OpenJDK 27 · java.util.stream.DoubleStream · APIdia, the JavaDoc alternative

Modifier and Type	Class and Description
public static interface	DoubleStream.Builder A mutable builder for a `DoubleStream`.
public static interface	DoubleStream.DoubleMapMultiConsumer Represents an operation that accepts a `double`-valued argument and a DoubleConsumer, and returns no result.

Method Summary

Modifier and Type	Method and Description
public boolean	Returns: `true` if either all elements of the stream match the provided predicate or the stream is empty, otherwise `false` allMatch(DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream predicate) Returns whether all elements of this stream match the provided predicate.
public boolean	Returns: `true` if any elements of the stream match the provided predicate, otherwise `false` anyMatch(DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream predicate) Returns whether any elements of this stream match the provided predicate.
public OptionalDouble	Returns: an `OptionalDouble` containing the average element of this stream, or an empty optional if the stream is empty average() Returns an `OptionalDouble` describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty.
public Stream<Double>	Returns: a `Stream` consistent of the elements of this stream, each boxed to a `Double` boxed() Returns a `Stream` consisting of the elements of this stream, boxed to `Double`.
public static DoubleStream.Builder	Returns: a stream builder builder() Returns a builder for a `DoubleStream`.
public < the type of the mutable result container R> R	Returns: the result of the reduction collect(Supplier<R> a function that creates a new mutable result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time. supplier, ObjDoubleConsumer<R> an associative, non-interfering, stateless function that must fold an element into a result container. accumulator, BiConsumer<R, R> an associative, non-interfering, stateless function that accepts two partial result containers and merges them, which must be compatible with the accumulator function. The combiner function must fold the elements from the second result container into the first result container. combiner) Performs a mutable reduction operation on the elements of this stream.
public static DoubleStream	Returns: the concatenation of the two input streams concat(DoubleStream the first stream a, DoubleStream the second stream b) Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
public long	Returns: the count of elements in this stream count() Returns the count of elements in this stream.
public DoubleStream	Returns: the result stream distinct() Returns a stream consisting of the distinct elements of this stream.
public default DoubleStream	Returns: the new stream dropWhile(DoublePredicate a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements. predicate) Returns, if this stream is ordered, a stream consisting of the remaining elements of this stream after dropping the longest prefix of elements that match the given predicate.
public static DoubleStream	Returns: an empty sequential stream empty() Returns an empty sequential `DoubleStream`.
public DoubleStream	Returns: the new stream filter(DoublePredicate a non-interfering, stateless predicate to apply to each element to determine if it should be included predicate) Returns a stream consisting of the elements of this stream that match the given predicate.
public OptionalDouble	Returns: an `OptionalDouble` describing some element of this stream, or an empty `OptionalDouble` if the stream is empty findAny() Returns an `OptionalDouble` describing some element of the stream, or an empty `OptionalDouble` if the stream is empty.
public OptionalDouble	Returns: an `OptionalDouble` describing the first element of this stream, or an empty `OptionalDouble` if the stream is empty findFirst() Returns an `OptionalDouble` describing the first element of this stream, or an empty `OptionalDouble` if the stream is empty.
public DoubleStream	Returns: the new stream flatMap(DoubleFunction<? extends DoubleStream> a non-interfering, stateless function to apply to each element which produces a `DoubleStream` of new values mapper) Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element.
public void	forEach(DoubleConsumer a non-interfering action to perform on the elements action) Performs an action for each element of this stream.
public void	forEachOrdered(DoubleConsumer a non-interfering action to perform on the elements action) Performs an action for each element of this stream, guaranteeing that each element is processed in encounter order for streams that have a defined encounter order.
public static DoubleStream	Returns: a new infinite sequential unordered `DoubleStream` generate(DoubleSupplier the `DoubleSupplier` for generated elements s) Returns an infinite sequential unordered stream where each element is generated by the provided `DoubleSupplier`.
public static DoubleStream	Returns: a new sequential `DoubleStream` iterate(final double the initial element seed, final DoubleUnaryOperator a function to be applied to the previous element to produce a new element f) Returns an infinite sequential ordered `DoubleStream` produced by iterative application of a function `f` to an initial element `seed`, producing a `Stream` consisting of `seed`, `f(seed)`, `f(f(seed))`, etc. The first element (position `0`) in the `DoubleStream` will be the provided `seed`.
public static DoubleStream	Returns: a new sequential `DoubleStream` iterate(double the initial element seed, DoublePredicate a predicate to apply to elements to determine when the stream must terminate. hasNext, DoubleUnaryOperator a function to be applied to the previous element to produce a new element next) Returns a sequential ordered `DoubleStream` produced by iterative application of the given `next` function to an initial element, conditioned on satisfying the given `hasNext` predicate.
public PrimitiveIterator.OfDouble	iterator() Redeclares java.util.stream.BaseStream.iterator. Returns an iterator for the elements of this stream.
public DoubleStream	Returns: the new stream limit(long the number of elements the stream should be limited to maxSize) Returns a stream consisting of the elements of this stream, truncated to be no longer than `maxSize` in length.
public DoubleStream	Returns: the new stream map(DoubleUnaryOperator a non-interfering, stateless function to apply to each element mapper) Returns a stream consisting of the results of applying the given function to the elements of this stream.
public default DoubleStream	Returns: the new stream mapMulti(DoubleStream.DoubleMapMultiConsumer a non-interfering, stateless function that generates replacement elements mapper) Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements.
public IntStream	Returns: the new stream mapToInt(DoubleToIntFunction a non-interfering, stateless function to apply to each element mapper) Returns an `IntStream` consisting of the results of applying the given function to the elements of this stream.
public LongStream	Returns: the new stream mapToLong(DoubleToLongFunction a non-interfering, stateless function to apply to each element mapper) Returns a `LongStream` consisting of the results of applying the given function to the elements of this stream.
public < the element type of the new stream U> Stream<U>	Returns: the new stream mapToObj(DoubleFunction<? extends U> a non-interfering, stateless function to apply to each element mapper) Returns an object-valued `Stream` consisting of the results of applying the given function to the elements of this stream.
public OptionalDouble	Returns: an `OptionalDouble` containing the maximum element of this stream, or an empty optional if the stream is empty max() Returns an `OptionalDouble` describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty.
public OptionalDouble	Returns: an `OptionalDouble` containing the minimum element of this stream, or an empty optional if the stream is empty min() Returns an `OptionalDouble` describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty.
public boolean	Returns: `true` if either no elements of the stream match the provided predicate or the stream is empty, otherwise `false` noneMatch(DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream predicate) Returns whether no elements of this stream match the provided predicate.
public static DoubleStream	Returns: a singleton sequential stream of(double the single element t) Returns a sequential `DoubleStream` containing a single element.
public static DoubleStream	Returns: the new stream of(double... the elements of the new stream values) Returns a sequential ordered stream whose elements are the specified values.
public DoubleStream	parallel() Redeclares java.util.stream.BaseStream.parallel. Returns an equivalent stream that is parallel.
public DoubleStream	Returns: the new stream peek(DoubleConsumer a non-interfering action to perform on the elements as they are consumed from the stream action) Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.
public double	Returns: the result of the reduction reduce(double the identity value for the accumulating function identity, DoubleBinaryOperator an associative, non-interfering, stateless function for combining two values op) Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value.
public OptionalDouble	Returns: the result of the reduction reduce(DoubleBinaryOperator an associative, non-interfering, stateless function for combining two values op) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an `OptionalDouble` describing the reduced value, if any.
public DoubleStream	sequential() Redeclares java.util.stream.BaseStream.sequential. Returns an equivalent stream that is sequential.
public DoubleStream	Returns: the new stream skip(long the number of leading elements to skip n) Returns a stream consisting of the remaining elements of this stream after discarding the first `n` elements of the stream.
public DoubleStream	Returns: the result stream sorted() Returns a stream consisting of the elements of this stream in sorted order.
public Spliterator.OfDouble	spliterator() Redeclares java.util.stream.BaseStream.spliterator. Returns a spliterator for the elements of this stream.
public double	Returns: the sum of elements in this stream sum() Returns the sum of elements in this stream.
public DoubleSummaryStatistics	Returns: a `DoubleSummaryStatistics` describing various summary data about the elements of this stream summaryStatistics() Returns a `DoubleSummaryStatistics` describing various summary data about the elements of this stream.
public default DoubleStream	Returns: the new stream takeWhile(DoublePredicate a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements. predicate) Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate.
public double[]	Returns: an array containing the elements of this stream toArray() Returns an array containing the elements of this stream.

