
        `separator` - String containing the String to be used as a delimiter, `null` splits on whitespace
        `max` - the maximum number of elements to include in the returned array. A zero or negative value implies no limit.
      Returns:
        an array of parsed Strings, `null` if null String was input
      Since:
        2.4

    - #### splitPreserveAllTokens

          public static String[] splitPreserveAllTokens​(String str)

      Splits the provided text into an array, using whitespace as the separator, preserving all tokens, including empty tokens created by adjacent separators. This is an alternative to using StringTokenizer. Whitespace is defined by `Character.isWhitespace(char)`.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`.

           StringUtils.splitPreserveAllTokens(null)       = null
           StringUtils.splitPreserveAllTokens("")         = []
           StringUtils.splitPreserveAllTokens("abc def")  = ["abc", "def"]
           StringUtils.splitPreserveAllTokens("abc  def") = ["abc", "", "def"]
           StringUtils.splitPreserveAllTokens(" abc ")    = ["", "abc", ""]

      Parameters:
        `str` - the String to parse, may be `null`
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.1

    - #### splitPreserveAllTokens

          public static String[] splitPreserveAllTokens​(String str,
                                                        char separatorChar)

      Splits the provided text into an array, separator specified, preserving all tokens, including empty tokens created by adjacent separators. This is an alternative to using StringTokenizer.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`.

           StringUtils.splitPreserveAllTokens(null, *)         = null
           StringUtils.splitPreserveAllTokens("", *)           = []
           StringUtils.splitPreserveAllTokens("a.b.c", '.')    = ["a", "b", "c"]
           StringUtils.splitPreserveAllTokens("a..b.c", '.')   = ["a", "", "b", "c"]
           StringUtils.splitPreserveAllTokens("a:b:c", '.')    = ["a:b:c"]
           StringUtils.splitPreserveAllTokens("a\tb\nc", null) = ["a", "b", "c"]
           StringUtils.splitPreserveAllTokens("a b c", ' ')    = ["a", "b", "c"]
           StringUtils.splitPreserveAllTokens("a b c ", ' ')   = ["a", "b", "c", ""]
           StringUtils.splitPreserveAllTokens("a b c  ", ' ')   = ["a", "b", "c", "", ""]
           StringUtils.splitPreserveAllTokens(" a b c", ' ')   = ["", a", "b", "c"]
           StringUtils.splitPreserveAllTokens("  a b c", ' ')  = ["", "", a", "b", "c"]
           StringUtils.splitPreserveAllTokens(" a b c ", ' ')  = ["", a", "b", "c", ""]

      Parameters:
        `str` - the String to parse, may be `null`
        `separatorChar` - the character used as the delimiter, `null` splits on whitespace
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.1

    - #### splitPreserveAllTokens

          public static String[] splitPreserveAllTokens​(String str,
                                                        String separatorChars)

      Splits the provided text into an array, separators specified, preserving all tokens, including empty tokens created by adjacent separators. This is an alternative to using StringTokenizer.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. For more control over the split use the StrTokenizer class.

      A `null` input String returns `null`. A `null` separatorChars splits on whitespace.

           StringUtils.splitPreserveAllTokens(null, *)           = null
           StringUtils.splitPreserveAllTokens("", *)             = []
           StringUtils.splitPreserveAllTokens("abc def", null)   = ["abc", "def"]
           StringUtils.splitPreserveAllTokens("abc def", " ")    = ["abc", "def"]
           StringUtils.splitPreserveAllTokens("abc  def", " ")   = ["abc", "", def"]
           StringUtils.splitPreserveAllTokens("ab:cd:ef", ":")   = ["ab", "cd", "ef"]
           StringUtils.splitPreserveAllTokens("ab:cd:ef:", ":")  = ["ab", "cd", "ef", ""]
           StringUtils.splitPreserveAllTokens("ab:cd:ef::", ":") = ["ab", "cd", "ef", "", ""]
           StringUtils.splitPreserveAllTokens("ab::cd:ef", ":")  = ["ab", "", cd", "ef"]
           StringUtils.splitPreserveAllTokens(":cd:ef", ":")     = ["", cd", "ef"]
           StringUtils.splitPreserveAllTokens("::cd:ef", ":")    = ["", "", cd", "ef"]
           StringUtils.splitPreserveAllTokens(":cd:ef:", ":")    = ["", cd", "ef", ""]

      Parameters:
        `str` - the String to parse, may be `null`
        `separatorChars` - the characters used as the delimiters, `null` splits on whitespace
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.1

    - #### splitPreserveAllTokens

          public static String[] splitPreserveAllTokens​(String str,
                                                        String separatorChars,
                                                        int max)

      Splits the provided text into an array with a maximum length, separators specified, preserving all tokens, including empty tokens created by adjacent separators.

      The separator is not included in the returned String array. Adjacent separators are treated as separators for empty tokens. Adjacent separators are treated as one separator.

      A `null` input String returns `null`. A `null` separatorChars splits on whitespace.

      If more than `max` delimited substrings are found, the last returned string includes all characters after the first `max - 1` returned strings (including separator characters).

           StringUtils.splitPreserveAllTokens(null, *, *)            = null
           StringUtils.splitPreserveAllTokens("", *, *)              = []
           StringUtils.splitPreserveAllTokens("ab de fg", null, 0)   = ["ab", "cd", "ef"]
           StringUtils.splitPreserveAllTokens("ab   de fg", null, 0) = ["ab", "cd", "ef"]
           StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 0)    = ["ab", "cd", "ef"]
           StringUtils.splitPreserveAllTokens("ab:cd:ef", ":", 2)    = ["ab", "cd:ef"]
           StringUtils.splitPreserveAllTokens("ab   de fg", null, 2) = ["ab", "  de fg"]
           StringUtils.splitPreserveAllTokens("ab   de fg", null, 3) = ["ab", "", " de fg"]
           StringUtils.splitPreserveAllTokens("ab   de fg", null, 4) = ["ab", "", "", "de fg"]

      Parameters:
        `str` - the String to parse, may be `null`
        `separatorChars` - the characters used as the delimiters, `null` splits on whitespace
        `max` - the maximum number of elements to include in the array. A zero or negative value implies no limit
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.1

    - #### splitByCharacterType

          public static String[] splitByCharacterType​(String str)

      Splits a String by Character type as returned by `java.lang.Character.getType(char)`. Groups of contiguous characters of the same type are returned as complete tokens.

           StringUtils.splitByCharacterType(null)         = null
           StringUtils.splitByCharacterType("")           = []
           StringUtils.splitByCharacterType("ab de fg")   = ["ab", " ", "de", " ", "fg"]
           StringUtils.splitByCharacterType("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
           StringUtils.splitByCharacterType("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
           StringUtils.splitByCharacterType("number5")    = ["number", "5"]
           StringUtils.splitByCharacterType("fooBar")     = ["foo", "B", "ar"]
           StringUtils.splitByCharacterType("foo200Bar")  = ["foo", "200", "B", "ar"]
           StringUtils.splitByCharacterType("ASFRules")   = ["ASFR", "ules"]

      Parameters:
        `str` - the String to split, may be `null`
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.4

    - #### splitByCharacterTypeCamelCase

          public static String[] splitByCharacterTypeCamelCase​(String str)

      Splits a String by Character type as returned by `java.lang.Character.getType(char)`. Groups of contiguous characters of the same type are returned as complete tokens, with the following exception: the character of type `Character.UPPERCASE_LETTER`, if any, immediately preceding a token of type `Character.LOWERCASE_LETTER` will belong to the following token rather than to the preceding, if any, `Character.UPPERCASE_LETTER` token.

           StringUtils.splitByCharacterTypeCamelCase(null)         = null
           StringUtils.splitByCharacterTypeCamelCase("")           = []
           StringUtils.splitByCharacterTypeCamelCase("ab de fg")   = ["ab", " ", "de", " ", "fg"]
           StringUtils.splitByCharacterTypeCamelCase("ab   de fg") = ["ab", "   ", "de", " ", "fg"]
           StringUtils.splitByCharacterTypeCamelCase("ab:cd:ef")   = ["ab", ":", "cd", ":", "ef"]
           StringUtils.splitByCharacterTypeCamelCase("number5")    = ["number", "5"]
           StringUtils.splitByCharacterTypeCamelCase("fooBar")     = ["foo", "Bar"]
           StringUtils.splitByCharacterTypeCamelCase("foo200Bar")  = ["foo", "200", "Bar"]
           StringUtils.splitByCharacterTypeCamelCase("ASFRules")   = ["ASF", "Rules"]

      Parameters:
        `str` - the String to split, may be `null`
      Returns:
        an array of parsed Strings, `null` if null String input
      Since:
        2.4

    - #### concatenate

          public static String concatenate​(Object[] array)

      Deprecated.
      Use the better named `join(Object[])` instead. Method will be removed in Commons Lang 3.0.

      Joins the provided elements into a single String.

      No separator is added to the joined String. Null objects or empty string elements are represented by empty strings.

           StringUtils.concatenate(null)            = null
           StringUtils.concatenate([])              = ""
           StringUtils.concatenate([null])          = ""
           StringUtils.concatenate(["a", "b", "c"]) = "abc"
           StringUtils.concatenate([null, "", "a"]) = "a"

      Parameters:
        `array` - the array of values to concatenate, may be null
      Returns:
        the concatenated String, `null` if null array input

    - #### join

          public static String join​(Object[] array)

      Joins the elements of the provided array into a single String containing the provided list of elements.

      No separator is added to the joined String. Null objects or empty strings within the array are represented by empty strings.

           StringUtils.join(null)            = null
           StringUtils.join([])              = ""
           StringUtils.join([null])          = ""
           StringUtils.join(["a", "b", "c"]) = "abc"
           StringUtils.join([null, "", "a"]) = "a"

      Parameters:
        `array` - the array of values to join together, may be null
      Returns:
        the joined String, `null` if null array input
      Since:
        2.0

    - #### join

          public static String join​(Object[] array,
                                    char separator)

      Joins the elements of the provided array into a single String containing the provided list of elements.

      No delimiter is added before or after the list. Null objects or empty strings within the array are represented by empty strings.

