Package com.github.ferstl.streams

Class ParallelStreamSupport<T>

java.lang.Object

com.github.ferstl.streams.ParallelStreamSupport<T>

Type Parameters:

T - The type of the stream elements.

All Implemented Interfaces:

AutoCloseable, BaseStream<T,Stream<T>>, Stream<T>

public class ParallelStreamSupport<T>
extends Object
implements Stream<T>

An implementation of Stream which uses a custom ForkJoinPool for parallel aggregate operations.

The following example illustrates an aggregate operation using ParallelStreamSupport with a custom ForkJoinPool:

 ForkJoinPool pool = new ForkJoinPool();
 int sum = ParallelStreamSupport.parallelStream(widgets, pool)
     .filter(w -> w.getColor() == RED)
     .mapToInt(w -> w.getWeight())
     .sum();
 

In case this stream is configured for parallel execution, i.e. BaseStream.isParallel() returns true, a terminal operation will be executed as ForkJoinTask in the custom ForkJoinPool. Otherwise it will be executed in the calling thread.

This implementation offers various factory methods which are based on:

• The static factory methods of Stream, which are meaningful for parallel streams
• Collection.parallelStream()
• Arrays.stream(Object[])
• StreamSupport.stream(Spliterator, boolean)
• StreamSupport.stream(Supplier, int, boolean)

API Note:

Internally, this stream wraps a stream which is initially created in one of the static factory methods. Whenever a non-terminal operation is called the underlying stream will be replaced with the result of calling the same method on that stream. The return value of these operations is always this stream or, in case of operations that return a different type of stream, one of ParallelIntStreamSupport, ParallelLongStreamSupport or ParallelDoubleStreamSupport.

Although each factory method returns a parallel stream, calling BaseStream.sequential() is still possible and leads to sequential execution of a terminal operation within the calling thread.

Implementation Note:

See the class documentation for Stream and the package documentation for java.util.stream for additional specification.

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.stream.Stream

Stream.Builder<T extends Object>

Method Summary

Modifier and Type	Method	Description
boolean	allMatch(Predicate<? super T> predicate)
boolean	anyMatch(Predicate<? super T> predicate)
void	close()
<R> R	collect(Supplier<R> supplier, BiConsumer<R,? super T> accumulator, BiConsumer<R,R> combiner)
<R,A> R	collect(Collector<? super T,A,R> collector)
static <T> Stream<T>	concat(Stream<? extends T> a, Stream<? extends T> b, ForkJoinPool workerPool)	Creates a lazily concatenated parallel stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
long	count()
Stream<T>	distinct()
Stream<T>	dropWhile(Predicate<? super T> predicate)
protected void	execute(Runnable terminalOperation)
protected <R> R	execute(Callable<R> terminalOperation)
Stream<T>	filter(Predicate<? super T> predicate)
Optional<T>	findAny()
Optional<T>	findFirst()
<R> Stream<R>	flatMap(Function<? super T,? extends Stream<? extends R>> mapper)
DoubleStream	flatMapToDouble(Function<? super T,? extends DoubleStream> mapper)
IntStream	flatMapToInt(Function<? super T,? extends IntStream> mapper)
LongStream	flatMapToLong(Function<? super T,? extends LongStream> mapper)
void	forEach(Consumer<? super T> action)
void	forEachOrdered(Consumer<? super T> action)
static <T> Stream<T>	generate(Supplier<T> supplier, ForkJoinPool workerPool)	Creates a parallel infinite sequential unordered stream where each element is generated by the provided Supplier.
boolean	isParallel()
static <T> Stream<T>	iterate(T seed, UnaryOperator<T> operator, ForkJoinPool workerPool)	Creates a parallel infinite ordered stream produced by iterative application of a function f to an initial element seed.
Iterator<T>	iterator()
Stream<T>	limit(long maxSize)
<R> Stream<R>	map(Function<? super T,? extends R> mapper)
DoubleStream	mapToDouble(ToDoubleFunction<? super T> mapper)
IntStream	mapToInt(ToIntFunction<? super T> mapper)
LongStream	mapToLong(ToLongFunction<? super T> mapper)
Optional<T>	max(Comparator<? super T> comparator)
Optional<T>	min(Comparator<? super T> comparator)
boolean	noneMatch(Predicate<? super T> predicate)
S	onClose(Runnable closeHandler)
S	parallel()
static <T> Stream<T>	parallelStream(Collection<T> collection, ForkJoinPool workerPool)	Creates a parallel stream from the given Collection.
static <T> Stream<T>	parallelStream(Supplier<? extends Spliterator<T>> supplier, int characteristics, ForkJoinPool workerPool)	Creates a parallel stream from the given Spliterator supplier.
static <T> Stream<T>	parallelStream(Spliterator<T> spliterator, ForkJoinPool workerPool)	Creates a parallel stream from the given Spliterator.
static <T> Stream<T>	parallelStream(Stream.Builder<T> builder, ForkJoinPool workerPool)	Creates a parallel stream from the given Stream.Builder.
static <T> Stream<T>	parallelStream(T[] array, ForkJoinPool workerPool)	Creates a parallel stream from the given Array.
Stream<T>	peek(Consumer<? super T> action)
Optional<T>	reduce(BinaryOperator<T> accumulator)
T	reduce(T identity, BinaryOperator<T> accumulator)
<U> U	reduce(U identity, BiFunction<U,? super T,U> accumulator, BinaryOperator<U> combiner)
S	sequential()
Stream<T>	skip(long n)
Stream<T>	sorted()
Stream<T>	sorted(Comparator<? super T> comparator)
Spliterator<T>	spliterator()
Stream<T>	takeWhile(Predicate<? super T> predicate)
Object[]	toArray()
<A> A[]	toArray(IntFunction<A[]> generator)
S	unordered()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.stream.BaseStream

