no.digipost

Class DiggCollectors

java.lang.Object

no.digipost.DiggCollectors

public final class DiggCollectors
extends Object

Various Collector implementations.

Method Summary

Modifier and Type	Method and Description
static <T,A,R> AdaptableCollector<T,A,R>	adapt(Collector<T,A,R> collector) Deprecated. Use Collectors.collectingAndThen(Collector, Function) instead.
static <T> AdaptableCollector<T,OneTimeAssignment<T>,Optional<T>>	allowAtMostOne() This is a collector for accessing the expected singular only element of a Stream, as it will throw an exception if more than one element is processed.
static <T> AdaptableCollector<T,OneTimeAssignment<T>,Optional<T>>	allowAtMostOneOrElseThrow(BiFunction<? super T,? super T,? extends RuntimeException> exceptionOnExcessiveElements) This is a collector for accessing the expected singular only element of a Stream, as it will throw the exception yielded from the given function if more than one element is processed.
static <T1,T2> AdaptableCollector<ViewableAsTuple<T1,Optional<T2>>,?,Map<T1,List<T2>>>	toMultimap() A multimap maps from keys to lists, and this collector will arrange tuples by putting each distinct first tuple-element as keys of the resulting map, mapping them to a List, and adding each second tuple-element to the list.
static <T,K,V> AdaptableCollector<T,?,Map<K,List<V>>>	toMultimap(Function<? super T,K> keyExtractor, Function<? super T,Optional<V>> extractor)
static <T,V> AdaptableCollector<T,?,Map<T,List<V>>>	toMultimap(Function<? super T,Optional<V>> extractor)

Methods inherited from class java.lang.Object

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

Method Detail

toMultimap

public static <T1,T2> AdaptableCollector<ViewableAsTuple<T1,Optional<T2>>,?,Map<T1,List<T2>>> toMultimap()

A multimap maps from keys to lists, and this collector will arrange tuples by putting each distinct first tuple-element as keys of the resulting map, mapping them to a List, and adding each second tuple-element to the list.

Type Parameters:

T1 - The type of the first tuple element, which will become the key type of the resulting Map.

T2 - The type of the second tuple element, which will become the List<T2> value type of the resulting Map.

Returns:

the multimap collector.

toMultimap

public static <T,V> AdaptableCollector<T,?,Map<T,List<V>>> toMultimap(Function<? super T,Optional<V>> extractor)

toMultimap

public static <T,K,V> AdaptableCollector<T,?,Map<K,List<V>>> toMultimap(Function<? super T,K> keyExtractor,
                                                                        Function<? super T,Optional<V>> extractor)

allowAtMostOne

public static <T> AdaptableCollector<T,OneTimeAssignment<T>,Optional<T>> allowAtMostOne()

This is a collector for accessing the expected singular only element of a Stream, as it will throw an exception if more than one element is processed. This should be used in preference of the Stream.findFirst() or Stream.findAny() when it is imperative that the stream indeed yields a maximum of one single element, and any more elements is considered a programming error.

Returns:

the collector

allowAtMostOneOrElseThrow

public static <T> AdaptableCollector<T,OneTimeAssignment<T>,Optional<T>> allowAtMostOneOrElseThrow(BiFunction<? super T,? super T,? extends RuntimeException> exceptionOnExcessiveElements)

This is a collector for accessing the expected singular only element of a Stream, as it will throw the exception yielded from the given function if more than one element is processed.

Parameters:

the - function will be given the first element yielded from the stream as its first argument and the unexpected excess one as the second, which may be used to construct an exception to be thrown.

Returns:

the collector

See Also:

allowAtMostOne()

adapt

@Deprecated
public static <T,A,R> AdaptableCollector<T,A,R> adapt(Collector<T,A,R> collector)

Deprecated. Use Collectors.collectingAndThen(Collector, Function) instead.

Turn any Collector into an AdaptableCollector.

Parameters:

collector - the collector to convert

Returns:

the AdaptableCollector

See Also:

AdaptableCollector