Inherited from java.util.stream.BaseStream:: close isParallel onClose unordered

Method Detail

allMatch back to summary

allMatch	back to summary
public boolean allMatch(DoublePredicate predicate) Returns whether all elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then `true` is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. API Note This method evaluates the universal quantification of the predicate over the elements of the stream (for all x P(x)). If the stream is empty, the quantification is said to be vacuously satisfied and is always `true` (regardless of P(x)). Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream Returns:boolean `true` if either all elements of the stream match the provided predicate or the stream is empty, otherwise `false`

public boolean allMatch(DoublePredicate predicate)

Returns whether all elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated.

This is a short-circuiting terminal operation.

API Note

This method evaluates the universal quantification of the predicate over the elements of the stream (for all x P(x)). If the stream is empty, the quantification is said to be vacuously satisfied and is always true (regardless of P(x)).

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to elements of this stream

Returns:boolean

true if either all elements of the stream match the provided predicate or the stream is empty, otherwise false

anyMatch back to summary

anyMatch	back to summary
public boolean anyMatch(DoublePredicate predicate) Returns whether any elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then `false` is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. API Note This method evaluates the existential quantification of the predicate over the elements of the stream (for some x P(x)). Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream Returns:boolean `true` if any elements of the stream match the provided predicate, otherwise `false`

public boolean anyMatch(DoublePredicate predicate)

Returns whether any elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then false is returned and the predicate is not evaluated.

This is a short-circuiting terminal operation.

API Note

This method evaluates the existential quantification of the predicate over the elements of the stream (for some x P(x)).

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to elements of this stream

Returns:boolean

true if any elements of the stream match the provided predicate, otherwise false

average back to summary

average	back to summary
public OptionalDouble average() Returns an `OptionalDouble` describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty. The computed average can vary numerically and have the special case behavior as computing the sum; see `sum` for details. The average is a special case of a reduction. This is a terminal operation. API Note Elements sorted by increasing absolute magnitude tend to yield more accurate results. Returns:OptionalDouble an `OptionalDouble` containing the average element of this stream, or an empty optional if the stream is empty

public OptionalDouble average()

Returns an OptionalDouble describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty.

The computed average can vary numerically and have the special case behavior as computing the sum; see sum for details.

The average is a special case of a reduction.

This is a terminal operation.

API Note

Elements sorted by increasing absolute magnitude tend to yield more accurate results.

Returns:OptionalDouble: an OptionalDouble containing the average element of this stream, or an empty optional if the stream is empty

boxed back to summary

boxed	back to summary
public Stream<Double> boxed() Returns a `Stream` consisting of the elements of this stream, boxed to `Double`. This is an intermediate operation. Returns:Stream<Double> a `Stream` consistent of the elements of this stream, each boxed to a `Double`

public Stream<Double> boxed()

Returns a Stream consisting of the elements of this stream, boxed to Double.

This is an intermediate operation.

Returns:Stream<Double>: a Stream consistent of the elements of this stream, each boxed to a Double

builder back to summary

builder	back to summary
public static DoubleStream.Builder builder() Returns a builder for a `DoubleStream`. Returns:DoubleStream.Builder a stream builder

public static DoubleStream.Builder builder()

Returns a builder for a DoubleStream.

Returns:DoubleStream.Builder: a stream builder

collect back to summary

collect	back to summary
public <R> R collect(Supplier<R> supplier, ObjDoubleConsumer<R> accumulator, BiConsumer<R, R> combiner) Performs a mutable reduction operation on the elements of this stream. A mutable reduction is one in which the reduced value is a mutable result container, such as an `ArrayList`, and elements are incorporated by updating the state of the result rather than by replacing the result. This produces a result equivalent to: `R result = supplier.get(); for (double element : this stream) accumulator.accept(result, element); return result;` Like `reduce(double, DoubleBinaryOperator)`, `collect` operations can be parallelized without requiring additional synchronization. This is a terminal operation. Parameters <R> the type of the mutable result container supplier:Supplier<R> a function that creates a new mutable result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time. accumulator:ObjDoubleConsumer<R> an associative, non-interfering, stateless function that must fold an element into a result container. combiner:BiConsumer<R, R> an associative, non-interfering, stateless function that accepts two partial result containers and merges them, which must be compatible with the accumulator function. The combiner function must fold the elements from the second result container into the first result container. Returns:R the result of the reduction See Also `Stream#collect(Supplier, BiConsumer, BiConsumer)`

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

Performs a mutable reduction operation on the elements of this stream. A mutable reduction is one in which the reduced value is a mutable result container, such as an ArrayList, and elements are incorporated by updating the state of the result rather than by replacing the result. This produces a result equivalent to:

R result = supplier.get();
    for (double element : this stream)
        accumulator.accept(result, element);
    return result;

Like reduce(double, DoubleBinaryOperator), collect operations can be parallelized without requiring additional synchronization.

This is a terminal operation.

Parameters

<R>: the type of the mutable result container
supplier:Supplier<R>: a function that creates a new mutable result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time.
accumulator:ObjDoubleConsumer<R>: an associative, non-interfering, stateless function that must fold an element into a result container.
combiner:BiConsumer<R, R>: an associative, non-interfering, stateless function that accepts two partial result containers and merges them, which must be compatible with the accumulator function. The combiner function must fold the elements from the second result container into the first result container.

