Added in API level 24

DoubleStream

interface DoubleStream : BaseStream<Double!, DoubleStream!>

java.util.stream.DoubleStream

A sequence of primitive double-valued elements supporting sequential and parallel aggregate operations. This is the double primitive specialization of .

The following example illustrates an aggregate operation using Stream and DoubleStream, computing the sum of the weights of the red widgets:

<code>double sum = widgets.stream()
                          .filter(w -&gt; w.getColor() == RED)
                          .mapToDouble(w -&gt; w.getWeight())
                          .sum();
  </code>

See the class documentation for Stream and the package documentation for java.util.stream for additional specification of streams, stream operations, stream pipelines, and parallelism.

Summary

Nested classes
abstract	Builder A mutable builder for a DoubleStream.
abstract	DoubleMapMultiConsumer Represents an operation that accepts a double-valued argument and a DoubleConsumer, and returns no result.

Public methods
abstract Boolean	allMatch(predicate: DoublePredicate!) Returns whether all elements of this stream match the provided predicate.
abstract Boolean	anyMatch(predicate: DoublePredicate!) Returns whether any elements of this stream match the provided predicate.
abstract OptionalDouble!	average() Returns an OptionalDouble describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty.
abstract Stream<Double!>!	boxed() Returns a Stream consisting of the elements of this stream, boxed to Double.
open static DoubleStream.Builder!	builder() Returns a builder for a DoubleStream.
abstract R	collect(supplier: Supplier<R>!, accumulator: ObjDoubleConsumer<R>!, combiner: BiConsumer<R, R>!) Performs a mutable reduction operation on the elements of this stream.
open static DoubleStream!	concat(a: DoubleStream!, b: DoubleStream!) Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream.
abstract Long	count() Returns the count of elements in this stream.
abstract DoubleStream!	distinct() Returns a stream consisting of the distinct elements of this stream.
open DoubleStream!	dropWhile(predicate: DoublePredicate!) 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.
open static DoubleStream!	empty() Returns an empty sequential DoubleStream.
abstract DoubleStream!	filter(predicate: DoublePredicate!) Returns a stream consisting of the elements of this stream that match the given predicate.
abstract OptionalDouble!	findAny() Returns an OptionalDouble describing some element of the stream, or an empty OptionalDouble if the stream is empty.
abstract OptionalDouble!	findFirst() Returns an OptionalDouble describing the first element of this stream, or an empty OptionalDouble if the stream is empty.
abstract DoubleStream!	flatMap(mapper: DoubleFunction<out DoubleStream!>!) 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.
abstract Unit	forEach(action: DoubleConsumer!) Performs an action for each element of this stream.
abstract Unit	forEachOrdered(action: DoubleConsumer!) 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.
open static DoubleStream!	generate(s: DoubleSupplier!) Returns an infinite sequential unordered stream where each element is generated by the provided DoubleSupplier.
open static DoubleStream!	iterate(seed: Double, f: DoubleUnaryOperator!) 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.
open static DoubleStream!	iterate(seed: Double, hasNext: DoublePredicate!, next: DoubleUnaryOperator!) 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.
abstract PrimitiveIterator.OfDouble!	iterator()
abstract DoubleStream!	limit(maxSize: Long) Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.
abstract DoubleStream!	map(mapper: DoubleUnaryOperator!) Returns a stream consisting of the results of applying the given function to the elements of this stream.
open DoubleStream!	mapMulti(mapper: DoubleStream.DoubleMapMultiConsumer!) Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements.
abstract IntStream!	mapToInt(mapper: DoubleToIntFunction!) Returns an IntStream consisting of the results of applying the given function to the elements of this stream.
abstract LongStream!	mapToLong(mapper: DoubleToLongFunction!) Returns a LongStream consisting of the results of applying the given function to the elements of this stream.
abstract Stream<U>!	mapToObj(mapper: DoubleFunction<out U>!) Returns an object-valued Stream consisting of the results of applying the given function to the elements of this stream.
abstract OptionalDouble!	max() Returns an OptionalDouble describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty.
abstract OptionalDouble!	min() Returns an OptionalDouble describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty.
abstract Boolean	noneMatch(predicate: DoublePredicate!) Returns whether no elements of this stream match the provided predicate.
open static DoubleStream!	of(t: Double) Returns a sequential DoubleStream containing a single element.
open static DoubleStream!	of(vararg values: Double) Returns a sequential ordered stream whose elements are the specified values.
abstract DoubleStream!	parallel()
abstract DoubleStream!	peek(action: DoubleConsumer!) 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.
abstract Double	reduce(identity: Double, op: DoubleBinaryOperator!) Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value.
abstract OptionalDouble!	reduce(op: DoubleBinaryOperator!) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalDouble describing the reduced value, if any.
abstract DoubleStream!	sequential()
abstract DoubleStream!	skip(n: Long) Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream.
abstract DoubleStream!	sorted() Returns a stream consisting of the elements of this stream in sorted order.
abstract Spliterator.OfDouble!	spliterator()
abstract Double	sum() Returns the sum of elements in this stream.
abstract DoubleSummaryStatistics!	summaryStatistics() Returns a DoubleSummaryStatistics describing various summary data about the elements of this stream.
open DoubleStream!	takeWhile(predicate: DoublePredicate!) Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate.
abstract DoubleArray!	toArray() Returns an array containing the elements of this stream.