close, isParallel, iterator, onClose, parallel, sequential, spliterator, unordered

Method Detail

parallelStream

public static <T> Stream<T> parallelStream(Collection<T> collection,
                                           ForkJoinPool workerPool)

Creates a parallel stream from the given Collection. This operation is similar to Collection.parallelStream() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

collection - Collection to create the parallel stream from. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Collection.parallelStream()

parallelStream

public static <T> Stream<T> parallelStream(T[] array,
                                           ForkJoinPool workerPool)

Creates a parallel stream from the given Array. This operation is similar to calling Arrays.stream(array).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

array - Array to create the parallel stream from. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Arrays.stream(Object[])

parallelStream

public static <T> Stream<T> parallelStream(Spliterator<T> spliterator,
                                           ForkJoinPool workerPool)

Creates a parallel stream from the given Spliterator. This operation is similar to calling StreamSupport.stream(spliterator, true) with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

spliterator - A Spliterator describing the stream elements. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

StreamSupport.stream(Spliterator, boolean)

parallelStream

public static <T> Stream<T> parallelStream(Supplier<? extends Spliterator<T>> supplier,
                                           int characteristics,
                                           ForkJoinPool workerPool)

Creates a parallel stream from the given Spliterator supplier. This operation is similar to calling StreamSupport.stream(supplier, characteristics, true) with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

supplier - A Supplier of a Spliterator. Must not be null.

characteristics - Spliterator characteristics of the supplied Spliterator. The characteristics must be equal to supplier.get().characteristics(), otherwise undefined behavior may occur when terminal operation commences.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

StreamSupport.stream(Supplier, int, boolean)

parallelStream

public static <T> Stream<T> parallelStream(Stream.Builder<T> builder,
                                           ForkJoinPool workerPool)

Creates a parallel stream from the given Stream.Builder. This operation is similar to calling builder.build().parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

builder - The builder to create the stream from. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Stream.builder()

iterate

public static <T> Stream<T> iterate(T seed,
                                    UnaryOperator<T> operator,
                                    ForkJoinPool workerPool)

Creates a parallel infinite ordered stream produced by iterative application of a function f to an initial element seed. This operation is similar to calling Stream.iterate(seed, operator).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

seed - The initial element.

operator - A function to be applied to to the previous element to produce a new element. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Stream.iterate(Object, UnaryOperator)

generate

public static <T> Stream<T> generate(Supplier<T> supplier,
                                     ForkJoinPool workerPool)

Creates a parallel infinite sequential unordered stream where each element is generated by the provided Supplier. This operation is similar to calling Stream.generate(supplier).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

supplier - The Supplier of generated elements. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Stream.generate(Supplier)

concat

public static <T> Stream<T> concat(Stream<? extends T> a,
                                   Stream<? extends T> b,
                                   ForkJoinPool workerPool)

Creates a lazily concatenated parallel stream whose elements are all the elements of the first stream followed by all the elements of the second stream. This operation is similar to calling Stream.concat(a, b).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Type Parameters:

T - The type of stream elements.

Parameters:

a - The first stream. Must not be null.

b - The second stream. Must not be null.

workerPool - Thread pool for parallel execution of a terminal operation. Must not be null.

