# Package org.apache.lucene.util

Some utility classes.

See: Description

- Interface Summary
  Interface | Description
  --- | ---
  Attribute | Base interface for attributes.

- Class Summary
  Class | Description
  --- | ---
  ArrayUtil | Methods for manipulating arrays.
  AttributeImpl | Base class for Attributes that can be added to a `AttributeSource`.
  AttributeSource | An AttributeSource contains a list of different `AttributeImpl`s, and methods to add and get them.
  AttributeSource.AttributeFactory | An AttributeFactory creates instances of `AttributeImpl`s.
  AttributeSource.State | This class holds the state of an AttributeSource.
  AverageGuessMemoryModel | An average, best guess, MemoryModel that should work okay on most systems.
  BitUtil | A variety of high efficiency bit twiddling routines.
  BitVector | Optimized implementation of a vector of bits.
  CloseableThreadLocal | Java's builtin ThreadLocal has a serious flaw: it can take an arbitrarily long amount of time to dereference the things you had stored in it, even once the ThreadLocal instance itself is no longer referenced.
  Constants | Some useful constants.
  DocIdBitSet | Simple DocIdSet and DocIdSetIterator backed by a BitSet
  FieldCacheSanityChecker | Provides methods for sanity checking that entries in the FieldCache are not wasteful or inconsistent.
  FieldCacheSanityChecker.Insanity | Simple container for a collection of related CacheEntry objects that in conjunction with each other represent some "insane" usage of the FieldCache.
  FieldCacheSanityChecker.InsanityType | An Enumeration of the different types of "insane" behavior that may be detected in a FieldCache.
  IndexableBinaryStringTools | Provides support for converting byte sequences to Strings and back again.
  MapOfSets | Helper class for keeping Lists of Objects associated with keys.
  MemoryModel | Returns primitive memory sizes for estimating RAM usage.
  NumericUtils | This is a helper class to generate prefix-encoded representations for numerical values and supplies converters to represent float/double values as sortable integers/longs.
  NumericUtils.IntRangeBuilder | Expert: Callback for `NumericUtils.splitIntRange(org.apache.lucene.util.NumericUtils.IntRangeBuilder, int, int, int)`.
  NumericUtils.LongRangeBuilder | Expert: Callback for `NumericUtils.splitLongRange(org.apache.lucene.util.NumericUtils.LongRangeBuilder, int, long, long)`.
  OpenBitSet | An "open" BitSet implementation that allows direct access to the array of words storing the bits.
  OpenBitSetDISI |
  OpenBitSetIterator | An iterator to iterate over set bits in an OpenBitSet.
  Parameter | A serializable Enum class.
  PriorityQueue | A PriorityQueue maintains a partial ordering of its elements such that the least element can always be found in constant time.
  RamUsageEstimator | Estimates the size of a given Object using a given MemoryModel for primitive size information.
  ReaderUtil | Common util methods for dealing with `IndexReader`s.
  ScorerDocQueue | A ScorerDocQueue maintains a partial ordering of its Scorers such that the least Scorer can always be found in constant time.
  SimpleStringInterner | Simple lockless and memory barrier free String intern cache that is guaranteed to return the same String instance as String.intern() does.
  SmallFloat | Floating point numbers smaller than 32 bits.
  SortedVIntList | Stores and iterate on sorted integers in compressed form in RAM.
  SorterTemplate | Borrowed from Cglib.
  StringHelper | Methods for manipulating strings.
  StringInterner | Subclasses of StringInterner are required to return the same single String object for all equal strings.
  ToStringUtils | Helper methods to ease implementing `Object.toString()`.
  UnicodeUtil | Class to encode java's UTF16 char[] into UTF8 byte[] without always allocating a new byte[] as String.getBytes("UTF-8") does.
  UnicodeUtil.UTF16Result |
  UnicodeUtil.UTF8Result |
  Version | Use by certain classes to match version compatibility across releases of Lucene.

## Package org.apache.lucene.util Description

Some utility classes.

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