           StringUtils.join(null, *)               = null
           StringUtils.join([], *)                 = ""
           StringUtils.join([null], *)             = ""
           StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
           StringUtils.join(["a", "b", "c"], null) = "abc"
           StringUtils.join([null, "", "a"], ';')  = ";;a"

      Parameters:
        `array` - the array of values to join together, may be null
        `separator` - the separator character to use
      Returns:
        the joined String, `null` if null array input
      Since:
        2.0

    - #### join

          public static String join​(Object[] array,
                                    char separator,
                                    int startIndex,
                                    int endIndex)

      Joins the elements of the provided array into a single String containing the provided list of elements.

      No delimiter is added before or after the list. Null objects or empty strings within the array are represented by empty strings.

           StringUtils.join(null, *)               = null
           StringUtils.join([], *)                 = ""
           StringUtils.join([null], *)             = ""
           StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
           StringUtils.join(["a", "b", "c"], null) = "abc"
           StringUtils.join([null, "", "a"], ';')  = ";;a"

      Parameters:
        `array` - the array of values to join together, may be null
        `separator` - the separator character to use
        `startIndex` - the first index to start joining from. It is an error to pass in an end index past the end of the array
        `endIndex` - the index to stop joining from (exclusive). It is an error to pass in an end index past the end of the array
      Returns:
        the joined String, `null` if null array input
      Since:
        2.0

    - #### join

          public static String join​(Object[] array,
                                    String separator)

      Joins the elements of the provided array into a single String containing the provided list of elements.

      No delimiter is added before or after the list. A `null` separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.

           StringUtils.join(null, *)                = null
           StringUtils.join([], *)                  = ""
           StringUtils.join([null], *)              = ""
           StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
           StringUtils.join(["a", "b", "c"], null)  = "abc"
           StringUtils.join(["a", "b", "c"], "")    = "abc"
           StringUtils.join([null, "", "a"], ',')   = ",,a"

      Parameters:
        `array` - the array of values to join together, may be null
        `separator` - the separator character to use, null treated as ""
      Returns:
        the joined String, `null` if null array input

    - #### join

          public static String join​(Object[] array,
                                    String separator,
                                    int startIndex,
                                    int endIndex)

      Joins the elements of the provided array into a single String containing the provided list of elements.

      No delimiter is added before or after the list. A `null` separator is the same as an empty String (""). Null objects or empty strings within the array are represented by empty strings.

           StringUtils.join(null, *)                = null
           StringUtils.join([], *)                  = ""
           StringUtils.join([null], *)              = ""
           StringUtils.join(["a", "b", "c"], "--")  = "a--b--c"
           StringUtils.join(["a", "b", "c"], null)  = "abc"
           StringUtils.join(["a", "b", "c"], "")    = "abc"
           StringUtils.join([null, "", "a"], ',')   = ",,a"

      Parameters:
        `array` - the array of values to join together, may be null
        `separator` - the separator character to use, null treated as ""
        `startIndex` - the first index to start joining from. It is an error to pass in an end index past the end of the array
        `endIndex` - the index to stop joining from (exclusive). It is an error to pass in an end index past the end of the array
      Returns:
        the joined String, `null` if null array input

    - #### join

          public static String join​(Iterator iterator,
                                    char separator)

      Joins the elements of the provided `Iterator` into a single String containing the provided elements.

      No delimiter is added before or after the list. Null objects or empty strings within the iteration are represented by empty strings.

      See the examples here: `join(Object[],char)`.

      Parameters:
        `iterator` - the `Iterator` of values to join together, may be null
        `separator` - the separator character to use
      Returns:
        the joined String, `null` if null iterator input
      Since:
        2.0

    - #### join

          public static String join​(Iterator iterator,
                                    String separator)

      Joins the elements of the provided `Iterator` into a single String containing the provided elements.

      No delimiter is added before or after the list. A `null` separator is the same as an empty String ("").

      See the examples here: `join(Object[],String)`.

      Parameters:
        `iterator` - the `Iterator` of values to join together, may be null
        `separator` - the separator character to use, null treated as ""
      Returns:
        the joined String, `null` if null iterator input

    - #### join

          public static String join​(Collection collection,
                                    char separator)

      Joins the elements of the provided `Collection` into a single String containing the provided elements.

      No delimiter is added before or after the list. Null objects or empty strings within the iteration are represented by empty strings.

      See the examples here: `join(Object[],char)`.

      Parameters:
        `collection` - the `Collection` of values to join together, may be null
        `separator` - the separator character to use
      Returns:
        the joined String, `null` if null iterator input
      Since:
        2.3

    - #### join

          public static String join​(Collection collection,
                                    String separator)

      Joins the elements of the provided `Collection` into a single String containing the provided elements.

      No delimiter is added before or after the list. A `null` separator is the same as an empty String ("").

      See the examples here: `join(Object[],String)`.

      Parameters:
        `collection` - the `Collection` of values to join together, may be null
        `separator` - the separator character to use, null treated as ""
      Returns:
        the joined String, `null` if null iterator input
      Since:
        2.3

    - #### deleteSpaces

          public static String deleteSpaces​(String str)

      Deprecated.
      Use the better localized `deleteWhitespace(String)`. Method will be removed in Commons Lang 3.0.

      Deletes all 'space' characters from a String as defined by `Character.isSpace(char)`.

      This is the only StringUtils method that uses the `isSpace` definition. You are advised to use `deleteWhitespace(String)` instead as whitespace is much better localized.

           StringUtils.deleteSpaces(null)           = null
           StringUtils.deleteSpaces("")             = ""
           StringUtils.deleteSpaces("abc")          = "abc"
           StringUtils.deleteSpaces(" \t  abc \n ") = "abc"
           StringUtils.deleteSpaces("ab  c")        = "abc"
           StringUtils.deleteSpaces("a\nb\tc     ") = "abc"

      Spaces are defined as `{' ', '\t', '\r', '\n', '\b'}` in line with the deprecated `isSpace` method.

      Parameters:
        `str` - the String to delete spaces from, may be null
      Returns:
        the String without 'spaces', `null` if null String input

    - #### deleteWhitespace

          public static String deleteWhitespace​(String str)

      Deletes all whitespaces from a String as defined by `Character.isWhitespace(char)`.

           StringUtils.deleteWhitespace(null)         = null
           StringUtils.deleteWhitespace("")           = ""
           StringUtils.deleteWhitespace("abc")        = "abc"
           StringUtils.deleteWhitespace("   ab  c  ") = "abc"

      Parameters:
        `str` - the String to delete whitespace from, may be null
      Returns:
        the String without whitespaces, `null` if null String input

    - #### removeStart

          public static String removeStart​(String str,
                                           String remove)

      Removes a substring only if it is at the begining of a source string, otherwise returns the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string. A `null` search string will return the source string.

           StringUtils.removeStart(null, *)      = null
           StringUtils.removeStart("", *)        = ""
           StringUtils.removeStart(*, null)      = *
           StringUtils.removeStart("www.domain.com", "www.")   = "domain.com"
           StringUtils.removeStart("domain.com", "www.")       = "domain.com"
           StringUtils.removeStart("www.domain.com", "domain") = "www.domain.com"
           StringUtils.removeStart("abc", "")    = "abc"

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the String to search for and remove, may be null
      Returns:
        the substring with the string removed if found, `null` if null String input
      Since:
        2.1

    - #### removeStartIgnoreCase

          public static String removeStartIgnoreCase​(String str,
                                                     String remove)

      Case insensitive removal of a substring if it is at the begining of a source string, otherwise returns the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string. A `null` search string will return the source string.

           StringUtils.removeStartIgnoreCase(null, *)      = null
           StringUtils.removeStartIgnoreCase("", *)        = ""
           StringUtils.removeStartIgnoreCase(*, null)      = *
           StringUtils.removeStartIgnoreCase("www.domain.com", "www.")   = "domain.com"
           StringUtils.removeStartIgnoreCase("www.domain.com", "WWW.")   = "domain.com"
           StringUtils.removeStartIgnoreCase("domain.com", "www.")       = "domain.com"
           StringUtils.removeStartIgnoreCase("www.domain.com", "domain") = "www.domain.com"
           StringUtils.removeStartIgnoreCase("abc", "")    = "abc"

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the String to search for (case insensitive) and remove, may be null
      Returns:
        the substring with the string removed if found, `null` if null String input
      Since:
        2.4

    - #### removeEnd

          public static String removeEnd​(String str,
                                         String remove)

      Removes a substring only if it is at the end of a source string, otherwise returns the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string. A `null` search string will return the source string.

           StringUtils.removeEnd(null, *)      = null
           StringUtils.removeEnd("", *)        = ""
           StringUtils.removeEnd(*, null)      = *
           StringUtils.removeEnd("www.domain.com", ".com.")  = "www.domain.com"
           StringUtils.removeEnd("www.domain.com", ".com")   = "www.domain"
           StringUtils.removeEnd("www.domain.com", "domain") = "www.domain.com"
           StringUtils.removeEnd("abc", "")    = "abc"

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the String to search for and remove, may be null
      Returns:
        the substring with the string removed if found, `null` if null String input
      Since:
        2.1

    - #### removeEndIgnoreCase

          public static String removeEndIgnoreCase​(String str,
                                                   String remove)

      Case insensitive removal of a substring if it is at the end of a source string, otherwise returns the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string. A `null` search string will return the source string.

           StringUtils.removeEndIgnoreCase(null, *)      = null
           StringUtils.removeEndIgnoreCase("", *)        = ""
           StringUtils.removeEndIgnoreCase(*, null)      = *
           StringUtils.removeEndIgnoreCase("www.domain.com", ".com.")  = "www.domain.com"
           StringUtils.removeEndIgnoreCase("www.domain.com", ".com")   = "www.domain"
           StringUtils.removeEndIgnoreCase("www.domain.com", "domain") = "www.domain.com"
           StringUtils.removeEndIgnoreCase("abc", "")    = "abc"
           StringUtils.removeEndIgnoreCase("www.domain.com", ".COM") = "www.domain")
           StringUtils.removeEndIgnoreCase("www.domain.COM", ".com") = "www.domain")

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the String to search for (case insensitive) and remove, may be null
      Returns:
        the substring with the string removed if found, `null` if null String input
      Since:
        2.4

    - #### remove

          public static String remove​(String str,
                                      String remove)

      Removes all occurrences of a substring from within the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string. A `null` remove string will return the source string. An empty ("") remove string will return the source string.

