## Uses of Interface
java.util.function.ToLongFunction

Packages that use ToLongFunction
java.util: Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).
java.util.concurrent: Utility classes commonly useful in concurrent programming.
java.util.stream: Classes to support functional-style operations on streams of elements, such as map-reduce transformations on collections.

### Uses of ToLongFunction in java.util

Methods in java.util with parameters of type ToLongFunction
`static <T> Comparator<T>` Comparator.`comparingLong(ToLongFunction<? super T> keyExtractor)` Accepts a function that extracts a `long` sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key.
`default Comparator<T>` Comparator.`thenComparingLong(ToLongFunction<? super T> keyExtractor)` Returns a lexicographic-order comparator with a function that extracts a `long` sort key.

### Uses of ToLongFunction in java.util.concurrent

Methods in java.util.concurrent with parameters of type ToLongFunction
`long` ConcurrentHashMap.`reduceEntriesToLong(long parallelismThreshold, ToLongFunction<Map.Entry<K,V>> transformer, long basis, LongBinaryOperator reducer)` Returns the result of accumulating the given transformation of all entries using the given reducer to combine values, and the given basis as an identity value.
`long` ConcurrentHashMap.`reduceKeysToLong(long parallelismThreshold, ToLongFunction<? super K> transformer, long basis, LongBinaryOperator reducer)` Returns the result of accumulating the given transformation of all keys using the given reducer to combine values, and the given basis as an identity value.
`long` ConcurrentHashMap.`reduceValuesToLong(long parallelismThreshold, ToLongFunction<? super V> transformer, long basis, LongBinaryOperator reducer)` Returns the result of accumulating the given transformation of all values using the given reducer to combine values, and the given basis as an identity value.

### Uses of ToLongFunction in java.util.stream

Methods in java.util.stream with parameters of type ToLongFunction
`static <T> Collector<T,?,Double>` Collectors.`averagingLong(ToLongFunction<? super T> mapper)` Returns a `Collector` that produces the arithmetic mean of a long-valued function applied to the input elements.
`LongStream` Stream.`mapToLong(ToLongFunction<? super T> mapper)` Returns a `LongStream` consisting of the results of applying the given function to the elements of this stream.
`static <T> Collector<T,?,LongSummaryStatistics>` Collectors.`summarizingLong(ToLongFunction<? super T> mapper)` Returns a `Collector` which applies an `long`-producing mapping function to each input element, and returns summary statistics for the resulting values.
`static <T> Collector<T,?,Long>` Collectors.`summingLong(ToLongFunction<? super T> mapper)` Returns a `Collector` that produces the sum of a long-valued function applied to the input elements.