Package com.github.ferstl.streams

Class ParallelIntStreamSupport

java.lang.Object

com.github.ferstl.streams.ParallelIntStreamSupport

All Implemented Interfaces:

AutoCloseable, BaseStream<Integer,IntStream>, IntStream

public class ParallelIntStreamSupport
extends Object
implements IntStream

An implementation of IntStream which uses a custom ForkJoinPool for parallel aggregate operations. This is the int primitive specialization of ParallelStreamSupport.

The following example illustrates an aggregate operation using ParallelStreamSupport and ParallelIntStreamSupport with a custom ForkJoinPool, computing the sum of the weights of the red widgets:

 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 IntStream, which are meaningful for parallel streams
• Arrays.stream(int[])
• StreamSupport.intStream(Spliterator.OfInt, boolean)
• StreamSupport.intStream(Supplier, int, boolean)

API Note:

Internally, this stream wraps an int 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 ParallelStreamSupport, 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.IntStream

IntStream.Builder

Method Summary

Modifier and Type	Method	Description
boolean	allMatch(IntPredicate predicate)
boolean	anyMatch(IntPredicate predicate)
DoubleStream	asDoubleStream()
LongStream	asLongStream()
OptionalDouble	average()
Stream<Integer>	boxed()
void	close()
<R> R	collect(Supplier<R> supplier, ObjIntConsumer<R> accumulator, BiConsumer<R,R> combiner)
static IntStream	concat(IntStream a, IntStream b, ForkJoinPool workerPool)	Creates a lazily concatenated parallel int stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
long	count()
IntStream	distinct()
IntStream	dropWhile(IntPredicate predicate)
protected void	execute(Runnable terminalOperation)
protected <R> R	execute(Callable<R> terminalOperation)
IntStream	filter(IntPredicate predicate)
OptionalInt	findAny()
OptionalInt	findFirst()
IntStream	flatMap(IntFunction<? extends IntStream> mapper)
void	forEach(IntConsumer action)
void	forEachOrdered(IntConsumer action)
static IntStream	generate(IntSupplier supplier, ForkJoinPool workerPool)	Creates a parallel infinite sequential unordered int stream where each element is generated by the provided IntSupplier.
boolean	isParallel()
static IntStream	iterate(int seed, IntUnaryOperator operator, ForkJoinPool workerPool)	Creates a parallel infinite ordered int stream produced by iterative application of a function f to an initial element seed.
PrimitiveIterator.OfInt	iterator()
IntStream	limit(long maxSize)
IntStream	map(IntUnaryOperator mapper)
DoubleStream	mapToDouble(IntToDoubleFunction mapper)
LongStream	mapToLong(IntToLongFunction mapper)
<U> Stream<U>	mapToObj(IntFunction<? extends U> mapper)
OptionalInt	max()
OptionalInt	min()
boolean	noneMatch(IntPredicate predicate)
S	onClose(Runnable closeHandler)
S	parallel()
static IntStream	parallelStream(int[] array, ForkJoinPool workerPool)	Creates a parallel int stream from the given Array.
static IntStream	parallelStream(Supplier<? extends Spliterator.OfInt> supplier, int characteristics, ForkJoinPool workerPool)	Creates a parallel int stream from the given Spliterator supplier.
static IntStream	parallelStream(Spliterator.OfInt spliterator, ForkJoinPool workerPool)	Creates a parallel int stream from the given Spliterator.
static IntStream	parallelStream(IntStream.Builder builder, ForkJoinPool workerPool)	Creates a parallel int stream from the given IntStream.Builder.
IntStream	peek(IntConsumer action)
static IntStream	range(int startInclusive, int endExclusive, ForkJoinPool workerPool)	Creates a parallel ordered int stream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1.
static IntStream	rangeClosed(int startInclusive, int endInclusive, ForkJoinPool workerPool)	Creates a parallel ordered int stream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1.
int	reduce(int identity, IntBinaryOperator op)
OptionalInt	reduce(IntBinaryOperator op)
S	sequential()
IntStream	skip(long n)
IntStream	sorted()
Spliterator.OfInt	spliterator()
int	sum()
IntSummaryStatistics	summaryStatistics()
IntStream	takeWhile(IntPredicate predicate)
int[]	toArray()
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, onClose, unordered

Methods inherited from interface java.util.stream.IntStream

parallel, sequential

Method Detail

parallelStream

public static IntStream parallelStream(int[] array,
                                       ForkJoinPool workerPool)

Creates a parallel int 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.

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 int stream that executes a terminal operation in the given ForkJoinPool.

See Also:

Arrays.stream(int[])

parallelStream

public static IntStream parallelStream(Spliterator.OfInt spliterator,
                                       ForkJoinPool workerPool)

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

Parameters:

spliterator - A Spliterator.OfInt 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 int stream that executes a terminal operation in the given ForkJoinPool.

See Also:

StreamSupport.intStream(Spliterator.OfInt, boolean)

parallelStream

public static IntStream parallelStream(Supplier<? extends Spliterator.OfInt> supplier,
                                       int characteristics,
                                       ForkJoinPool workerPool)

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

Parameters:

supplier - A Supplier of a Spliterator.OfInt. 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 int stream that executes a terminal operation in the given ForkJoinPool.

See Also:

StreamSupport.intStream(Supplier, int, boolean)

parallelStream

public static IntStream parallelStream(IntStream.Builder builder,
                                       ForkJoinPool workerPool)

Creates a parallel int stream from the given IntStream.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.

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 int stream that executes a terminal operation in the given ForkJoinPool.

