| Package | Description | 
|---|---|
| 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. 
 | 
| Modifier and Type | Method and Description | 
|---|---|
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. | 
| Modifier and Type | Method and Description | 
|---|---|
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. 
 | 
| Modifier and Type | Method and Description | 
|---|---|
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. | 
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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