           StringUtils.remove(null, *)        = null
           StringUtils.remove("", *)          = ""
           StringUtils.remove(*, null)        = *
           StringUtils.remove(*, "")          = *
           StringUtils.remove("queued", "ue") = "qd"
           StringUtils.remove("queued", "zz") = "queued"

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the String to search for and remove, may be null
      Returns:
        the substring with the string removed if found, `null` if null String input
      Since:
        2.1

    - #### remove

          public static String remove​(String str,
                                      char remove)

      Removes all occurrences of a character from within the source string.

      A `null` source string will return `null`. An empty ("") source string will return the empty string.

           StringUtils.remove(null, *)       = null
           StringUtils.remove("", *)         = ""
           StringUtils.remove("queued", 'u') = "qeed"
           StringUtils.remove("queued", 'z') = "queued"

      Parameters:
        `str` - the source String to search, may be null
        `remove` - the char to search for and remove, may be null
      Returns:
        the substring with the char removed if found, `null` if null String input
      Since:
        2.1

    - #### replaceOnce

          public static String replaceOnce​(String text,
                                           String searchString,
                                           String replacement)

      Replaces a String with another String inside a larger String, once.

      A `null` reference passed to this method is a no-op.

           StringUtils.replaceOnce(null, *, *)        = null
           StringUtils.replaceOnce("", *, *)          = ""
           StringUtils.replaceOnce("any", null, *)    = "any"
           StringUtils.replaceOnce("any", *, null)    = "any"
           StringUtils.replaceOnce("any", "", *)      = "any"
           StringUtils.replaceOnce("aba", "a", null)  = "aba"
           StringUtils.replaceOnce("aba", "a", "")    = "ba"
           StringUtils.replaceOnce("aba", "a", "z")   = "zba"

      Parameters:
        `text` - text to search and replace in, may be null
        `searchString` - the String to search for, may be null
        `replacement` - the String to replace with, may be null
      Returns:
        the text with any replacements processed, `null` if null String input
      See Also:
        `replace(String text, String searchString, String replacement, int max)`

    - #### replace

          public static String replace​(String text,
                                       String searchString,
                                       String replacement)

      Replaces all occurrences of a String within another String.

      A `null` reference passed to this method is a no-op.

           StringUtils.replace(null, *, *)        = null
           StringUtils.replace("", *, *)          = ""
           StringUtils.replace("any", null, *)    = "any"
           StringUtils.replace("any", *, null)    = "any"
           StringUtils.replace("any", "", *)      = "any"
           StringUtils.replace("aba", "a", null)  = "aba"
           StringUtils.replace("aba", "a", "")    = "b"
           StringUtils.replace("aba", "a", "z")   = "zbz"

      Parameters:
        `text` - text to search and replace in, may be null
        `searchString` - the String to search for, may be null
        `replacement` - the String to replace it with, may be null
      Returns:
        the text with any replacements processed, `null` if null String input
      See Also:
        `replace(String text, String searchString, String replacement, int max)`

    - #### replace

          public static String replace​(String text,
                                       String searchString,
                                       String replacement,
                                       int max)

      Replaces a String with another String inside a larger String, for the first `max` values of the search String.

      A `null` reference passed to this method is a no-op.

           StringUtils.replace(null, *, *, *)         = null
           StringUtils.replace("", *, *, *)           = ""
           StringUtils.replace("any", null, *, *)     = "any"
           StringUtils.replace("any", *, null, *)     = "any"
           StringUtils.replace("any", "", *, *)       = "any"
           StringUtils.replace("any", *, *, 0)        = "any"
           StringUtils.replace("abaa", "a", null, -1) = "abaa"
           StringUtils.replace("abaa", "a", "", -1)   = "b"
           StringUtils.replace("abaa", "a", "z", 0)   = "abaa"
           StringUtils.replace("abaa", "a", "z", 1)   = "zbaa"
           StringUtils.replace("abaa", "a", "z", 2)   = "zbza"
           StringUtils.replace("abaa", "a", "z", -1)  = "zbzz"

      Parameters:
        `text` - text to search and replace in, may be null
        `searchString` - the String to search for, may be null
        `replacement` - the String to replace it with, may be null
        `max` - maximum number of values to replace, or `-1` if no maximum
      Returns:
        the text with any replacements processed, `null` if null String input

    - #### replaceEach

          public static String replaceEach​(String text,
                                           String[] searchList,
                                           String[] replacementList)

      Replaces all occurrences of Strings within another String.

      A `null` reference passed to this method is a no-op, or if any "search string" or "string to replace" is null, that replace will be ignored. This will not repeat. For repeating replaces, call the overloaded method.

            StringUtils.replaceEach(null, *, *)        = null
            StringUtils.replaceEach("", *, *)          = ""
            StringUtils.replaceEach("aba", null, null) = "aba"
            StringUtils.replaceEach("aba", new String[0], null) = "aba"
            StringUtils.replaceEach("aba", null, new String[0]) = "aba"
            StringUtils.replaceEach("aba", new String[]{"a"}, null)  = "aba"
            StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""})  = "b"
            StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"})  = "aba"
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"})  = "wcte"
            (example of how it does not repeat)
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"})  = "dcte"

      Parameters:
        `text` - text to search and replace in, no-op if null
        `searchList` - the Strings to search for, no-op if null
        `replacementList` - the Strings to replace them with, no-op if null
      Returns:
        the text with any replacements processed, `null` if null String input
      Throws:
        `IndexOutOfBoundsException` - if the lengths of the arrays are not the same (null is ok, and/or size 0)
      Since:
        2.4

    - #### replaceEachRepeatedly

          public static String replaceEachRepeatedly​(String text,
                                                     String[] searchList,
                                                     String[] replacementList)

      Replaces all occurrences of Strings within another String.

      A `null` reference passed to this method is a no-op, or if any "search string" or "string to replace" is null, that replace will be ignored. This will not repeat. For repeating replaces, call the overloaded method.

            StringUtils.replaceEach(null, *, *, *) = null
            StringUtils.replaceEach("", *, *, *) = ""
            StringUtils.replaceEach("aba", null, null, *) = "aba"
            StringUtils.replaceEach("aba", new String[0], null, *) = "aba"
            StringUtils.replaceEach("aba", null, new String[0], *) = "aba"
            StringUtils.replaceEach("aba", new String[]{"a"}, null, *) = "aba"
            StringUtils.replaceEach("aba", new String[]{"a"}, new String[]{""}, *) = "b"
            StringUtils.replaceEach("aba", new String[]{null}, new String[]{"a"}, *) = "aba"
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"w", "t"}, *) = "wcte"
            (example of how it repeats)
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, false) = "dcte"
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "t"}, true) = "tcte"
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}, true) = IllegalArgumentException
            StringUtils.replaceEach("abcde", new String[]{"ab", "d"}, new String[]{"d", "ab"}, false) = "dcabe"

      Parameters:
        `text` - text to search and replace in, no-op if null
        `searchList` - the Strings to search for, no-op if null
        `replacementList` - the Strings to replace them with, no-op if null
      Returns:
        the text with any replacements processed, `null` if null String input
      Throws:
        `IllegalArgumentException` - if the search is repeating and there is an endless loop due to outputs of one being inputs to another
        `IndexOutOfBoundsException` - if the lengths of the arrays are not the same (null is ok, and/or size 0)
      Since:
        2.4

    - #### replaceChars

          public static String replaceChars​(String str,
                                            char searchChar,
                                            char replaceChar)

      Replaces all occurrences of a character in a String with another. This is a null-safe version of `String.replace(char, char)`.

      A `null` string input returns `null`. An empty ("") string input returns an empty string.

           StringUtils.replaceChars(null, *, *)        = null
           StringUtils.replaceChars("", *, *)          = ""
           StringUtils.replaceChars("abcba", 'b', 'y') = "aycya"
           StringUtils.replaceChars("abcba", 'z', 'y') = "abcba"

      Parameters:
        `str` - String to replace characters in, may be null
        `searchChar` - the character to search for, may be null
        `replaceChar` - the character to replace, may be null
      Returns:
        modified String, `null` if null string input
      Since:
        2.0

    - #### replaceChars

          public static String replaceChars​(String str,
                                            String searchChars,
                                            String replaceChars)

      Replaces multiple characters in a String in one go. This method can also be used to delete characters.

      For example:
      `replaceChars("hello", "ho", "jy") = jelly`.

      A `null` string input returns `null`. An empty ("") string input returns an empty string. A null or empty set of search characters returns the input string.

      The length of the search characters should normally equal the length of the replace characters. If the search characters is longer, then the extra search characters are deleted. If the search characters is shorter, then the extra replace characters are ignored.

           StringUtils.replaceChars(null, *, *)           = null
           StringUtils.replaceChars("", *, *)             = ""
           StringUtils.replaceChars("abc", null, *)       = "abc"
           StringUtils.replaceChars("abc", "", *)         = "abc"
           StringUtils.replaceChars("abc", "b", null)     = "ac"
           StringUtils.replaceChars("abc", "b", "")       = "ac"
           StringUtils.replaceChars("abcba", "bc", "yz")  = "ayzya"
           StringUtils.replaceChars("abcba", "bc", "y")   = "ayya"
           StringUtils.replaceChars("abcba", "bc", "yzx") = "ayzya"

      Parameters:
        `str` - String to replace characters in, may be null
        `searchChars` - a set of characters to search for, may be null
        `replaceChars` - a set of characters to replace, may be null
      Returns:
        modified String, `null` if null string input
      Since:
        2.0

    - #### overlayString

          public static String overlayString​(String text,
                                             String overlay,
                                             int start,
                                             int end)

      Deprecated.
      Use better named `overlay(String, String, int, int)` instead. Method will be removed in Commons Lang 3.0.

      Overlays part of a String with another String.