Returns:

A parallel stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Stream.concat(Stream, Stream)

filter

public Stream<T> filter(Predicate<? super T> predicate)

Specified by:

filter in interface Stream<T>

map

public <R> Stream<R> map(Function<? super T,? extends R> mapper)

Specified by:

map in interface Stream<T>

mapToInt

public IntStream mapToInt(ToIntFunction<? super T> mapper)

Specified by:

mapToInt in interface Stream<T>

mapToLong

public LongStream mapToLong(ToLongFunction<? super T> mapper)

Specified by:

mapToLong in interface Stream<T>

mapToDouble

public DoubleStream mapToDouble(ToDoubleFunction<? super T> mapper)

Specified by:

mapToDouble in interface Stream<T>

flatMap

public <R> Stream<R> flatMap(Function<? super T,? extends Stream<? extends R>> mapper)

Specified by:

flatMap in interface Stream<T>

flatMapToInt

public IntStream flatMapToInt(Function<? super T,? extends IntStream> mapper)

Specified by:

flatMapToInt in interface Stream<T>

flatMapToLong

public LongStream flatMapToLong(Function<? super T,? extends LongStream> mapper)

Specified by:

flatMapToLong in interface Stream<T>

flatMapToDouble

public DoubleStream flatMapToDouble(Function<? super T,? extends DoubleStream> mapper)

Specified by:

flatMapToDouble in interface Stream<T>

distinct

public Stream<T> distinct()

Specified by:

distinct in interface Stream<T>

sorted

public Stream<T> sorted()

Specified by:

sorted in interface Stream<T>

sorted

public Stream<T> sorted(Comparator<? super T> comparator)

Specified by:

sorted in interface Stream<T>

peek

public Stream<T> peek(Consumer<? super T> action)

Specified by:

peek in interface Stream<T>

limit

public Stream<T> limit(long maxSize)

Specified by:

limit in interface Stream<T>

skip

public Stream<T> skip(long n)

Specified by:

skip in interface Stream<T>

takeWhile

public Stream<T> takeWhile(Predicate<? super T> predicate)

Specified by:

takeWhile in interface Stream<T>

dropWhile

public Stream<T> dropWhile(Predicate<? super T> predicate)

Specified by:

dropWhile in interface Stream<T>

forEach

public void forEach(Consumer<? super T> action)

Specified by:

forEach in interface Stream<T>

forEachOrdered

public void forEachOrdered(Consumer<? super T> action)

Specified by:

forEachOrdered in interface Stream<T>

toArray

public Object[] toArray()

Specified by:

toArray in interface Stream<T>

toArray

public <A> A[] toArray(IntFunction<A[]> generator)

Specified by:

toArray in interface Stream<T>

reduce

public T reduce(T identity,
                BinaryOperator<T> accumulator)

Specified by:

reduce in interface Stream<T>

reduce

public Optional<T> reduce(BinaryOperator<T> accumulator)

Specified by:

reduce in interface Stream<T>

reduce

public <U> U reduce(U identity,
                    BiFunction<U,? super T,U> accumulator,
                    BinaryOperator<U> combiner)

Specified by:

reduce in interface Stream<T>

collect

public <R> R collect(Supplier<R> supplier,
                     BiConsumer<R,? super T> accumulator,
                     BiConsumer<R,R> combiner)

Specified by:

collect in interface Stream<T>

collect

public <R,A> R collect(Collector<? super T,A,R> collector)

Specified by:

collect in interface Stream<T>

min

public Optional<T> min(Comparator<? super T> comparator)

Specified by:

min in interface Stream<T>

max

public Optional<T> max(Comparator<? super T> comparator)

Specified by:

max in interface Stream<T>

count

public long count()

Specified by:

count in interface Stream<T>

anyMatch

public boolean anyMatch(Predicate<? super T> predicate)

Specified by:

anyMatch in interface Stream<T>

allMatch

public boolean allMatch(Predicate<? super T> predicate)

Specified by:

allMatch in interface Stream<T>

noneMatch

public boolean noneMatch(Predicate<? super T> predicate)

Specified by:

noneMatch in interface Stream<T>

findFirst

public Optional<T> findFirst()

Specified by:

findFirst in interface Stream<T>

findAny

public Optional<T> findAny()

Specified by:

findAny in interface Stream<T>

isParallel

public boolean isParallel()

Specified by:

isParallel in interface BaseStream<T,S extends BaseStream<T,S>>

iterator

public Iterator<T> iterator()

Specified by:

iterator in interface BaseStream<T,S extends BaseStream<T,S>>

spliterator

public Spliterator<T> spliterator()

Specified by:

spliterator in interface BaseStream<T,S extends BaseStream<T,S>>

sequential

public S sequential()

Specified by:

sequential in interface BaseStream<T,S extends BaseStream<T,S>>

parallel

public S parallel()

Specified by:

parallel in interface BaseStream<T,S extends BaseStream<T,S>>

unordered

public S unordered()

Specified by:

unordered in interface BaseStream<T,S extends BaseStream<T,S>>

onClose

public S onClose(Runnable closeHandler)

Specified by:

onClose in interface BaseStream<T,S extends BaseStream<T,S>>

close

public void close()

Specified by:

close in interface AutoCloseable

Specified by:

close in interface BaseStream<T,S extends BaseStream<T,S>>

execute

protected void execute(Runnable terminalOperation)

execute

protected <R> R execute(Callable<R> terminalOperation)