See Also:

IntStream.builder()

iterate

public static IntStream iterate(int seed,
                                IntUnaryOperator operator,
                                ForkJoinPool workerPool)

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

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 int stream that executes a terminal operation in the given ForkJoinPool.

See Also:

IntStream.iterate(int, IntUnaryOperator)

generate

public static IntStream generate(IntSupplier supplier,
                                 ForkJoinPool workerPool)

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

Parameters:

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

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

Returns:

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

See Also:

IntStream.generate(IntSupplier)

range

public static IntStream range(int startInclusive,
                              int endExclusive,
                              ForkJoinPool workerPool)

Creates a parallel ordered int stream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1. This operation is similar to calling IntStream.range(startInclusive, endExclusive).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Parameters:

startInclusive - the (inclusive) initial value

endExclusive - the exclusive upper bound

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

Returns:

A parallel int stream that executes a terminal operation in the given ForkJoinPool for the range of int elements.

See Also:

IntStream.range(int, int)

rangeClosed

public static IntStream rangeClosed(int startInclusive,
                                    int endInclusive,
                                    ForkJoinPool workerPool)

Creates a parallel ordered int stream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1. This operation is similar to calling IntStream.rangeClosed(startInclusive, endInclusive).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

Parameters:

startInclusive - the (inclusive) initial value

endInclusive - the inclusive upper bound

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

Returns:

A parallel int stream that executes a terminal operation in the given ForkJoinPool for the range of int elements.

See Also:

IntStream.rangeClosed(int, int)

concat

public static IntStream concat(IntStream a,
                               IntStream b,
                               ForkJoinPool workerPool)

Creates a lazily concatenated parallel int 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 IntStream.concat(a, b).parallel() with the difference that a parallel terminal operation will be executed in the given ForkJoinPool.

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:

IntStream.concat(IntStream, IntStream)

filter

public IntStream filter(IntPredicate predicate)

Specified by:

filter in interface IntStream

map

public IntStream map(IntUnaryOperator mapper)

Specified by:

map in interface IntStream

mapToObj

public <U> Stream<U> mapToObj(IntFunction<? extends U> mapper)

Specified by:

mapToObj in interface IntStream

mapToLong

public LongStream mapToLong(IntToLongFunction mapper)

Specified by:

mapToLong in interface IntStream

mapToDouble

public DoubleStream mapToDouble(IntToDoubleFunction mapper)

Specified by:

mapToDouble in interface IntStream

flatMap

public IntStream flatMap(IntFunction<? extends IntStream> mapper)

Specified by:

flatMap in interface IntStream

distinct

public IntStream distinct()

Specified by:

distinct in interface IntStream

sorted

public IntStream sorted()

Specified by:

sorted in interface IntStream

peek

public IntStream peek(IntConsumer action)

Specified by:

peek in interface IntStream

limit

public IntStream limit(long maxSize)

Specified by:

limit in interface IntStream

skip

public IntStream skip(long n)

Specified by:

skip in interface IntStream

takeWhile

public IntStream takeWhile(IntPredicate predicate)

Specified by:

takeWhile in interface IntStream

dropWhile

public IntStream dropWhile(IntPredicate predicate)

Specified by:

dropWhile in interface IntStream

forEach

public void forEach(IntConsumer action)

Specified by:

forEach in interface IntStream

forEachOrdered

public void forEachOrdered(IntConsumer action)

Specified by:

forEachOrdered in interface IntStream

toArray

public int[] toArray()

Specified by:

toArray in interface IntStream

reduce

public int reduce(int identity,
                  IntBinaryOperator op)

Specified by:

reduce in interface IntStream

reduce

public OptionalInt reduce(IntBinaryOperator op)

Specified by:

reduce in interface IntStream

collect

public <R> R collect(Supplier<R> supplier,
                     ObjIntConsumer<R> accumulator,
                     BiConsumer<R,R> combiner)

Specified by:

collect in interface IntStream

sum

public int sum()

Specified by:

sum in interface IntStream

min

public OptionalInt min()

Specified by:

min in interface IntStream

max

public OptionalInt max()

Specified by:

max in interface IntStream

count

public long count()

Specified by:

count in interface IntStream

average

public OptionalDouble average()

Specified by:

average in interface IntStream

summaryStatistics

public IntSummaryStatistics summaryStatistics()

Specified by:

summaryStatistics in interface IntStream

anyMatch

public boolean anyMatch(IntPredicate predicate)

Specified by:

anyMatch in interface IntStream

allMatch

public boolean allMatch(IntPredicate predicate)

Specified by:

allMatch in interface IntStream

noneMatch

public boolean noneMatch(IntPredicate predicate)

Specified by:

noneMatch in interface IntStream

findFirst

public OptionalInt findFirst()

Specified by:

findFirst in interface IntStream

findAny

public OptionalInt findAny()

Specified by:

findAny in interface IntStream

asLongStream

public LongStream asLongStream()

Specified by:

asLongStream in interface IntStream

asDoubleStream

public DoubleStream asDoubleStream()

Specified by:

asDoubleStream in interface IntStream

boxed

public Stream<Integer> boxed()

Specified by:

boxed in interface IntStream

iterator

public PrimitiveIterator.OfInt iterator()

Specified by:

iterator in interface BaseStream<Integer,IntStream>

Specified by:

iterator in interface IntStream

spliterator

public Spliterator.OfInt spliterator()

Specified by:

spliterator in interface BaseStream<Integer,IntStream>

Specified by:

spliterator in interface IntStream

isParallel

public boolean isParallel()

Specified by:

isParallel 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)