           StringUtils.overlayString(null, *, *, *)           = NullPointerException
           StringUtils.overlayString(*, null, *, *)           = NullPointerException
           StringUtils.overlayString("", "abc", 0, 0)         = "abc"
           StringUtils.overlayString("abcdef", null, 2, 4)    = "abef"
           StringUtils.overlayString("abcdef", "", 2, 4)      = "abef"
           StringUtils.overlayString("abcdef", "zzzz", 2, 4)  = "abzzzzef"
           StringUtils.overlayString("abcdef", "zzzz", 4, 2)  = "abcdzzzzcdef"
           StringUtils.overlayString("abcdef", "zzzz", -1, 4) = IndexOutOfBoundsException
           StringUtils.overlayString("abcdef", "zzzz", 2, 8)  = IndexOutOfBoundsException

      Parameters:
        `text` - the String to do overlaying in, may be null
        `overlay` - the String to overlay, may be null
        `start` - the position to start overlaying at, must be valid
        `end` - the position to stop overlaying before, must be valid
      Returns:
        overlayed String, `null` if null String input
      Throws:
        `NullPointerException` - if text or overlay is null
        `IndexOutOfBoundsException` - if either position is invalid

    - #### overlay

          public static String overlay​(String str,
                                       String overlay,
                                       int start,
                                       int end)

      Overlays part of a String with another String.

      A `null` string input returns `null`. A negative index is treated as zero. An index greater than the string length is treated as the string length. The start index is always the smaller of the two indices.

           StringUtils.overlay(null, *, *, *)            = null
           StringUtils.overlay("", "abc", 0, 0)          = "abc"
           StringUtils.overlay("abcdef", null, 2, 4)     = "abef"
           StringUtils.overlay("abcdef", "", 2, 4)       = "abef"
           StringUtils.overlay("abcdef", "", 4, 2)       = "abef"
           StringUtils.overlay("abcdef", "zzzz", 2, 4)   = "abzzzzef"
           StringUtils.overlay("abcdef", "zzzz", 4, 2)   = "abzzzzef"
           StringUtils.overlay("abcdef", "zzzz", -1, 4)  = "zzzzef"
           StringUtils.overlay("abcdef", "zzzz", 2, 8)   = "abzzzz"
           StringUtils.overlay("abcdef", "zzzz", -2, -3) = "zzzzabcdef"
           StringUtils.overlay("abcdef", "zzzz", 8, 10)  = "abcdefzzzz"

      Parameters:
        `str` - the String to do overlaying in, may be null
        `overlay` - the String to overlay, may be null
        `start` - the position to start overlaying at
        `end` - the position to stop overlaying before
      Returns:
        overlayed String, `null` if null String input
      Since:
        2.0

    - #### chomp

          public static String chomp​(String str)

      Removes one newline from end of a String if it's there, otherwise leave it alone. A newline is "`\n`", "`\r`", or "`\r\n`".

      NOTE: This method changed in 2.0. It now more closely matches Perl chomp.

           StringUtils.chomp(null)          = null
           StringUtils.chomp("")            = ""
           StringUtils.chomp("abc \r")      = "abc "
           StringUtils.chomp("abc\n")       = "abc"
           StringUtils.chomp("abc\r\n")     = "abc"
           StringUtils.chomp("abc\r\n\r\n") = "abc\r\n"
           StringUtils.chomp("abc\n\r")     = "abc\n"
           StringUtils.chomp("abc\n\rabc")  = "abc\n\rabc"
           StringUtils.chomp("\r")          = ""
           StringUtils.chomp("\n")          = ""
           StringUtils.chomp("\r\n")        = ""

      Parameters:
        `str` - the String to chomp a newline from, may be null
      Returns:
        String without newline, `null` if null String input

    - #### chomp

          public static String chomp​(String str,
                                     String separator)

      Removes `separator` from the end of `str` if it's there, otherwise leave it alone.

      NOTE: This method changed in version 2.0. It now more closely matches Perl chomp. For the previous behavior, use `substringBeforeLast(String, String)`. This method uses `String.endsWith(String)`.

           StringUtils.chomp(null, *)         = null
           StringUtils.chomp("", *)           = ""
           StringUtils.chomp("foobar", "bar") = "foo"
           StringUtils.chomp("foobar", "baz") = "foobar"
           StringUtils.chomp("foo", "foo")    = ""
           StringUtils.chomp("foo ", "foo")   = "foo "
           StringUtils.chomp(" foo", "foo")   = " "
           StringUtils.chomp("foo", "foooo")  = "foo"
           StringUtils.chomp("foo", "")       = "foo"
           StringUtils.chomp("foo", null)     = "foo"

      Parameters:
        `str` - the String to chomp from, may be null
        `separator` - separator String, may be null
      Returns:
        String without trailing separator, `null` if null String input

    - #### chompLast

          public static String chompLast​(String str)

      Deprecated.
      Use `chomp(String)` instead. Method will be removed in Commons Lang 3.0.

      Remove any "\n" if and only if it is at the end of the supplied String.

      Parameters:
        `str` - the String to chomp from, must not be null
      Returns:
        String without chomped ending
      Throws:
        `NullPointerException` - if str is `null`

    - #### chompLast

          public static String chompLast​(String str,
                                         String sep)

      Deprecated.
      Use `chomp(String,String)` instead. Method will be removed in Commons Lang 3.0.

      Remove a value if and only if the String ends with that value.

      Parameters:
        `str` - the String to chomp from, must not be null
        `sep` - the String to chomp, must not be null
      Returns:
        String without chomped ending
      Throws:
        `NullPointerException` - if str or sep is `null`

    - #### getChomp

          public static String getChomp​(String str,
                                        String sep)

      Deprecated.
      Use `substringAfterLast(String, String)` instead (although this doesn't include the separator) Method will be removed in Commons Lang 3.0.

      Remove everything and return the last value of a supplied String, and everything after it from a String.

      Parameters:
        `str` - the String to chomp from, must not be null
        `sep` - the String to chomp, must not be null
      Returns:
        String chomped
      Throws:
        `NullPointerException` - if str or sep is `null`

    - #### prechomp

          public static String prechomp​(String str,
                                        String sep)

      Deprecated.
      Use `substringAfter(String,String)` instead. Method will be removed in Commons Lang 3.0.

      Remove the first value of a supplied String, and everything before it from a String.

      Parameters:
        `str` - the String to chomp from, must not be null
        `sep` - the String to chomp, must not be null
      Returns:
        String without chomped beginning
      Throws:
        `NullPointerException` - if str or sep is `null`

    - #### getPrechomp

          public static String getPrechomp​(String str,
                                           String sep)

      Deprecated.
      Use `substringBefore(String,String)` instead (although this doesn't include the separator). Method will be removed in Commons Lang 3.0.

      Remove and return everything before the first value of a supplied String from another String.

      Parameters:
        `str` - the String to chomp from, must not be null
        `sep` - the String to chomp, must not be null
      Returns:
        String prechomped
      Throws:
        `NullPointerException` - if str or sep is `null`

    - #### chop

          public static String chop​(String str)

      Remove the last character from a String.

      If the String ends in `\r\n`, then remove both of them.

           StringUtils.chop(null)          = null
           StringUtils.chop("")            = ""
           StringUtils.chop("abc \r")      = "abc "
           StringUtils.chop("abc\n")       = "abc"
           StringUtils.chop("abc\r\n")     = "abc"
           StringUtils.chop("abc")         = "ab"
           StringUtils.chop("abc\nabc")    = "abc\nab"
           StringUtils.chop("a")           = ""
           StringUtils.chop("\r")          = ""
           StringUtils.chop("\n")          = ""
           StringUtils.chop("\r\n")        = ""

      Parameters:
        `str` - the String to chop last character from, may be null
      Returns:
        String without last character, `null` if null String input

    - #### chopNewline

          public static String chopNewline​(String str)

      Deprecated.
      Use `chomp(String)` instead. Method will be removed in Commons Lang 3.0.

      Removes `\n` from end of a String if it's there. If a `\r` precedes it, then remove that too.

      Parameters:
        `str` - the String to chop a newline from, must not be null
      Returns:
        String without newline
      Throws:
        `NullPointerException` - if str is `null`

    - #### escape

          public static String escape​(String str)

      Deprecated.
      Use `StringEscapeUtils.escapeJava(String)` This method will be removed in Commons Lang 3.0

      Escapes any values it finds into their String form.

      So a tab becomes the characters `'\\'` and `'t'`.

      As of Lang 2.0, this calls `StringEscapeUtils.escapeJava(String)` behind the scenes.

      Parameters:
        `str` - String to escape values in
      Returns:
        String with escaped values
      Throws:
        `NullPointerException` - if str is `null`
      See Also:
        `StringEscapeUtils.escapeJava(java.lang.String)`

    - #### repeat

          public static String repeat​(String str,
                                      int repeat)

      Repeat a String `repeat` times to form a new String.

           StringUtils.repeat(null, 2) = null
           StringUtils.repeat("", 0)   = ""
           StringUtils.repeat("", 2)   = ""
           StringUtils.repeat("a", 3)  = "aaa"
           StringUtils.repeat("ab", 2) = "abab"
           StringUtils.repeat("a", -2) = ""

      Parameters:
        `str` - the String to repeat, may be null
        `repeat` - number of times to repeat str, negative treated as zero
      Returns:
        a new String consisting of the original String repeated, `null` if null String input

    - #### repeat

          public static String repeat​(String str,
                                      String separator,
                                      int repeat)

      Repeat a String `repeat` times to form a new String, with a String separator injected each time.

           StringUtils.repeat(null, null, 2) = null
           StringUtils.repeat(null, "x", 2)  = null
           StringUtils.repeat("", null, 0)   = ""
           StringUtils.repeat("", "", 2)     = ""
           StringUtils.repeat("", "x", 3)    = "xxx"
           StringUtils.repeat("?", ", ", 3)  = "?, ?, ?"

      Parameters:
        `str` - the String to repeat, may be null
        `separator` - the String to inject, may be null
        `repeat` - number of times to repeat str, negative treated as zero
      Returns:
        a new String consisting of the original String repeated, `null` if null String input
      Since:
        2.5

    - #### rightPad

          public static String rightPad​(String str,
                                        int size)

      Right pad a String with spaces (' ').

      The String is padded to the size of `size`.

           StringUtils.rightPad(null, *)   = null
           StringUtils.rightPad("", 3)     = "   "
           StringUtils.rightPad("bat", 3)  = "bat"
           StringUtils.rightPad("bat", 5)  = "bat  "
           StringUtils.rightPad("bat", 1)  = "bat"
           StringUtils.rightPad("bat", -1) = "bat"

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
      Returns:
        right padded String or original String if no padding is necessary, `null` if null String input

    - #### rightPad

          public static String rightPad​(String str,
                                        int size,
                                        char padChar)

      Right pad a String with a specified character.