Returns:R

the result of the reduction

concat back to summary

concat	back to summary
public static DoubleStream concat(DoubleStream a, DoubleStream b) Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream. The resulting stream is ordered if both of the input streams are ordered, and parallel if either of the input streams is parallel. When the resulting stream is closed, the close handlers for both input streams are invoked. This method operates on the two input streams and binds each stream to its source. As a result subsequent modifications to an input stream source may not be reflected in the concatenated stream result. Implementation Note Use caution when constructing streams from repeated concatenation. Accessing an element of a deeply concatenated stream can result in deep call chains, or even `StackOverflowError`. API Note To preserve optimization opportunities this method binds each stream to its source and accepts only two streams as parameters. For example, the exact size of the concatenated stream source can be computed if the exact size of each input stream source is known. To concatenate more streams without binding, or without nested calls to this method, try creating a stream of streams and flat-mapping with the identity function, for example: `DoubleStream concat = Stream.of(s1, s2, s3, s4).flatMapToDouble(s -> s);` Parameters a:DoubleStream the first stream b:DoubleStream the second stream Returns:DoubleStream the concatenation of the two input streams

public static DoubleStream concat(DoubleStream a, DoubleStream b)

Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream. The resulting stream is ordered if both of the input streams are ordered, and parallel if either of the input streams is parallel. When the resulting stream is closed, the close handlers for both input streams are invoked.

This method operates on the two input streams and binds each stream to its source. As a result subsequent modifications to an input stream source may not be reflected in the concatenated stream result.

Implementation Note

Use caution when constructing streams from repeated concatenation. Accessing an element of a deeply concatenated stream can result in deep call chains, or even StackOverflowError.

API Note

To preserve optimization opportunities this method binds each stream to its source and accepts only two streams as parameters. For example, the exact size of the concatenated stream source can be computed if the exact size of each input stream source is known. To concatenate more streams without binding, or without nested calls to this method, try creating a stream of streams and flat-mapping with the identity function, for example:

DoubleStream concat = Stream.of(s1, s2, s3, s4).flatMapToDouble(s -> s);

Parameters

a:DoubleStream: the first stream
b:DoubleStream: the second stream

Returns:DoubleStream

the concatenation of the two input streams

count back to summary

count	back to summary
public long count() Returns the count of elements in this stream. This is a special case of a reduction and is equivalent to: `return mapToLong(e -> 1L).sum();` This is a terminal operation. API Note An implementation may choose to not execute the stream pipeline (either sequentially or in parallel) if it is capable of computing the count directly from the stream source. In such cases no source elements will be traversed and no intermediate operations will be evaluated. Behavioral parameters with side-effects, which are strongly discouraged except for harmless cases such as debugging, may be affected. For example, consider the following stream: `DoubleStream s = DoubleStream.of(1, 2, 3, 4); long count = s.peek(System.out::println).count();` The number of elements covered by the stream source is known and the intermediate operation, `peek`, does not inject into or remove elements from the stream (as may be the case for `flatMap` or `filter` operations). Thus the count is 4 and there is no need to execute the pipeline and, as a side-effect, print out the elements. Returns:long the count of elements in this stream

public long count()

Returns the count of elements in this stream. This is a special case of a reduction and is equivalent to:

return mapToLong(e -> 1L).sum();

This is a terminal operation.

API Note

An implementation may choose to not execute the stream pipeline (either sequentially or in parallel) if it is capable of computing the count directly from the stream source. In such cases no source elements will be traversed and no intermediate operations will be evaluated. Behavioral parameters with side-effects, which are strongly discouraged except for harmless cases such as debugging, may be affected. For example, consider the following stream:

DoubleStream s = DoubleStream.of(1, 2, 3, 4);
    long count = s.peek(System.out::println).count();

The number of elements covered by the stream source is known and the intermediate operation, peek, does not inject into or remove elements from the stream (as may be the case for flatMap or filter operations). Thus the count is 4 and there is no need to execute the pipeline and, as a side-effect, print out the elements.

Returns:long: the count of elements in this stream

distinct back to summary

distinct	back to summary
public DoubleStream distinct() Returns a stream consisting of the distinct elements of this stream. The elements are compared for equality according to `java.lang.Double#compare(double, double)`. This is a stateful intermediate operation. Returns:DoubleStream the result stream

public DoubleStream distinct()

Returns a stream consisting of the distinct elements of this stream. The elements are compared for equality according to java.lang.Double#compare(double, double).

This is a stateful intermediate operation.

Returns:DoubleStream: the result stream

dropWhile back to summary

dropWhile	back to summary
public default DoubleStream dropWhile(DoublePredicate predicate) Returns, if this stream is ordered, a stream consisting of the remaining elements of this stream after dropping the longest prefix of elements that match the given predicate. Otherwise returns, if this stream is unordered, a stream consisting of the remaining elements of this stream after dropping a subset of elements that match the given predicate. If this stream is ordered then the longest prefix is a contiguous sequence of elements of this stream that match the given predicate. The first element of the sequence is the first element of this stream, and the element immediately following the last element of the sequence does not match the given predicate. If this stream is unordered, and some (but not all) elements of this stream match the given predicate, then the behavior of this operation is nondeterministic; it is free to drop any subset of matching elements (which includes the empty set). Independent of whether this stream is ordered or unordered if all elements of this stream match the given predicate then this operation drops all elements (the result is an empty stream), or if no elements of the stream match the given predicate then no elements are dropped (the result is the same as the input). This is a stateful intermediate operation. Implementation Specification The default implementation obtains the `spliterator` of this stream, wraps that spliterator so as to support the semantics of this operation on traversal, and returns a new stream associated with the wrapped spliterator. The returned stream preserves the execution characteristics of this stream (namely parallel or sequential execution as per `isParallel()`) but the wrapped spliterator may choose to not support splitting. When the returned stream is closed, the close handlers for both the returned and this stream are invoked. API Note While `dropWhile()` is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such as `generate(DoubleSupplier)`) or removing the ordering constraint with `unordered()` may result in significant speedups of `dropWhile()` in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with `dropWhile()` in parallel pipelines, switching to sequential execution with `sequential()` may improve performance. Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements. Returns:DoubleStream the new stream Since 9

public default DoubleStream dropWhile(DoublePredicate predicate)

Returns, if this stream is ordered, a stream consisting of the remaining elements of this stream after dropping the longest prefix of elements that match the given predicate. Otherwise returns, if this stream is unordered, a stream consisting of the remaining elements of this stream after dropping a subset of elements that match the given predicate.

If this stream is ordered then the longest prefix is a contiguous sequence of elements of this stream that match the given predicate. The first element of the sequence is the first element of this stream, and the element immediately following the last element of the sequence does not match the given predicate.

If this stream is unordered, and some (but not all) elements of this stream match the given predicate, then the behavior of this operation is nondeterministic; it is free to drop any subset of matching elements (which includes the empty set).

Independent of whether this stream is ordered or unordered if all elements of this stream match the given predicate then this operation drops all elements (the result is an empty stream), or if no elements of the stream match the given predicate then no elements are dropped (the result is the same as the input).

This is a stateful intermediate operation.

Implementation Specification

The default implementation obtains the spliterator of this stream, wraps that spliterator so as to support the semantics of this operation on traversal, and returns a new stream associated with the wrapped spliterator. The returned stream preserves the execution characteristics of this stream (namely parallel or sequential execution as per isParallel()) but the wrapped spliterator may choose to not support splitting. When the returned stream is closed, the close handlers for both the returned and this stream are invoked.

