| 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.comparingDouble(ToDoubleFunction<? super T> keyExtractor)
Accepts a function that extracts a  
double sort key from a type
 T, and returns a Comparator<T> that compares by that
 sort key. | 
default Comparator<T> | 
Comparator.thenComparingDouble(ToDoubleFunction<? super T> keyExtractor)
Returns a lexicographic-order comparator with a function that
 extracts a  
double sort key. | 
| Modifier and Type | Method and Description | 
|---|---|
double | 
ConcurrentHashMap.reduceEntriesToDouble(long parallelismThreshold,
                     ToDoubleFunction<Map.Entry<K,V>> transformer,
                     double basis,
                     DoubleBinaryOperator 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. 
 | 
double | 
ConcurrentHashMap.reduceKeysToDouble(long parallelismThreshold,
                  ToDoubleFunction<? super K> transformer,
                  double basis,
                  DoubleBinaryOperator 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. 
 | 
double | 
ConcurrentHashMap.reduceValuesToDouble(long parallelismThreshold,
                    ToDoubleFunction<? super V> transformer,
                    double basis,
                    DoubleBinaryOperator 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.averagingDouble(ToDoubleFunction<? super T> mapper)
Returns a  
Collector that produces the arithmetic mean of a double-valued
 function applied to the input elements. | 
DoubleStream | 
Stream.mapToDouble(ToDoubleFunction<? super T> mapper)
Returns a  
DoubleStream consisting of the results of applying the
 given function to the elements of this stream. | 
static <T> Collector<T,?,DoubleSummaryStatistics> | 
Collectors.summarizingDouble(ToDoubleFunction<? super T> mapper)
Returns a  
Collector which applies an double-producing
 mapping function to each input element, and returns summary statistics
 for the resulting values. | 
static <T> Collector<T,?,Double> | 
Collectors.summingDouble(ToDoubleFunction<? super T> mapper)
Returns a  
Collector that produces the sum of a double-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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