      The String is padded to the size of `size`.

           StringUtils.rightPad(null, *, *)     = null
           StringUtils.rightPad("", 3, 'z')     = "zzz"
           StringUtils.rightPad("bat", 3, 'z')  = "bat"
           StringUtils.rightPad("bat", 5, 'z')  = "batzz"
           StringUtils.rightPad("bat", 1, 'z')  = "bat"
           StringUtils.rightPad("bat", -1, 'z') = "bat"

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
        `padChar` - the character to pad with
      Returns:
        right padded String or original String if no padding is necessary, `null` if null String input
      Since:
        2.0

    - #### rightPad

          public static String rightPad​(String str,
                                        int size,
                                        String padStr)

      Right pad a String with a specified String.

      The String is padded to the size of `size`.

           StringUtils.rightPad(null, *, *)      = null
           StringUtils.rightPad("", 3, "z")      = "zzz"
           StringUtils.rightPad("bat", 3, "yz")  = "bat"
           StringUtils.rightPad("bat", 5, "yz")  = "batyz"
           StringUtils.rightPad("bat", 8, "yz")  = "batyzyzy"
           StringUtils.rightPad("bat", 1, "yz")  = "bat"
           StringUtils.rightPad("bat", -1, "yz") = "bat"
           StringUtils.rightPad("bat", 5, null)  = "bat  "
           StringUtils.rightPad("bat", 5, "")    = "bat  "

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
        `padStr` - the String to pad with, null or empty treated as single space
      Returns:
        right padded String or original String if no padding is necessary, `null` if null String input

    - #### leftPad

          public static String leftPad​(String str,
                                       int size)

      Left pad a String with spaces (' ').

      The String is padded to the size of `size`.

           StringUtils.leftPad(null, *)   = null
           StringUtils.leftPad("", 3)     = "   "
           StringUtils.leftPad("bat", 3)  = "bat"
           StringUtils.leftPad("bat", 5)  = "  bat"
           StringUtils.leftPad("bat", 1)  = "bat"
           StringUtils.leftPad("bat", -1) = "bat"

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
      Returns:
        left padded String or original String if no padding is necessary, `null` if null String input

    - #### leftPad

          public static String leftPad​(String str,
                                       int size,
                                       char padChar)

      Left pad a String with a specified character.

      Pad to a size of `size`.

           StringUtils.leftPad(null, *, *)     = null
           StringUtils.leftPad("", 3, 'z')     = "zzz"
           StringUtils.leftPad("bat", 3, 'z')  = "bat"
           StringUtils.leftPad("bat", 5, 'z')  = "zzbat"
           StringUtils.leftPad("bat", 1, 'z')  = "bat"
           StringUtils.leftPad("bat", -1, 'z') = "bat"

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
        `padChar` - the character to pad with
      Returns:
        left padded String or original String if no padding is necessary, `null` if null String input
      Since:
        2.0

    - #### leftPad

          public static String leftPad​(String str,
                                       int size,
                                       String padStr)

      Left pad a String with a specified String.

      Pad to a size of `size`.

           StringUtils.leftPad(null, *, *)      = null
           StringUtils.leftPad("", 3, "z")      = "zzz"
           StringUtils.leftPad("bat", 3, "yz")  = "bat"
           StringUtils.leftPad("bat", 5, "yz")  = "yzbat"
           StringUtils.leftPad("bat", 8, "yz")  = "yzyzybat"
           StringUtils.leftPad("bat", 1, "yz")  = "bat"
           StringUtils.leftPad("bat", -1, "yz") = "bat"
           StringUtils.leftPad("bat", 5, null)  = "  bat"
           StringUtils.leftPad("bat", 5, "")    = "  bat"

      Parameters:
        `str` - the String to pad out, may be null
        `size` - the size to pad to
        `padStr` - the String to pad with, null or empty treated as single space
      Returns:
        left padded String or original String if no padding is necessary, `null` if null String input

    - #### length

          public static int length​(String str)

      Gets a String's length or `0` if the String is `null`.
      Parameters:
        `str` - a String or `null`
      Returns:
        String length or `0` if the String is `null`.
      Since:
        2.4

    - #### center

          public static String center​(String str,
                                      int size)

      Centers a String in a larger String of size `size` using the space character (' ').

      If the size is less than the String length, the String is returned. A `null` String returns `null`. A negative size is treated as zero.

      Equivalent to `center(str, size, " ")`.

           StringUtils.center(null, *)   = null
           StringUtils.center("", 4)     = "    "
           StringUtils.center("ab", -1)  = "ab"
           StringUtils.center("ab", 4)   = " ab "
           StringUtils.center("abcd", 2) = "abcd"
           StringUtils.center("a", 4)    = " a  "

      Parameters:
        `str` - the String to center, may be null
        `size` - the int size of new String, negative treated as zero
      Returns:
        centered String, `null` if null String input

    - #### center

          public static String center​(String str,
                                      int size,
                                      char padChar)

      Centers a String in a larger String of size `size`. Uses a supplied character as the value to pad the String with.

      If the size is less than the String length, the String is returned. A `null` String returns `null`. A negative size is treated as zero.

           StringUtils.center(null, *, *)     = null
           StringUtils.center("", 4, ' ')     = "    "
           StringUtils.center("ab", -1, ' ')  = "ab"
           StringUtils.center("ab", 4, ' ')   = " ab"
           StringUtils.center("abcd", 2, ' ') = "abcd"
           StringUtils.center("a", 4, ' ')    = " a  "
           StringUtils.center("a", 4, 'y')    = "yayy"

      Parameters:
        `str` - the String to center, may be null
        `size` - the int size of new String, negative treated as zero
        `padChar` - the character to pad the new String with
      Returns:
        centered String, `null` if null String input
      Since:
        2.0

    - #### center

          public static String center​(String str,
                                      int size,
                                      String padStr)

      Centers a String in a larger String of size `size`. Uses a supplied String as the value to pad the String with.

      If the size is less than the String length, the String is returned. A `null` String returns `null`. A negative size is treated as zero.

           StringUtils.center(null, *, *)     = null
           StringUtils.center("", 4, " ")     = "    "
           StringUtils.center("ab", -1, " ")  = "ab"
           StringUtils.center("ab", 4, " ")   = " ab"
           StringUtils.center("abcd", 2, " ") = "abcd"
           StringUtils.center("a", 4, " ")    = " a  "
           StringUtils.center("a", 4, "yz")   = "yayz"
           StringUtils.center("abc", 7, null) = "  abc  "
           StringUtils.center("abc", 7, "")   = "  abc  "

      Parameters:
        `str` - the String to center, may be null
        `size` - the int size of new String, negative treated as zero
        `padStr` - the String to pad the new String with, must not be null or empty
      Returns:
        centered String, `null` if null String input
      Throws:
        `IllegalArgumentException` - if padStr is `null` or empty

    - #### upperCase

          public static String upperCase​(String str)

      Converts a String to upper case as per `String.toUpperCase()`.

      A `null` input String returns `null`.

           StringUtils.upperCase(null)  = null
           StringUtils.upperCase("")    = ""
           StringUtils.upperCase("aBc") = "ABC"

      Note: As described in the documentation for `String.toUpperCase()`, the result of this method is affected by the current locale. For platform-independent case transformations, the method `lowerCase(String, Locale)` should be used with a specific locale (e.g. `Locale.ENGLISH`).

      Parameters:
        `str` - the String to upper case, may be null
      Returns:
        the upper cased String, `null` if null String input

    - #### upperCase

          public static String upperCase​(String str,
                                         Locale locale)

      Converts a String to upper case as per `String.toUpperCase(Locale)`.

      A `null` input String returns `null`.

           StringUtils.upperCase(null, Locale.ENGLISH)  = null
           StringUtils.upperCase("", Locale.ENGLISH)    = ""
           StringUtils.upperCase("aBc", Locale.ENGLISH) = "ABC"

      Parameters:
        `str` - the String to upper case, may be null
        `locale` - the locale that defines the case transformation rules, must not be null
      Returns:
        the upper cased String, `null` if null String input
      Since:
        2.5

    - #### lowerCase

          public static String lowerCase​(String str)

      Converts a String to lower case as per `String.toLowerCase()`.

      A `null` input String returns `null`.

           StringUtils.lowerCase(null)  = null
           StringUtils.lowerCase("")    = ""
           StringUtils.lowerCase("aBc") = "abc"

      Note: As described in the documentation for `String.toLowerCase()`, the result of this method is affected by the current locale. For platform-independent case transformations, the method `lowerCase(String, Locale)` should be used with a specific locale (e.g. `Locale.ENGLISH`).

      Parameters:
        `str` - the String to lower case, may be null
      Returns:
        the lower cased String, `null` if null String input

    - #### lowerCase

          public static String lowerCase​(String str,
                                         Locale locale)

      Converts a String to lower case as per `String.toLowerCase(Locale)`.

      A `null` input String returns `null`.

           StringUtils.lowerCase(null, Locale.ENGLISH)  = null
           StringUtils.lowerCase("", Locale.ENGLISH)    = ""
           StringUtils.lowerCase("aBc", Locale.ENGLISH) = "abc"

      Parameters:
        `str` - the String to lower case, may be null
        `locale` - the locale that defines the case transformation rules, must not be null
      Returns:
        the lower cased String, `null` if null String input
      Since:
        2.5

    - #### capitalize

          public static String capitalize​(String str)

      Capitalizes a String changing the first letter to title case as per `Character.toTitleCase(char)`. No other letters are changed.

      For a word based algorithm, see `WordUtils.capitalize(String)`. A `null` input String returns `null`.

           StringUtils.capitalize(null)  = null
           StringUtils.capitalize("")    = ""
           StringUtils.capitalize("cat") = "Cat"
           StringUtils.capitalize("cAt") = "CAt"

      Parameters:
        `str` - the String to capitalize, may be null
      Returns:
        the capitalized String, `null` if null String input
      Since:
        2.0
      See Also:
        `WordUtils.capitalize(String)`, `uncapitalize(String)`

    - #### capitalise

          public static String capitalise​(String str)

      Deprecated.
      Use the standardly named `capitalize(String)`. Method will be removed in Commons Lang 3.0.

      Capitalizes a String changing the first letter to title case as per `Character.toTitleCase(char)`. No other letters are changed.