API Note

While dropWhile() is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such as generate(DoubleSupplier)) or removing the ordering constraint with unordered() may result in significant speedups of dropWhile() in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with dropWhile() in parallel pipelines, switching to sequential execution with sequential() may improve performance.

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements.

Returns:DoubleStream

the new stream

Since

empty back to summary

empty	back to summary
public static DoubleStream empty() Returns an empty sequential `DoubleStream`. Returns:DoubleStream an empty sequential stream

public static DoubleStream empty()

Returns an empty sequential DoubleStream.

Returns:DoubleStream: an empty sequential stream

filter	back to summary
public DoubleStream filter(DoublePredicate predicate) Returns a stream consisting of the elements of this stream that match the given predicate. This is an intermediate operation. Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to each element to determine if it should be included Returns:DoubleStream the new stream

filter

back to summary

public DoubleStream filter(DoublePredicate predicate)

Returns a stream consisting of the elements of this stream that match the given predicate.

This is an intermediate operation.

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to each element to determine if it should be included

Returns:DoubleStream

the new stream

findAny back to summary

findAny	back to summary
public OptionalDouble findAny() Returns an `OptionalDouble` describing some element of the stream, or an empty `OptionalDouble` if the stream is empty. This is a short-circuiting terminal operation. The behavior of this operation is explicitly nondeterministic; it is free to select any element in the stream. This is to allow for maximal performance in parallel operations; the cost is that multiple invocations on the same source may not return the same result. (If a stable result is desired, use `findFirst()` instead.) Returns:OptionalDouble an `OptionalDouble` describing some element of this stream, or an empty `OptionalDouble` if the stream is empty See Also `findFirst()`

public OptionalDouble findAny()

Returns an OptionalDouble describing some element of the stream, or an empty OptionalDouble if the stream is empty.

This is a short-circuiting terminal operation.

The behavior of this operation is explicitly nondeterministic; it is free to select any element in the stream. This is to allow for maximal performance in parallel operations; the cost is that multiple invocations on the same source may not return the same result. (If a stable result is desired, use findFirst() instead.)

Returns:OptionalDouble: an OptionalDouble describing some element of this stream, or an empty OptionalDouble if the stream is empty
See Also: findFirst()

findFirst back to summary

findFirst	back to summary
public OptionalDouble findFirst() Returns an `OptionalDouble` describing the first element of this stream, or an empty `OptionalDouble` if the stream is empty. If the stream has no encounter order, then any element may be returned. This is a short-circuiting terminal operation. Returns:OptionalDouble an `OptionalDouble` describing the first element of this stream, or an empty `OptionalDouble` if the stream is empty

public OptionalDouble findFirst()

Returns an OptionalDouble describing the first element of this stream, or an empty OptionalDouble if the stream is empty. If the stream has no encounter order, then any element may be returned.

This is a short-circuiting terminal operation.

Returns:OptionalDouble: an OptionalDouble describing the first element of this stream, or an empty OptionalDouble if the stream is empty

flatMap back to summary

flatMap	back to summary
public DoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper) Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is `closed` after its contents have been placed into this stream. (If a mapped stream is `null` an empty stream is used, instead.) This is an intermediate operation. Parameters mapper:DoubleFunction<? extends DoubleStream> a non-interfering, stateless function to apply to each element which produces a `DoubleStream` of new values Returns:DoubleStream the new stream See Also `Stream#flatMap(Function)`

public DoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper)

Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element. Each mapped stream is closed after its contents have been placed into this stream. (If a mapped stream is null an empty stream is used, instead.)

This is an intermediate operation.

Parameters

mapper:DoubleFunction<? extends DoubleStream>: a non-interfering, stateless function to apply to each element which produces a DoubleStream of new values

Returns:DoubleStream

the new stream

See Also

Stream#flatMap(Function)

forEach	back to summary
public void forEach(DoubleConsumer action) Performs an action for each element of this stream. This is a terminal operation. For parallel stream pipelines, this operation does not guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of parallelism. For any given element, the action may be performed at whatever time and in whatever thread the library chooses. If the action accesses shared state, it is responsible for providing the required synchronization. Parameters action:DoubleConsumer a non-interfering action to perform on the elements

forEach

back to summary

public void forEach(DoubleConsumer action)

Performs an action for each element of this stream.

This is a terminal operation.

For parallel stream pipelines, this operation does not guarantee to respect the encounter order of the stream, as doing so would sacrifice the benefit of parallelism. For any given element, the action may be performed at whatever time and in whatever thread the library chooses. If the action accesses shared state, it is responsible for providing the required synchronization.

Parameters

action:DoubleConsumer: a non-interfering action to perform on the elements

forEachOrdered back to summary

forEachOrdered	back to summary
public void forEachOrdered(DoubleConsumer action) Performs an action for each element of this stream, guaranteeing that each element is processed in encounter order for streams that have a defined encounter order. This is a terminal operation. Parameters action:DoubleConsumer a non-interfering action to perform on the elements See Also `forEach(DoubleConsumer)`

public void forEachOrdered(DoubleConsumer action)

Performs an action for each element of this stream, guaranteeing that each element is processed in encounter order for streams that have a defined encounter order.

This is a terminal operation.

Parameters

action:DoubleConsumer: a non-interfering action to perform on the elements

See Also

forEach(DoubleConsumer)

generate back to summary

generate	back to summary
public static DoubleStream generate(DoubleSupplier s) Returns an infinite sequential unordered stream where each element is generated by the provided `DoubleSupplier`. This is suitable for generating constant streams, streams of random elements, etc. Parameters s:DoubleSupplier the `DoubleSupplier` for generated elements Returns:DoubleStream a new infinite sequential unordered `DoubleStream`

public static DoubleStream generate(DoubleSupplier s)

Returns an infinite sequential unordered stream where each element is generated by the provided DoubleSupplier. This is suitable for generating constant streams, streams of random elements, etc.

Parameters

s:DoubleSupplier: the DoubleSupplier for generated elements

Returns:DoubleStream

a new infinite sequential unordered DoubleStream

iterate back to summary

iterate	back to summary
public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f) Returns an infinite sequential ordered `DoubleStream` produced by iterative application of a function `f` to an initial element `seed`, producing a `Stream` consisting of `seed`, `f(seed)`, `f(f(seed))`, etc. The first element (position `0`) in the `DoubleStream` will be the provided `seed`. For `n > 0`, the element at position `n`, will be the result of applying the function `f` to the element at position `n - 1`. The action of applying `f` for one element happens-before the action of applying `f` for subsequent elements. For any given element the action may be performed in whatever thread the library chooses. Parameters seed:double the initial element f:DoubleUnaryOperator a function to be applied to the previous element to produce a new element Returns:DoubleStream a new sequential `DoubleStream`

public static DoubleStream iterate(final double seed, final DoubleUnaryOperator f)

Returns an infinite sequential ordered DoubleStream produced by iterative application of a function f to an initial element seed, producing a Stream consisting of seed, f(seed), f(f(seed)), etc.