Inherited functions

From class BaseStream Unit close() Closes this stream, causing all close handlers for this stream pipeline to be called. Boolean isParallel() Returns whether this stream, if a terminal operation were to be executed, would execute in parallel. Calling this method after invoking an terminal stream operation method may yield unpredictable results. S onClose(closeHandler: Runnable!) Returns an equivalent stream with an additional close handler. Close handlers are run when the close() method is called on the stream, and are executed in the order they were added. All close handlers are run, even if earlier close handlers throw exceptions. If any close handler throws an exception, the first exception thrown will be relayed to the caller of close(), with any remaining exceptions added to that exception as suppressed exceptions (unless one of the remaining exceptions is the same exception as the first exception, since an exception cannot suppress itself.) May return itself. This is an intermediate operation. S unordered() Returns an equivalent stream that is unordered. May return itself, either because the stream was already unordered, or because the underlying stream state was modified to be unordered. This is an intermediate operation.

Public methods

allMatch

Added in API level 24

abstract fun allMatch(predicate: DoublePredicate!): Boolean

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.

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

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

anyMatch

Added in API level 24

abstract fun anyMatch(predicate: DoublePredicate!): Boolean

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.

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

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

average

Added in API level 24

abstract fun average(): OptionalDouble!

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.

Return
OptionalDouble!	an OptionalDouble containing the average element of this stream, or an empty optional if the stream is empty

boxed

Added in API level 24

abstract fun boxed(): Stream<Double!>!

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

This is an intermediate operation.

Return
Stream<Double!>!	a Stream consistent of the elements of this stream, each boxed to a Double

builder

Added in API level 24

open static fun builder(): DoubleStream.Builder!

Returns a builder for a DoubleStream.

Return
DoubleStream.Builder!	a stream builder

collect

Added in API level 24

abstract fun <R : Any!> collect(
    supplier: Supplier<R>!, 
    accumulator: ObjDoubleConsumer<R>!, 
    combiner: BiConsumer<R, R>!
): R

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:

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

Like reduce(double,java.util.function.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.

Return
R	the result of the reduction

See Also

• java.util.stream.Stream#collect(Supplier, BiConsumer, BiConsumer)

concat

Added in API level 24

open static fun concat(
    a: DoubleStream!, 
    b: DoubleStream!
): DoubleStream!

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.

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

Return
DoubleStream!	the concatenation of the two input streams

count

Added in API level 24

abstract fun count(): Long

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

<code>return mapToLong(e -&gt; 1L).sum();
  </code>

This is a terminal operation.

Return
Long	the count of elements in this stream

distinct

Added in API level 24

abstract fun distinct(): DoubleStream!

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.

Return
DoubleStream!	the result stream

dropWhile

Added in API level 35

open fun dropWhile(predicate: DoublePredicate!): DoubleStream!

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.

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

Return
DoubleStream!	the new stream

empty

Added in API level 24

open static fun empty(): DoubleStream!

Returns an empty sequential DoubleStream.

Return
DoubleStream!	an empty sequential stream

filter

Added in API level 24

abstract fun filter(predicate: DoublePredicate!): DoubleStream!

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

Return
DoubleStream!	the new stream

findAny

Added in API level 24

abstract fun findAny(): OptionalDouble!

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.)

Return
OptionalDouble!	an OptionalDouble describing some element of this stream, or an empty OptionalDouble if the stream is empty

See Also

• #findFirst()

findFirst

Added in API level 24

abstract fun findFirst(): OptionalDouble!

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.

Return
OptionalDouble!	an OptionalDouble describing the first element of this stream, or an empty OptionalDouble if the stream is empty

flatMap

Added in API level 24

abstract fun flatMap(mapper: DoubleFunction<out DoubleStream!>!): DoubleStream!

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<out DoubleStream!>!: a non-interfering, stateless function to apply to each element which produces a DoubleStream of new values

Return
DoubleStream!	the new stream

See Also

• java.util.stream.Stream#flatMap(Function)

forEach

Added in API level 24

abstract fun forEach(action: DoubleConsumer!): Unit

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

Added in API level 24

abstract fun forEachOrdered(action: DoubleConsumer!): Unit

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

Added in API level 24

open static fun generate(s: DoubleSupplier!): DoubleStream!

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

Return
DoubleStream!	a new infinite sequential unordered DoubleStream

iterate

Added in API level 24

open static fun iterate(
    seed: Double, 
    f: DoubleUnaryOperator!
): DoubleStream!