      Parameters:
        `str` - the String to capitalize, may be null
      Returns:
        the capitalized String, `null` if null String input

    - #### uncapitalize

          public static String uncapitalize​(String str)

      Uncapitalizes a String changing the first letter to title case as per `Character.toLowerCase(char)`. No other letters are changed.

      For a word based algorithm, see `WordUtils.uncapitalize(String)`. A `null` input String returns `null`.

           StringUtils.uncapitalize(null)  = null
           StringUtils.uncapitalize("")    = ""
           StringUtils.uncapitalize("Cat") = "cat"
           StringUtils.uncapitalize("CAT") = "cAT"

      Parameters:
        `str` - the String to uncapitalize, may be null
      Returns:
        the uncapitalized String, `null` if null String input
      Since:
        2.0
      See Also:
        `WordUtils.uncapitalize(String)`, `capitalize(String)`

    - #### uncapitalise

          public static String uncapitalise​(String str)

      Deprecated.
      Use the standardly named `uncapitalize(String)`. Method will be removed in Commons Lang 3.0.

      Uncapitalizes a String changing the first letter to title case as per `Character.toLowerCase(char)`. No other letters are changed.

      Parameters:
        `str` - the String to uncapitalize, may be null
      Returns:
        the uncapitalized String, `null` if null String input

    - #### swapCase

          public static String swapCase​(String str)

      Swaps the case of a String changing upper and title case to lower case, and lower case to upper case.

      - Upper case character converts to Lower case
      - Title case character converts to Lower case
      - Lower case character converts to Upper case

      For a word based algorithm, see `WordUtils.swapCase(String)`. A `null` input String returns `null`.

           StringUtils.swapCase(null)                 = null
           StringUtils.swapCase("")                   = ""
           StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"

      NOTE: This method changed in Lang version 2.0. It no longer performs a word based algorithm. If you only use ASCII, you will notice no change. That functionality is available in WordUtils.

      Parameters:
        `str` - the String to swap case, may be null
      Returns:
        the changed String, `null` if null String input

    - #### capitaliseAllWords

          public static String capitaliseAllWords​(String str)

      Deprecated.
      Use the relocated `WordUtils.capitalize(String)`. Method will be removed in Commons Lang 3.0.

      Capitalizes all the whitespace separated words in a String. Only the first letter of each word is changed.

      Whitespace is defined by `Character.isWhitespace(char)`. A `null` input String returns `null`.

      Parameters:
        `str` - the String to capitalize, may be null
      Returns:
        capitalized String, `null` if null String input

    - #### countMatches

          public static int countMatches​(String str,
                                         String sub)

      Counts how many times the substring appears in the larger String.

      A `null` or empty ("") String input returns `0`.

           StringUtils.countMatches(null, *)       = 0
           StringUtils.countMatches("", *)         = 0
           StringUtils.countMatches("abba", null)  = 0
           StringUtils.countMatches("abba", "")    = 0
           StringUtils.countMatches("abba", "a")   = 2
           StringUtils.countMatches("abba", "ab")  = 1
           StringUtils.countMatches("abba", "xxx") = 0

      Parameters:
        `str` - the String to check, may be null
        `sub` - the substring to count, may be null
      Returns:
        the number of occurrences, 0 if either String is `null`

    - #### isAlpha

          public static boolean isAlpha​(String str)

      Checks if the String contains only unicode letters.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isAlpha(null)   = false
           StringUtils.isAlpha("")     = true
           StringUtils.isAlpha("  ")   = false
           StringUtils.isAlpha("abc")  = true
           StringUtils.isAlpha("ab2c") = false
           StringUtils.isAlpha("ab-c") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains letters, and is non-null

    - #### isAlphaSpace

          public static boolean isAlphaSpace​(String str)

      Checks if the String contains only unicode letters and space (' ').

      `null` will return `false` An empty String (length()=0) will return `true`.

           StringUtils.isAlphaSpace(null)   = false
           StringUtils.isAlphaSpace("")     = true
           StringUtils.isAlphaSpace("  ")   = true
           StringUtils.isAlphaSpace("abc")  = true
           StringUtils.isAlphaSpace("ab c") = true
           StringUtils.isAlphaSpace("ab2c") = false
           StringUtils.isAlphaSpace("ab-c") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains letters and space, and is non-null

    - #### isAlphanumeric

          public static boolean isAlphanumeric​(String str)

      Checks if the String contains only unicode letters or digits.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isAlphanumeric(null)   = false
           StringUtils.isAlphanumeric("")     = true
           StringUtils.isAlphanumeric("  ")   = false
           StringUtils.isAlphanumeric("abc")  = true
           StringUtils.isAlphanumeric("ab c") = false
           StringUtils.isAlphanumeric("ab2c") = true
           StringUtils.isAlphanumeric("ab-c") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains letters or digits, and is non-null

    - #### isAlphanumericSpace

          public static boolean isAlphanumericSpace​(String str)

      Checks if the String contains only unicode letters, digits or space (`' '`).

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isAlphanumeric(null)   = false
           StringUtils.isAlphanumeric("")     = true
           StringUtils.isAlphanumeric("  ")   = true
           StringUtils.isAlphanumeric("abc")  = true
           StringUtils.isAlphanumeric("ab c") = true
           StringUtils.isAlphanumeric("ab2c") = true
           StringUtils.isAlphanumeric("ab-c") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains letters, digits or space, and is non-null

    - #### isAsciiPrintable

          public static boolean isAsciiPrintable​(String str)

      Checks if the string contains only ASCII printable characters.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isAsciiPrintable(null)     = false
           StringUtils.isAsciiPrintable("")       = true
           StringUtils.isAsciiPrintable(" ")      = true
           StringUtils.isAsciiPrintable("Ceki")   = true
           StringUtils.isAsciiPrintable("ab2c")   = true
           StringUtils.isAsciiPrintable("!ab-c~") = true
           StringUtils.isAsciiPrintable(" ") = true
           StringUtils.isAsciiPrintable("!") = true
           StringUtils.isAsciiPrintable("~") = true
           StringUtils.isAsciiPrintable("") = false
           StringUtils.isAsciiPrintable("Ceki Gülcü") = false

      Parameters:
        `str` - the string to check, may be null
      Returns:
        `true` if every character is in the range 32 thru 126
      Since:
        2.1

    - #### isNumeric

          public static boolean isNumeric​(String str)

      Checks if the String contains only unicode digits. A decimal point is not a unicode digit and returns false.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isNumeric(null)   = false
           StringUtils.isNumeric("")     = true
           StringUtils.isNumeric("  ")   = false
           StringUtils.isNumeric("123")  = true
           StringUtils.isNumeric("12 3") = false
           StringUtils.isNumeric("ab2c") = false
           StringUtils.isNumeric("12-3") = false
           StringUtils.isNumeric("12.3") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains digits, and is non-null

    - #### isNumericSpace

          public static boolean isNumericSpace​(String str)

      Checks if the String contains only unicode digits or space (`' '`). A decimal point is not a unicode digit and returns false.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isNumeric(null)   = false
           StringUtils.isNumeric("")     = true
           StringUtils.isNumeric("  ")   = true
           StringUtils.isNumeric("123")  = true
           StringUtils.isNumeric("12 3") = true
           StringUtils.isNumeric("ab2c") = false
           StringUtils.isNumeric("12-3") = false
           StringUtils.isNumeric("12.3") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains digits or space, and is non-null

    - #### isWhitespace

          public static boolean isWhitespace​(String str)

      Checks if the String contains only whitespace.

      `null` will return `false`. An empty String (length()=0) will return `true`.

           StringUtils.isWhitespace(null)   = false
           StringUtils.isWhitespace("")     = true
           StringUtils.isWhitespace("  ")   = true
           StringUtils.isWhitespace("abc")  = false
           StringUtils.isWhitespace("ab2c") = false
           StringUtils.isWhitespace("ab-c") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains whitespace, and is non-null
      Since:
        2.0

    - #### isAllLowerCase

          public static boolean isAllLowerCase​(String str)

      Checks if the String contains only lowercase characters.

      `null` will return `false`. An empty String (length()=0) will return `false`.

           StringUtils.isAllLowerCase(null)   = false
           StringUtils.isAllLowerCase("")     = false
           StringUtils.isAllLowerCase("  ")   = false
           StringUtils.isAllLowerCase("abc")  = true
           StringUtils.isAllLowerCase("abC") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains lowercase characters, and is non-null
      Since:
        2.5

    - #### isAllUpperCase

          public static boolean isAllUpperCase​(String str)

      Checks if the String contains only uppercase characters.

      `null` will return `false`. An empty String (length()=0) will return `false`.

           StringUtils.isAllUpperCase(null)   = false
           StringUtils.isAllUpperCase("")     = false
           StringUtils.isAllUpperCase("  ")   = false
           StringUtils.isAllUpperCase("ABC")  = true
           StringUtils.isAllUpperCase("aBC") = false

      Parameters:
        `str` - the String to check, may be null
      Returns:
        `true` if only contains uppercase characters, and is non-null
      Since:
        2.5

    - #### defaultString

          public static String defaultString​(String str)

      Returns either the passed in String, or if the String is `null`, an empty String ("").

           StringUtils.defaultString(null)  = ""
           StringUtils.defaultString("")    = ""
           StringUtils.defaultString("bat") = "bat"

      Parameters:
        `str` - the String to check, may be null
      Returns:
        the passed in String, or the empty String if it was `null`
      See Also:
        `ObjectUtils.toString(Object)`, `String.valueOf(Object)`

    - #### defaultString

          public static String defaultString​(String str,
                                             String defaultStr)

      Returns either the passed in String, or if the String is `null`, the value of `defaultStr`.

           StringUtils.defaultString(null, "NULL")  = "NULL"
           StringUtils.defaultString("", "NULL")    = ""
           StringUtils.defaultString("bat", "NULL") = "bat"

      Parameters:
        `str` - the String to check, may be null
        `defaultStr` - the default String to return if the input is `null`, may be null
      Returns:
        the passed in String, or the default if it was `null`
      See Also:
        `ObjectUtils.toString(Object,String)`, `String.valueOf(Object)`

    - #### defaultIfBlank

          public static String defaultIfBlank​(String str,
                                              String defaultStr)

      Returns either the passed in String, or if the String is whitespace, empty ("") or `null`, the value of `defaultStr`.