The first element (position 0) in the DoubleStream will be the provided seed. For n > 0, the element at position n, will be the result of applying the function f to the element at position n - 1.

The action of applying f for one element happens-before the action of applying f for subsequent elements. For any given element the action may be performed in whatever thread the library chooses.

Parameters

seed:double: the initial element
f:DoubleUnaryOperator: a function to be applied to the previous element to produce a new element

Returns:DoubleStream

a new sequential DoubleStream

iterate back to summary

iterate	back to summary
public static DoubleStream iterate(double seed, DoublePredicate hasNext, DoubleUnaryOperator next) Returns a sequential ordered `DoubleStream` produced by iterative application of the given `next` function to an initial element, conditioned on satisfying the given `hasNext` predicate. The stream terminates as soon as the `hasNext` predicate returns false. `DoubleStream.iterate` should produce the same sequence of elements as produced by the corresponding for-loop: `for (double index=seed; hasNext.test(index); index = next.applyAsDouble(index)) { ... }` The resulting sequence may be empty if the `hasNext` predicate does not hold on the seed value. Otherwise the first element will be the supplied `seed` value, the next element (if present) will be the result of applying the `next` function to the `seed` value, and so on iteratively until the `hasNext` predicate indicates that the stream should terminate. The action of applying the `hasNext` predicate to an element happens-before the action of applying the `next` function to that element. The action of applying the `next` function for one element happens-before the action of applying the `hasNext` predicate for subsequent elements. For any given element an action may be performed in whatever thread the library chooses. Parameters seed:double the initial element hasNext:DoublePredicate a predicate to apply to elements to determine when the stream must terminate. next:DoubleUnaryOperator a function to be applied to the previous element to produce a new element Returns:DoubleStream a new sequential `DoubleStream` Since 9

public static DoubleStream iterate(double seed, DoublePredicate hasNext, DoubleUnaryOperator next)

Returns a sequential ordered DoubleStream produced by iterative application of the given next function to an initial element, conditioned on satisfying the given hasNext predicate. The stream terminates as soon as the hasNext predicate returns false.

DoubleStream.iterate should produce the same sequence of elements as produced by the corresponding for-loop:

for (double index=seed; hasNext.test(index); index = next.applyAsDouble(index)) {
        ...
    }

The resulting sequence may be empty if the hasNext predicate does not hold on the seed value. Otherwise the first element will be the supplied seed value, the next element (if present) will be the result of applying the next function to the seed value, and so on iteratively until the hasNext predicate indicates that the stream should terminate.

The action of applying the hasNext predicate to an element happens-before the action of applying the next function to that element. The action of applying the next function for one element happens-before the action of applying the hasNext predicate for subsequent elements. For any given element an action may be performed in whatever thread the library chooses.

Parameters

seed:double: the initial element
hasNext:DoublePredicate: a predicate to apply to elements to determine when the stream must terminate.
next:DoubleUnaryOperator: a function to be applied to the previous element to produce a new element

Returns:DoubleStream

a new sequential DoubleStream

Since

iterator	back to summary
public PrimitiveIterator.OfDouble iterator() Redeclares java.util.stream.BaseStream.iterator. Doc from java.util.stream.BaseStream.iterator. Returns an iterator for the elements of this stream. This is a terminal operation. Annotations @Override

iterator

back to summary

public PrimitiveIterator.OfDouble iterator()

Redeclares java.util.stream.BaseStream.iterator.

Doc from java.util.stream.BaseStream.iterator.

Returns an iterator for the elements of this stream.

This is a terminal operation.

Annotations

@Override

limit back to summary

limit	back to summary
public DoubleStream limit(long maxSize) Returns a stream consisting of the elements of this stream, truncated to be no longer than `maxSize` in length. This is a short-circuiting stateful intermediate operation. API Note While `limit()` is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, especially for large values of `maxSize`, since `limit(n)` is constrained to return not just any n elements, but the first n elements in the encounter order. Using an unordered stream source (such as `generate(DoubleSupplier)`) or removing the ordering constraint with `unordered()` may result in significant speedups of `limit()` in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with `limit()` in parallel pipelines, switching to sequential execution with `sequential()` may improve performance. Parameters maxSize:long the number of elements the stream should be limited to Returns:DoubleStream the new stream Exceptions IllegalArgumentException: if `maxSize` is negative

public DoubleStream limit(long maxSize)

Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.

This is a short-circuiting stateful intermediate operation.

API Note

While limit() is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, especially for large values of maxSize, since limit(n) is constrained to return not just any n elements, but the first n elements in the encounter order. Using an unordered stream source (such as generate(DoubleSupplier)) or removing the ordering constraint with unordered() may result in significant speedups of limit() in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with limit() in parallel pipelines, switching to sequential execution with sequential() may improve performance.

Parameters

maxSize:long: the number of elements the stream should be limited to

Returns:DoubleStream

the new stream

Exceptions

IllegalArgumentException:: if maxSize is negative

map	back to summary
public DoubleStream map(DoubleUnaryOperator mapper) Returns a stream consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. Parameters mapper:DoubleUnaryOperator a non-interfering, stateless function to apply to each element Returns:DoubleStream the new stream

map

back to summary

public DoubleStream map(DoubleUnaryOperator mapper)

Returns a stream consisting of the results of applying the given function to the elements of this stream.

This is an intermediate operation.

Parameters

mapper:DoubleUnaryOperator: a non-interfering, stateless function to apply to each element

Returns:DoubleStream

the new stream

mapMulti back to summary

mapMulti	back to summary
public default DoubleStream mapMulti(DoubleStream.DoubleMapMultiConsumer mapper) Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements. Replacement is performed by applying the provided mapping function to each element in conjunction with a consumer argument that accepts replacement elements. The mapping function calls the consumer zero or more times to provide the replacement elements. This is an intermediate operation. If the consumer argument is used outside the scope of its application to the mapping function, the results are undefined. Implementation Specification The default implementation invokes `flatMap` on this stream, passing a function that behaves as follows. First, it calls the mapper function with a `DoubleConsumer` that accumulates replacement elements into a newly created internal buffer. When the mapper function returns, it creates a `DoubleStream` from the internal buffer. Finally, it returns this stream to `flatMap`. Parameters mapper:DoubleStream.DoubleMapMultiConsumer a non-interfering, stateless function that generates replacement elements Returns:DoubleStream the new stream Since 16 See Also `Stream.mapMulti`

public default DoubleStream mapMulti(DoubleStream.DoubleMapMultiConsumer mapper)

Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements. Replacement is performed by applying the provided mapping function to each element in conjunction with a consumer argument that accepts replacement elements. The mapping function calls the consumer zero or more times to provide the replacement elements.

This is an intermediate operation.

If the consumer argument is used outside the scope of its application to the mapping function, the results are undefined.

Implementation Specification

The default implementation invokes flatMap on this stream, passing a function that behaves as follows. First, it calls the mapper function with a DoubleConsumer that accumulates replacement elements into a newly created internal buffer. When the mapper function returns, it creates a DoubleStream from the internal buffer. Finally, it returns this stream to flatMap.