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

Return
DoubleStream!	a new sequential DoubleStream

iterate

Added in API level 35

open static fun iterate(
    seed: Double, 
    hasNext: DoublePredicate!, 
    next: DoubleUnaryOperator!
): DoubleStream!

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:

<code>for (double index=seed; hasNext.test(index); index = next.applyAsDouble(index)) {
          ...
      }
  </code>

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

Return
DoubleStream!	a new sequential DoubleStream

iterator

Added in API level 24

abstract fun iterator(): PrimitiveIterator.OfDouble!

Return
PrimitiveIterator.OfDouble!	the element iterator for this stream

limit

Added in API level 24

abstract fun limit(maxSize: Long): DoubleStream!

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.

Parameters
maxSize	Long: the number of elements the stream should be limited to

Return
DoubleStream!	the new stream

Exceptions
java.lang.IllegalArgumentException	if maxSize is negative

map

Added in API level 24

abstract fun map(mapper: DoubleUnaryOperator!): DoubleStream!

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

Return
DoubleStream!	the new stream

mapMulti

Added in API level 35

open fun mapMulti(mapper: DoubleStream.DoubleMapMultiConsumer!): DoubleStream!

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.

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

Return
DoubleStream!	the new stream

See Also

• java.util.stream.Stream#mapMulti

mapToInt

Added in API level 24

abstract fun mapToInt(mapper: DoubleToIntFunction!): IntStream!

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

Return
IntStream!	the new stream

mapToLong

Added in API level 24

abstract fun mapToLong(mapper: DoubleToLongFunction!): LongStream!

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

Return
LongStream!	the new stream

mapToObj

Added in API level 24

abstract fun <U : Any!> mapToObj(mapper: DoubleFunction<out U>!): Stream<U>!

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<out U>!: a non-interfering, stateless function to apply to each element

Return
Stream<U>!	the new stream

max

Added in API level 24

abstract fun max(): OptionalDouble!

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:

<code>return reduce(Double::max);
  </code>

This is a terminal operation.

Return
OptionalDouble!	an OptionalDouble containing the maximum element of this stream, or an empty optional if the stream is empty

min

Added in API level 24

abstract fun min(): OptionalDouble!

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:

<code>return reduce(Double::min);
  </code>

This is a terminal operation.

Return
OptionalDouble!	an OptionalDouble containing the minimum element of this stream, or an empty optional if the stream is empty

noneMatch

Added in API level 24

abstract fun noneMatch(predicate: DoublePredicate!): Boolean

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.

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

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

of

Added in API level 24

open static fun of(t: Double): DoubleStream!

Returns a sequential DoubleStream containing a single element.

Parameters
t	Double: the single element

Return
DoubleStream!	a singleton sequential stream

of

Added in API level 24

open static fun of(vararg values: Double): DoubleStream!

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

Parameters
values	Double: the elements of the new stream

Return
DoubleStream!	the new stream

parallel

Added in API level 24

abstract fun parallel(): DoubleStream!

Return
DoubleStream!	a parallel stream

peek

Added in API level 24

abstract fun peek(action: DoubleConsumer!): DoubleStream!

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.

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

Return
DoubleStream!	the new stream

reduce

Added in API level 24

abstract fun reduce(
    identity: Double, 
    op: DoubleBinaryOperator!
): Double

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:

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

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.

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

Return
Double	the result of the reduction

See Also

• #sum()
• #min()
• #max()
• #average()

reduce

Added in API level 24

abstract fun reduce(op: DoubleBinaryOperator!): OptionalDouble!

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:

<code>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();
  </code>

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

Return
OptionalDouble!	the result of the reduction

See Also

• #reduce(double, DoubleBinaryOperator)

sequential

Added in API level 24

abstract fun sequential(): DoubleStream!

Return
DoubleStream!	a sequential stream

skip

Added in API level 24

abstract fun skip(n: Long): DoubleStream!

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.

Parameters
n	Long: the number of leading elements to skip

Return
DoubleStream!	the new stream

Exceptions
java.lang.IllegalArgumentException	if n is negative

sorted

Added in API level 24

abstract fun sorted(): DoubleStream!

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.

Return
DoubleStream!	the result stream

spliterator

Added in API level 24

abstract fun spliterator(): Spliterator.OfDouble!

Return
Spliterator.OfDouble!	the element spliterator for this stream

sum

Added in API level 24

abstract fun sum(): Double

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:

<code>return reduce(0, Double::sum);
  </code>

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.

Return
Double	the sum of elements in this stream

summaryStatistics

Added in API level 24

abstract fun summaryStatistics(): DoubleSummaryStatistics!

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.

Return
DoubleSummaryStatistics!	a DoubleSummaryStatistics describing various summary data about the elements of this stream

takeWhile

Added in API level 35

open fun takeWhile(predicate: DoublePredicate!): DoubleStream!

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.

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

Return
DoubleStream!	the new stream

toArray

Added in API level 24

abstract fun toArray(): DoubleArray!

Returns an array containing the elements of this stream.

This is a terminal operation.

Return
DoubleArray!	an array containing the elements of this stream