           StringUtils.defaultIfBlank(null, "NULL")  = "NULL"
           StringUtils.defaultIfBlank("", "NULL")    = "NULL"
           StringUtils.defaultIfBlank(" ", "NULL")   = "NULL"
           StringUtils.defaultIfBlank("bat", "NULL") = "bat"
           StringUtils.defaultIfBlank("", null)      = null

      Parameters:
        `str` - the String to check, may be null
        `defaultStr` - the default String to return if the input is whitespace, empty ("") or `null`, may be null
      Returns:
        the passed in String, or the default
      Since:
        2.6
      See Also:
        `defaultString(String, String)`

    - #### defaultIfEmpty

          public static String defaultIfEmpty​(String str,
                                              String defaultStr)

      Returns either the passed in String, or if the String is empty or `null`, the value of `defaultStr`.

           StringUtils.defaultIfEmpty(null, "NULL")  = "NULL"
           StringUtils.defaultIfEmpty("", "NULL")    = "NULL"
           StringUtils.defaultIfEmpty("bat", "NULL") = "bat"
           StringUtils.defaultIfEmpty("", null)      = null

      Parameters:
        `str` - the String to check, may be null
        `defaultStr` - the default String to return if the input is empty ("") or `null`, may be null
      Returns:
        the passed in String, or the default
      See Also:
        `defaultString(String, String)`

    - #### reverse

          public static String reverse​(String str)

      Reverses a String as per `StrBuilder.reverse()`.

      A `null` String returns `null`.

           StringUtils.reverse(null)  = null
           StringUtils.reverse("")    = ""
           StringUtils.reverse("bat") = "tab"

      Parameters:
        `str` - the String to reverse, may be null
      Returns:
        the reversed String, `null` if null String input

    - #### reverseDelimited

          public static String reverseDelimited​(String str,
                                                char separatorChar)

      Reverses a String that is delimited by a specific character.

      The Strings between the delimiters are not reversed. Thus java.lang.String becomes String.lang.java (if the delimiter is `'.'`).

           StringUtils.reverseDelimited(null, *)      = null
           StringUtils.reverseDelimited("", *)        = ""
           StringUtils.reverseDelimited("a.b.c", 'x') = "a.b.c"
           StringUtils.reverseDelimited("a.b.c", ".") = "c.b.a"

      Parameters:
        `str` - the String to reverse, may be null
        `separatorChar` - the separator character to use
      Returns:
        the reversed String, `null` if null String input
      Since:
        2.0

    - #### reverseDelimitedString

          public static String reverseDelimitedString​(String str,
                                                      String separatorChars)

      Deprecated.
      Use `reverseDelimited(String, char)` instead. This method is broken as the join doesn't know which char to use. Method will be removed in Commons Lang 3.0.

      Reverses a String that is delimited by a specific character.

      The Strings between the delimiters are not reversed. Thus java.lang.String becomes String.lang.java (if the delimiter is `"."`).

           StringUtils.reverseDelimitedString(null, *)       = null
           StringUtils.reverseDelimitedString("",*)          = ""
           StringUtils.reverseDelimitedString("a.b.c", null) = "a.b.c"
           StringUtils.reverseDelimitedString("a.b.c", ".")  = "c.b.a"

      Parameters:
        `str` - the String to reverse, may be null
        `separatorChars` - the separator characters to use, null treated as whitespace
      Returns:
        the reversed String, `null` if null String input

    - #### abbreviate

          public static String abbreviate​(String str,
                                          int maxWidth)

      Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "Now is the time for..."

      Specifically:

      - If `str` is less than `maxWidth` characters long, return it.
      - Else abbreviate it to `(substring(str, 0, max-3) + "...")`.
      - If `maxWidth` is less than `4`, throw an `IllegalArgumentException`.
      - In no case will it return a String of length greater than `maxWidth`.

           StringUtils.abbreviate(null, *)      = null
           StringUtils.abbreviate("", 4)        = ""
           StringUtils.abbreviate("abcdefg", 6) = "abc..."
           StringUtils.abbreviate("abcdefg", 7) = "abcdefg"
           StringUtils.abbreviate("abcdefg", 8) = "abcdefg"
           StringUtils.abbreviate("abcdefg", 4) = "a..."
           StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException

      Parameters:
        `str` - the String to check, may be null
        `maxWidth` - maximum length of result String, must be at least 4
      Returns:
        abbreviated String, `null` if null String input
      Throws:
        `IllegalArgumentException` - if the width is too small
      Since:
        2.0

    - #### abbreviate

          public static String abbreviate​(String str,
                                          int offset,
                                          int maxWidth)

      Abbreviates a String using ellipses. This will turn "Now is the time for all good men" into "...is the time for..."

      Works like `abbreviate(String, int)`, but allows you to specify a "left edge" offset. Note that this left edge is not necessarily going to be the leftmost character in the result, or the first character following the ellipses, but it will appear somewhere in the result.

      In no case will it return a String of length greater than `maxWidth`.

           StringUtils.abbreviate(null, *, *)                = null
           StringUtils.abbreviate("", 0, 4)                  = ""
           StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..."
           StringUtils.abbreviate("abcdefghijklmno", 0, 10)  = "abcdefg..."
           StringUtils.abbreviate("abcdefghijklmno", 1, 10)  = "abcdefg..."
           StringUtils.abbreviate("abcdefghijklmno", 4, 10)  = "abcdefg..."
           StringUtils.abbreviate("abcdefghijklmno", 5, 10)  = "...fghi..."
           StringUtils.abbreviate("abcdefghijklmno", 6, 10)  = "...ghij..."
           StringUtils.abbreviate("abcdefghijklmno", 8, 10)  = "...ijklmno"
           StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno"
           StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno"
           StringUtils.abbreviate("abcdefghij", 0, 3)        = IllegalArgumentException
           StringUtils.abbreviate("abcdefghij", 5, 6)        = IllegalArgumentException

      Parameters:
        `str` - the String to check, may be null
        `offset` - left edge of source String
        `maxWidth` - maximum length of result String, must be at least 4
      Returns:
        abbreviated String, `null` if null String input
      Throws:
        `IllegalArgumentException` - if the width is too small
      Since:
        2.0

    - #### abbreviateMiddle

          public static String abbreviateMiddle​(String str,
                                                String middle,
                                                int length)

      Abbreviates a String to the length passed, replacing the middle characters with the supplied replacement String.

      This abbreviation only occurs if the following criteria is met:

      - Neither the String for abbreviation nor the replacement String are null or empty
      - The length to truncate to is less than the length of the supplied String
      - The length to truncate to is greater than 0
      - The abbreviated String will have enough room for the length supplied replacement String and the first and last characters of the supplied String for abbreviation
      Otherwise, the returned String will be the same as the supplied String for abbreviation.

           StringUtils.abbreviateMiddle(null, null, 0)      = null
           StringUtils.abbreviateMiddle("abc", null, 0)      = "abc"
           StringUtils.abbreviateMiddle("abc", ".", 0)      = "abc"
           StringUtils.abbreviateMiddle("abc", ".", 3)      = "abc"
           StringUtils.abbreviateMiddle("abcdef", ".", 4)     = "ab.f"

      Parameters:
        `str` - the String to abbreviate, may be null
        `middle` - the String to replace the middle characters with, may be null
        `length` - the length to abbreviate `str` to.
      Returns:
        the abbreviated String if the above criteria is met, or the original String supplied for abbreviation.
      Since:
        2.5

    - #### difference

          public static String difference​(String str1,
                                          String str2)

      Compares two Strings, and returns the portion where they differ. (More precisely, return the remainder of the second String, starting from where it's different from the first.)

      For example, `difference("i am a machine", "i am a robot") -> "robot"`.

           StringUtils.difference(null, null) = null
           StringUtils.difference("", "") = ""
           StringUtils.difference("", "abc") = "abc"
           StringUtils.difference("abc", "") = ""
           StringUtils.difference("abc", "abc") = ""
           StringUtils.difference("ab", "abxyz") = "xyz"
           StringUtils.difference("abcde", "abxyz") = "xyz"
           StringUtils.difference("abcde", "xyz") = "xyz"

      Parameters:
        `str1` - the first String, may be null
        `str2` - the second String, may be null
      Returns:
        the portion of str2 where it differs from str1; returns the empty String if they are equal
      Since:
        2.0

    - #### indexOfDifference

          public static int indexOfDifference​(String str1,
                                              String str2)

      Compares two Strings, and returns the index at which the Strings begin to differ.

      For example, `indexOfDifference("i am a machine", "i am a robot") -> 7`

           StringUtils.indexOfDifference(null, null) = -1
           StringUtils.indexOfDifference("", "") = -1
           StringUtils.indexOfDifference("", "abc") = 0
           StringUtils.indexOfDifference("abc", "") = 0
           StringUtils.indexOfDifference("abc", "abc") = -1
           StringUtils.indexOfDifference("ab", "abxyz") = 2
           StringUtils.indexOfDifference("abcde", "abxyz") = 2
           StringUtils.indexOfDifference("abcde", "xyz") = 0

      Parameters:
        `str1` - the first String, may be null
        `str2` - the second String, may be null
      Returns:
        the index where str2 and str1 begin to differ; -1 if they are equal
      Since:
        2.0

    - #### indexOfDifference

          public static int indexOfDifference​(String[] strs)

      Compares all Strings in an array and returns the index at which the Strings begin to differ.