Parameters

mapper:DoubleStream.DoubleMapMultiConsumer: a non-interfering, stateless function that generates replacement elements

Returns:DoubleStream

the new stream

Since

See Also

Stream.mapMulti

mapToInt back to summary

mapToInt	back to summary
public IntStream mapToInt(DoubleToIntFunction mapper) Returns an `IntStream` consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. Parameters mapper:DoubleToIntFunction a non-interfering, stateless function to apply to each element Returns:IntStream the new stream

public IntStream mapToInt(DoubleToIntFunction mapper)

Returns an IntStream consisting of the results of applying the given function to the elements of this stream.

This is an intermediate operation.

Parameters

mapper:DoubleToIntFunction: a non-interfering, stateless function to apply to each element

Returns:IntStream

the new stream

mapToLong back to summary

mapToLong	back to summary
public LongStream mapToLong(DoubleToLongFunction mapper) Returns a `LongStream` consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. Parameters mapper:DoubleToLongFunction a non-interfering, stateless function to apply to each element Returns:LongStream the new stream

public LongStream mapToLong(DoubleToLongFunction mapper)

Returns a LongStream consisting of the results of applying the given function to the elements of this stream.

This is an intermediate operation.

Parameters

mapper:DoubleToLongFunction: a non-interfering, stateless function to apply to each element

Returns:LongStream

the new stream

mapToObj back to summary

mapToObj	back to summary
public <U> Stream<U> mapToObj(DoubleFunction<? extends U> mapper) Returns an object-valued `Stream` consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation. Parameters <U> the element type of the new stream mapper:DoubleFunction<? extends U> a non-interfering, stateless function to apply to each element Returns:Stream<U> the new stream

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

Returns an object-valued Stream consisting of the results of applying the given function to the elements of this stream.

This is an intermediate operation.

Parameters

<U>: the element type of the new stream
mapper:DoubleFunction<? extends U>: a non-interfering, stateless function to apply to each element

Returns:Stream<U>

the new stream

max back to summary

max	back to summary
public OptionalDouble max() Returns an `OptionalDouble` describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty. The maximum element will be `Double.NaN` if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to: `return reduce(Double::max);` This is a terminal operation. Returns:OptionalDouble an `OptionalDouble` containing the maximum element of this stream, or an empty optional if the stream is empty

public OptionalDouble max()

Returns an OptionalDouble describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty. The maximum element will be Double.NaN if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to:

return reduce(Double::max);

This is a terminal operation.

Returns:OptionalDouble: an OptionalDouble containing the maximum element of this stream, or an empty optional if the stream is empty

min back to summary

min	back to summary
public OptionalDouble min() Returns an `OptionalDouble` describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty. The minimum element will be `Double.NaN` if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to: `return reduce(Double::min);` This is a terminal operation. Returns:OptionalDouble an `OptionalDouble` containing the minimum element of this stream, or an empty optional if the stream is empty

public OptionalDouble min()

Returns an OptionalDouble describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty. The minimum element will be Double.NaN if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to:

return reduce(Double::min);

This is a terminal operation.

Returns:OptionalDouble: an OptionalDouble containing the minimum element of this stream, or an empty optional if the stream is empty

noneMatch back to summary

noneMatch	back to summary
public boolean noneMatch(DoublePredicate predicate) Returns whether no elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then `true` is returned and the predicate is not evaluated. This is a short-circuiting terminal operation. API Note This method evaluates the universal quantification of the negated predicate over the elements of the stream (for all x ~P(x)). If the stream is empty, the quantification is said to be vacuously satisfied and is always `true`, regardless of P(x). Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to elements of this stream Returns:boolean `true` if either no elements of the stream match the provided predicate or the stream is empty, otherwise `false`

public boolean noneMatch(DoublePredicate predicate)

Returns whether no elements of this stream match the provided predicate. May not evaluate the predicate on all elements if not necessary for determining the result. If the stream is empty then true is returned and the predicate is not evaluated.

This is a short-circuiting terminal operation.

API Note

This method evaluates the universal quantification of the negated predicate over the elements of the stream (for all x ~P(x)). If the stream is empty, the quantification is said to be vacuously satisfied and is always true, regardless of P(x).

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to elements of this stream

Returns:boolean

true if either no elements of the stream match the provided predicate or the stream is empty, otherwise false

of back to summary

of	back to summary
public static DoubleStream of(double t) Returns a sequential `DoubleStream` containing a single element. Parameters t:double the single element Returns:DoubleStream a singleton sequential stream

public static DoubleStream of(double t)

Returns a sequential DoubleStream containing a single element.

Parameters

t:double: the single element

Returns:DoubleStream

a singleton sequential stream

of	back to summary
public static DoubleStream of(double... values) Returns a sequential ordered stream whose elements are the specified values. Parameters values:double[] the elements of the new stream Returns:DoubleStream the new stream

back to summary

public static DoubleStream of(double... values)

Returns a sequential ordered stream whose elements are the specified values.

Parameters

values:double[]: the elements of the new stream

Returns:DoubleStream

the new stream

parallel	back to summary
public DoubleStream parallel() Redeclares java.util.stream.BaseStream.parallel. Doc from java.util.stream.BaseStream.parallel. Returns an equivalent stream that is parallel. May return itself, either because the stream was already parallel, or because the underlying stream state was modified to be parallel. This is an intermediate operation. Annotations @Override

parallel

back to summary

public DoubleStream parallel()

Redeclares java.util.stream.BaseStream.parallel.

Doc from java.util.stream.BaseStream.parallel.

Returns an equivalent stream that is parallel. May return itself, either because the stream was already parallel, or because the underlying stream state was modified to be parallel.

This is an intermediate operation.

Annotations

@Override

peek back to summary

peek	back to summary
public DoubleStream peek(DoubleConsumer action) Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream. This is an intermediate operation. For parallel stream pipelines, the action may be called at whatever time and in whatever thread the element is made available by the upstream operation. If the action modifies shared state, it is responsible for providing the required synchronization. API Note This method exists mainly to support debugging, where you want to see the elements as they flow past a certain point in a pipeline: `DoubleStream.of(1, 2, 3, 4) .filter(e -> e > 2) .peek(e -> System.out.println("Filtered value: " + e)) .map(e -> e * e) .peek(e -> System.out.println("Mapped value: " + e)) .sum();` In cases where the stream implementation is able to optimize away the production of some or all the elements (such as with short-circuiting operations like `findFirst`, or in the example described in `count`), the action will not be invoked for those elements. Parameters action:DoubleConsumer a non-interfering action to perform on the elements as they are consumed from the stream Returns:DoubleStream the new stream

public DoubleStream peek(DoubleConsumer action)

Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.

This is an intermediate operation.

For parallel stream pipelines, the action may be called at whatever time and in whatever thread the element is made available by the upstream operation. If the action modifies shared state, it is responsible for providing the required synchronization.

API Note

This method exists mainly to support debugging, where you want to see the elements as they flow past a certain point in a pipeline:

DoubleStream.of(1, 2, 3, 4)
        .filter(e -> e > 2)
        .peek(e -> System.out.println("Filtered value: " + e))
        .map(e -> e * e)
        .peek(e -> System.out.println("Mapped value: " + e))
        .sum();

In cases where the stream implementation is able to optimize away the production of some or all the elements (such as with short-circuiting operations like findFirst, or in the example described in count), the action will not be invoked for those elements.

Parameters

action:DoubleConsumer: a non-interfering action to perform on the elements as they are consumed from the stream

Returns:DoubleStream

the new stream

reduce back to summary

reduce	back to summary
public double reduce(double identity, DoubleBinaryOperator op) Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value. This is equivalent to: `double result = identity; for (double element : this stream) result = accumulator.applyAsDouble(result, element) return result;` but is not constrained to execute sequentially. The `identity` value must be an identity for the accumulator function. This means that for all `x`, `accumulator.apply(identity, x)` is equal to `x`. The `accumulator` function must be an associative function. This is a terminal operation. API Note Sum, min, max, and average are all special cases of reduction. Summing a stream of numbers can be expressed as: `double sum = numbers.reduce(0, (a, b) -> a+b);` or more compactly: `double sum = numbers.reduce(0, Double::sum);` While this may seem a more roundabout way to perform an aggregation compared to simply mutating a running total in a loop, reduction operations parallelize more gracefully, without needing additional synchronization and with greatly reduced risk of data races. Parameters identity:double the identity value for the accumulating function op:DoubleBinaryOperator an associative, non-interfering, stateless function for combining two values Returns:double the result of the reduction See Also `sum()`, `min()`, `max()`, `average()`

public double reduce(double identity, DoubleBinaryOperator op)

Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value. This is equivalent to:

double result = identity;
    for (double element : this stream)
        result = accumulator.applyAsDouble(result, element)
    return result;

but is not constrained to execute sequentially.

The identity value must be an identity for the accumulator function. This means that for all x, accumulator.apply(identity, x) is equal to x. The accumulator function must be an associative function.

This is a terminal operation.

API Note

Sum, min, max, and average are all special cases of reduction. Summing a stream of numbers can be expressed as:

double sum = numbers.reduce(0, (a, b) -> a+b);

or more compactly:

double sum = numbers.reduce(0, Double::sum);

While this may seem a more roundabout way to perform an aggregation compared to simply mutating a running total in a loop, reduction operations parallelize more gracefully, without needing additional synchronization and with greatly reduced risk of data races.

Parameters

identity:double: the identity value for the accumulating function
op:DoubleBinaryOperator: an associative, non-interfering, stateless function for combining two values

Returns:double

the result of the reduction

See Also

sum(), min(), max(), average()

reduce back to summary

reduce	back to summary
public OptionalDouble reduce(DoubleBinaryOperator op) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an `OptionalDouble` describing the reduced value, if any. This is equivalent to: `boolean foundAny = false; double result = null; for (double element : this stream) { if (!foundAny) { foundAny = true; result = element; } else result = accumulator.applyAsDouble(result, element); } return foundAny ? OptionalDouble.of(result) : OptionalDouble.empty();` but is not constrained to execute sequentially. The `accumulator` function must be an associative function. This is a terminal operation. Parameters op:DoubleBinaryOperator an associative, non-interfering, stateless function for combining two values Returns:OptionalDouble the result of the reduction See Also `reduce(double, DoubleBinaryOperator)`

public OptionalDouble reduce(DoubleBinaryOperator op)

Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalDouble describing the reduced value, if any. This is equivalent to:

boolean foundAny = false;
    double result = null;
    for (double element : this stream) {
        if (!foundAny) {
            foundAny = true;
            result = element;
        }
        else
            result = accumulator.applyAsDouble(result, element);
    }
    return foundAny ? OptionalDouble.of(result) : OptionalDouble.empty();

but is not constrained to execute sequentially.

The accumulator function must be an associative function.

This is a terminal operation.

Parameters

op:DoubleBinaryOperator: an associative, non-interfering, stateless function for combining two values

Returns:OptionalDouble

the result of the reduction

See Also

reduce(double, DoubleBinaryOperator)

sequential	back to summary
public DoubleStream sequential() Redeclares java.util.stream.BaseStream.sequential. Doc from java.util.stream.BaseStream.sequential. Returns an equivalent stream that is sequential. May return itself, either because the stream was already sequential, or because the underlying stream state was modified to be sequential. This is an intermediate operation. Annotations @Override

sequential

back to summary

public DoubleStream sequential()

Redeclares java.util.stream.BaseStream.sequential.

Doc from java.util.stream.BaseStream.sequential.

Returns an equivalent stream that is sequential. May return itself, either because the stream was already sequential, or because the underlying stream state was modified to be sequential.

This is an intermediate operation.

Annotations

@Override

skip back to summary

skip	back to summary
public DoubleStream skip(long n) Returns a stream consisting of the remaining elements of this stream after discarding the first `n` elements of the stream. If this stream contains fewer than `n` elements then an empty stream will be returned. This is a stateful intermediate operation. API Note While `skip()` is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, especially for large values of `n`, since `skip(n)` is constrained to skip not just any n elements, but the first n elements in the encounter order. Using an unordered stream source (such as `generate(DoubleSupplier)`) or removing the ordering constraint with `unordered()` may result in significant speedups of `skip()` in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with `skip()` in parallel pipelines, switching to sequential execution with `sequential()` may improve performance. Parameters n:long the number of leading elements to skip Returns:DoubleStream the new stream Exceptions IllegalArgumentException: if `n` is negative

public DoubleStream skip(long n)

Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream. If this stream contains fewer than n elements then an empty stream will be returned.

This is a stateful intermediate operation.

API Note

While skip() is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, especially for large values of n, since skip(n) is constrained to skip not just any n elements, but the first n elements in the encounter order. Using an unordered stream source (such as generate(DoubleSupplier)) or removing the ordering constraint with unordered() may result in significant speedups of skip() in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with skip() in parallel pipelines, switching to sequential execution with sequential() may improve performance.

Parameters

n:long: the number of leading elements to skip

Returns:DoubleStream

the new stream

Exceptions

IllegalArgumentException:: if n is negative

sorted back to summary

sorted	back to summary
public DoubleStream sorted() Returns a stream consisting of the elements of this stream in sorted order. The elements are compared for equality according to `java.lang.Double#compare(double, double)`. This is a stateful intermediate operation. Returns:DoubleStream the result stream

public DoubleStream sorted()

Returns a stream consisting of the elements of this stream in sorted order. The elements are compared for equality according to java.lang.Double#compare(double, double).

This is a stateful intermediate operation.

Returns:DoubleStream: the result stream

spliterator	back to summary
public Spliterator.OfDouble spliterator() Redeclares java.util.stream.BaseStream.spliterator. Doc from java.util.stream.BaseStream.spliterator. Returns a spliterator for the elements of this stream. This is a terminal operation. Annotations @Override

spliterator

back to summary

public Spliterator.OfDouble spliterator()

Redeclares java.util.stream.BaseStream.spliterator.

Doc from java.util.stream.BaseStream.spliterator.

Returns a spliterator for the elements of this stream.

This is a terminal operation.