      For example, `indexOfDifference(new String[] {"i am a machine", "i am a robot"}) -> 7`

           StringUtils.indexOfDifference(null) = -1
           StringUtils.indexOfDifference(new String[] {}) = -1
           StringUtils.indexOfDifference(new String[] {"abc"}) = -1
           StringUtils.indexOfDifference(new String[] {null, null}) = -1
           StringUtils.indexOfDifference(new String[] {"", ""}) = -1
           StringUtils.indexOfDifference(new String[] {"", null}) = 0
           StringUtils.indexOfDifference(new String[] {"abc", null, null}) = 0
           StringUtils.indexOfDifference(new String[] {null, null, "abc"}) = 0
           StringUtils.indexOfDifference(new String[] {"", "abc"}) = 0
           StringUtils.indexOfDifference(new String[] {"abc", ""}) = 0
           StringUtils.indexOfDifference(new String[] {"abc", "abc"}) = -1
           StringUtils.indexOfDifference(new String[] {"abc", "a"}) = 1
           StringUtils.indexOfDifference(new String[] {"ab", "abxyz"}) = 2
           StringUtils.indexOfDifference(new String[] {"abcde", "abxyz"}) = 2
           StringUtils.indexOfDifference(new String[] {"abcde", "xyz"}) = 0
           StringUtils.indexOfDifference(new String[] {"xyz", "abcde"}) = 0
           StringUtils.indexOfDifference(new String[] {"i am a machine", "i am a robot"}) = 7

      Parameters:
        `strs` - array of strings, entries may be null
      Returns:
        the index where the strings begin to differ; -1 if they are all equal
      Since:
        2.4

    - #### getCommonPrefix

          public static String getCommonPrefix​(String[] strs)

      Compares all Strings in an array and returns the initial sequence of characters that is common to all of them.

      For example, `getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) -> "i am a "`

           StringUtils.getCommonPrefix(null) = ""
           StringUtils.getCommonPrefix(new String[] {}) = ""
           StringUtils.getCommonPrefix(new String[] {"abc"}) = "abc"
           StringUtils.getCommonPrefix(new String[] {null, null}) = ""
           StringUtils.getCommonPrefix(new String[] {"", ""}) = ""
           StringUtils.getCommonPrefix(new String[] {"", null}) = ""
           StringUtils.getCommonPrefix(new String[] {"abc", null, null}) = ""
           StringUtils.getCommonPrefix(new String[] {null, null, "abc"}) = ""
           StringUtils.getCommonPrefix(new String[] {"", "abc"}) = ""
           StringUtils.getCommonPrefix(new String[] {"abc", ""}) = ""
           StringUtils.getCommonPrefix(new String[] {"abc", "abc"}) = "abc"
           StringUtils.getCommonPrefix(new String[] {"abc", "a"}) = "a"
           StringUtils.getCommonPrefix(new String[] {"ab", "abxyz"}) = "ab"
           StringUtils.getCommonPrefix(new String[] {"abcde", "abxyz"}) = "ab"
           StringUtils.getCommonPrefix(new String[] {"abcde", "xyz"}) = ""
           StringUtils.getCommonPrefix(new String[] {"xyz", "abcde"}) = ""
           StringUtils.getCommonPrefix(new String[] {"i am a machine", "i am a robot"}) = "i am a "

      Parameters:
        `strs` - array of String objects, entries may be null
      Returns:
        the initial sequence of characters that are common to all Strings in the array; empty String if the array is null, the elements are all null or if there is no common prefix.
      Since:
        2.4

    - #### getLevenshteinDistance

          public static int getLevenshteinDistance​(String s,
                                                   String t)

      Find the Levenshtein distance between two Strings.

      This is the number of changes needed to change one String into another, where each change is a single character modification (deletion, insertion or substitution).

      The previous implementation of the Levenshtein distance algorithm was from http://www.merriampark.com/ld.htm

      Chas Emerick has written an implementation in Java, which avoids an OutOfMemoryError which can occur when my Java implementation is used with very large strings.
      This implementation of the Levenshtein distance algorithm is from http://www.merriampark.com/ldjava.htm

           StringUtils.getLevenshteinDistance(null, *)             = IllegalArgumentException
           StringUtils.getLevenshteinDistance(*, null)             = IllegalArgumentException
           StringUtils.getLevenshteinDistance("","")               = 0
           StringUtils.getLevenshteinDistance("","a")              = 1
           StringUtils.getLevenshteinDistance("aaapppp", "")       = 7
           StringUtils.getLevenshteinDistance("frog", "fog")       = 1
           StringUtils.getLevenshteinDistance("fly", "ant")        = 3
           StringUtils.getLevenshteinDistance("elephant", "hippo") = 7
           StringUtils.getLevenshteinDistance("hippo", "elephant") = 7
           StringUtils.getLevenshteinDistance("hippo", "zzzzzzzz") = 8
           StringUtils.getLevenshteinDistance("hello", "hallo")    = 1

      Parameters:
        `s` - the first String, must not be null
        `t` - the second String, must not be null
      Returns:
        result distance
      Throws:
        `IllegalArgumentException` - if either String input `null`

    - #### startsWith

          public static boolean startsWith​(String str,
                                           String prefix)

      Check if a String starts with a specified prefix.

      `null`s are handled without exceptions. Two `null` references are considered to be equal. The comparison is case sensitive.

           StringUtils.startsWith(null, null)      = true
           StringUtils.startsWith(null, "abc")     = false
           StringUtils.startsWith("abcdef", null)  = false
           StringUtils.startsWith("abcdef", "abc") = true
           StringUtils.startsWith("ABCDEF", "abc") = false

      Parameters:
        `str` - the String to check, may be null
        `prefix` - the prefix to find, may be null
      Returns:
        `true` if the String starts with the prefix, case sensitive, or both `null`
      Since:
        2.4
      See Also:
        `String.startsWith(String)`

    - #### startsWithIgnoreCase

          public static boolean startsWithIgnoreCase​(String str,
                                                     String prefix)

      Case insensitive check if a String starts with a specified prefix.

      `null`s are handled without exceptions. Two `null` references are considered to be equal. The comparison is case insensitive.

           StringUtils.startsWithIgnoreCase(null, null)      = true
           StringUtils.startsWithIgnoreCase(null, "abc")     = false
           StringUtils.startsWithIgnoreCase("abcdef", null)  = false
           StringUtils.startsWithIgnoreCase("abcdef", "abc") = true
           StringUtils.startsWithIgnoreCase("ABCDEF", "abc") = true

      Parameters:
        `str` - the String to check, may be null
        `prefix` - the prefix to find, may be null
      Returns:
        `true` if the String starts with the prefix, case insensitive, or both `null`
      Since:
        2.4
      See Also:
        `String.startsWith(String)`

    - #### startsWithAny

          public static boolean startsWithAny​(String string,
                                              String[] searchStrings)

      Check if a String starts with any of an array of specified strings.

           StringUtils.startsWithAny(null, null)      = false
           StringUtils.startsWithAny(null, new String[] {"abc"})  = false
           StringUtils.startsWithAny("abcxyz", null)     = false
           StringUtils.startsWithAny("abcxyz", new String[] {""}) = false
           StringUtils.startsWithAny("abcxyz", new String[] {"abc"}) = true
           StringUtils.startsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true

      Parameters:
        `string` - the String to check, may be null
        `searchStrings` - the Strings to find, may be null or empty
      Returns:
        `true` if the String starts with any of the the prefixes, case insensitive, or both `null`
      Since:
        2.5
      See Also:
        `startsWith(String, String)`

    - #### endsWith

          public static boolean endsWith​(String str,
                                         String suffix)

      Check if a String ends with a specified suffix.

      `null`s are handled without exceptions. Two `null` references are considered to be equal. The comparison is case sensitive.

           StringUtils.endsWith(null, null)      = true
           StringUtils.endsWith(null, "def")     = false
           StringUtils.endsWith("abcdef", null)  = false
           StringUtils.endsWith("abcdef", "def") = true
           StringUtils.endsWith("ABCDEF", "def") = false
           StringUtils.endsWith("ABCDEF", "cde") = false

      Parameters:
        `str` - the String to check, may be null
        `suffix` - the suffix to find, may be null
      Returns:
        `true` if the String ends with the suffix, case sensitive, or both `null`
      Since:
        2.4
      See Also:
        `String.endsWith(String)`

    - #### endsWithIgnoreCase

          public static boolean endsWithIgnoreCase​(String str,
                                                   String suffix)

      Case insensitive check if a String ends with a specified suffix.

      `null`s are handled without exceptions. Two `null` references are considered to be equal. The comparison is case insensitive.

           StringUtils.endsWithIgnoreCase(null, null)      = true
           StringUtils.endsWithIgnoreCase(null, "def")     = false
           StringUtils.endsWithIgnoreCase("abcdef", null)  = false
           StringUtils.endsWithIgnoreCase("abcdef", "def") = true
           StringUtils.endsWithIgnoreCase("ABCDEF", "def") = true
           StringUtils.endsWithIgnoreCase("ABCDEF", "cde") = false

      Parameters:
        `str` - the String to check, may be null
        `suffix` - the suffix to find, may be null
      Returns:
        `true` if the String ends with the suffix, case insensitive, or both `null`
      Since:
        2.4
      See Also:
        `String.endsWith(String)`

    - #### normalizeSpace

          public static String normalizeSpace​(String str)

      Similar to http://www.w3.org/TR/xpath/#function-normalize -space

      The function returns the argument string with whitespace normalized by using ``trim(String)`` to remove leading and trailing whitespace and then replacing sequences of whitespace characters by a single space.

      In XML Whitespace characters are the same as those allowed by the S production, which is S ::= (#x20 | #x9 | #xD | #xA)+

      See Java's `Character.isWhitespace(char)` for which characters are considered whitespace.

      The difference is that Java's whitespace includes vertical tab and form feed, which this functional will also normalize. Additonally ``trim(String)`` removes control characters (char <= 32) from both ends of this String.

      Parameters:
        `str` - the source String to normalize whitespaces from, may be null
      Returns:
        the modified string with whitespace normalized, `null` if null String input
      Since:
        2.6
      See Also:
        `Character.isWhitespace(char)`, `trim(String)`, <ahref="http://www.w3.org/TR/xpath/#function-normalize-space"> http://www.w3.org/TR/xpath/#function-normalize-space

    - #### endsWithAny

          public static boolean endsWithAny​(String string,
                                            String[] searchStrings)

      Check if a String ends with any of an array of specified strings.

           StringUtils.endsWithAny(null, null)      = false
           StringUtils.endsWithAny(null, new String[] {"abc"})  = false
           StringUtils.endsWithAny("abcxyz", null)     = false
           StringUtils.endsWithAny("abcxyz", new String[] {""}) = true
           StringUtils.endsWithAny("abcxyz", new String[] {"xyz"}) = true
           StringUtils.endsWithAny("abcxyz", new String[] {null, "xyz", "abc"}) = true

      Parameters:
        `string` - the String to check, may be null
        `searchStrings` - the Strings to find, may be null or empty
      Returns:
        `true` if the String ends with any of the the prefixes, case insensitive, or both `null`
      Since:
        2.6