Annotations

@Override

sum back to summary

sum	back to summary
public double sum() Returns the sum of elements in this stream. Summation is a special case of a reduction. If floating-point summation were exact, this method would be equivalent to: `return reduce(0, Double::sum);` However, since floating-point summation is not exact, the above code is not necessarily equivalent to the summation computation done by this method. The value of a floating-point sum is a function both of the input values as well as the order of addition operations. The order of addition operations of this method is intentionally not defined to allow for implementation flexibility to improve the speed and accuracy of the computed result. In particular, this method may be implemented using compensated summation or other technique to reduce the error bound in the numerical sum compared to a simple summation of `double` values. Because of the unspecified order of operations and the possibility of using differing summation schemes, the output of this method may vary on the same input elements. Various conditions can result in a non-finite sum being computed. This can occur even if the all the elements being summed are finite. If any element is non-finite, the sum will be non-finite: If any element is a NaN, then the final sum will be NaN. If the elements contain one or more infinities, the sum will be infinite or NaN. If the elements contain infinities of opposite sign, the sum will be NaN. If the elements contain infinities of one sign and an intermediate sum overflows to an infinity of the opposite sign, the sum may be NaN. It is possible for intermediate sums of finite values to overflow into opposite-signed infinities; if that occurs, the final sum will be NaN even if the elements are all finite. If all the elements are zero, the sign of zero is not guaranteed to be preserved in the final sum. This is a terminal operation. API Note Elements sorted by increasing absolute magnitude tend to yield more accurate results. Returns:double the sum of elements in this stream

public double sum()

Returns the sum of elements in this stream. Summation is a special case of a reduction. If floating-point summation were exact, this method would be equivalent to:

return reduce(0, Double::sum);

However, since floating-point summation is not exact, the above code is not necessarily equivalent to the summation computation done by this method.

The value of a floating-point sum is a function both of the input values as well as the order of addition operations. The order of addition operations of this method is intentionally not defined to allow for implementation flexibility to improve the speed and accuracy of the computed result. In particular, this method may be implemented using compensated summation or other technique to reduce the error bound in the numerical sum compared to a simple summation of double values. Because of the unspecified order of operations and the possibility of using differing summation schemes, the output of this method may vary on the same input elements.

Various conditions can result in a non-finite sum being computed. This can occur even if the all the elements being summed are finite. If any element is non-finite, the sum will be non-finite:

If any element is a NaN, then the final sum will be NaN.
If the elements contain one or more infinities, the sum will be infinite or NaN.
- If the elements contain infinities of opposite sign, the sum will be NaN.
- If the elements contain infinities of one sign and an intermediate sum overflows to an infinity of the opposite sign, the sum may be NaN.

It is possible for intermediate sums of finite values to overflow into opposite-signed infinities; if that occurs, the final sum will be NaN even if the elements are all finite. If all the elements are zero, the sign of zero is not guaranteed to be preserved in the final sum.

This is a terminal operation.

API Note

Elements sorted by increasing absolute magnitude tend to yield more accurate results.

Returns:double: the sum of elements in this stream

summaryStatistics back to summary

summaryStatistics	back to summary
public DoubleSummaryStatistics summaryStatistics() Returns a `DoubleSummaryStatistics` describing various summary data about the elements of this stream. This is a special case of a reduction. This is a terminal operation. Returns:DoubleSummaryStatistics a `DoubleSummaryStatistics` describing various summary data about the elements of this stream

public DoubleSummaryStatistics summaryStatistics()

Returns a DoubleSummaryStatistics describing various summary data about the elements of this stream. This is a special case of a reduction.

This is a terminal operation.

Returns:DoubleSummaryStatistics: a DoubleSummaryStatistics describing various summary data about the elements of this stream

takeWhile back to summary

takeWhile	back to summary
public default DoubleStream takeWhile(DoublePredicate predicate) Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate. Otherwise returns, if this stream is unordered, a stream consisting of a subset of elements taken from this stream that match the given predicate. If this stream is ordered then the longest prefix is a contiguous sequence of elements of this stream that match the given predicate. The first element of the sequence is the first element of this stream, and the element immediately following the last element of the sequence does not match the given predicate. If this stream is unordered, and some (but not all) elements of this stream match the given predicate, then the behavior of this operation is nondeterministic; it is free to take any subset of matching elements (which includes the empty set). Independent of whether this stream is ordered or unordered if all elements of this stream match the given predicate then this operation takes all elements (the result is the same as the input), or if no elements of the stream match the given predicate then no elements are taken (the result is an empty stream). This is a short-circuiting stateful intermediate operation. Implementation Specification The default implementation obtains the `spliterator` of this stream, wraps that spliterator so as to support the semantics of this operation on traversal, and returns a new stream associated with the wrapped spliterator. The returned stream preserves the execution characteristics of this stream (namely parallel or sequential execution as per `isParallel()`) but the wrapped spliterator may choose to not support splitting. When the returned stream is closed, the close handlers for both the returned and this stream are invoked. API Note While `takeWhile()` is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such as `generate(DoubleSupplier)`) or removing the ordering constraint with `unordered()` may result in significant speedups of `takeWhile()` in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with `takeWhile()` in parallel pipelines, switching to sequential execution with `sequential()` may improve performance. Parameters predicate:DoublePredicate a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements. Returns:DoubleStream the new stream Since 9

public default DoubleStream takeWhile(DoublePredicate predicate)

Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate. Otherwise returns, if this stream is unordered, a stream consisting of a subset of elements taken from this stream that match the given predicate.

If this stream is unordered, and some (but not all) elements of this stream match the given predicate, then the behavior of this operation is nondeterministic; it is free to take any subset of matching elements (which includes the empty set).

Independent of whether this stream is ordered or unordered if all elements of this stream match the given predicate then this operation takes all elements (the result is the same as the input), or if no elements of the stream match the given predicate then no elements are taken (the result is an empty stream).

This is a short-circuiting stateful intermediate operation.

Implementation Specification

API Note

While takeWhile() is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such as generate(DoubleSupplier)) or removing the ordering constraint with unordered() may result in significant speedups of takeWhile() in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization with takeWhile() in parallel pipelines, switching to sequential execution with sequential() may improve performance.

Parameters

predicate:DoublePredicate: a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements.

Returns:DoubleStream

the new stream

Since

toArray	back to summary
public double[] toArray() Returns an array containing the elements of this stream. This is a terminal operation. Returns:double[] an array containing the elements of this stream

toArray

back to summary

public double[] toArray()

Returns an array containing the elements of this stream.

This is a terminal operation.

Returns:double[]: an array containing the elements of this stream

public Interface DoubleStream

Nested and Inner Type Summary

Method Summary

Method Detail

public Interface DoubleStream.Builder

Method Summary

Method Detail

public Interface DoubleStream.DoubleMapMultiConsumer

Method Summary

Method Detail

Modifier and Type	Method and Description
public void	accept(double t) Redeclares java.util.function.DoubleConsumer.accept. Adds an element to the stream being built.
public default DoubleStream.Builder	Returns: `this` builder add(double the element to add t) Adds an element to the stream being built.
public DoubleStream	Returns: the built stream build() Builds the stream, transitioning this builder to the built state.