Added in API level 24

LongStream

interface LongStream : BaseStream<Long!, LongStream!>

java.util.stream.LongStream

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

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

<code>long sum = widgets.stream()
                        .filter(w -&gt; w.getColor() == RED)
                        .mapToLong(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 LongStream.
abstract	LongMapMultiConsumer Represents an operation that accepts a long-valued argument and a LongConsumer, and returns no result.

Public methods
abstract Boolean	allMatch(predicate: LongPredicate!) Returns whether all elements of this stream match the provided predicate.
abstract Boolean	anyMatch(predicate: LongPredicate!) Returns whether any elements of this stream match the provided predicate.
abstract DoubleStream!	asDoubleStream() Returns a DoubleStream consisting of the elements of this stream, converted to double.
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<Long!>!	boxed() Returns a Stream consisting of the elements of this stream, each boxed to a Long.
open static LongStream.Builder!	builder() Returns a builder for a LongStream.
abstract R	collect(supplier: Supplier<R>!, accumulator: ObjLongConsumer<R>!, combiner: BiConsumer<R, R>!) Performs a mutable reduction operation on the elements of this stream.
open static LongStream!	concat(a: LongStream!, b: LongStream!) 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 LongStream!	distinct() Returns a stream consisting of the distinct elements of this stream.
open LongStream!	dropWhile(predicate: LongPredicate!) 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 LongStream!	empty() Returns an empty sequential LongStream.
abstract LongStream!	filter(predicate: LongPredicate!) Returns a stream consisting of the elements of this stream that match the given predicate.
abstract OptionalLong!	findAny() Returns an OptionalLong describing some element of the stream, or an empty OptionalLong if the stream is empty.
abstract OptionalLong!	findFirst() Returns an OptionalLong describing the first element of this stream, or an empty OptionalLong if the stream is empty.
abstract LongStream!	flatMap(mapper: LongFunction<out LongStream!>!) 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: LongConsumer!) Performs an action for each element of this stream.
abstract Unit	forEachOrdered(action: LongConsumer!) 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 LongStream!	generate(s: LongSupplier!) Returns an infinite sequential unordered stream where each element is generated by the provided LongSupplier.
open static LongStream!	iterate(seed: Long, f: LongUnaryOperator!) Returns an infinite sequential ordered LongStream 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 LongStream!	iterate(seed: Long, hasNext: LongPredicate!, next: LongUnaryOperator!) Returns a sequential ordered LongStream produced by iterative application of the given next function to an initial element, conditioned on satisfying the given hasNext predicate.
abstract PrimitiveIterator.OfLong!	iterator()
abstract LongStream!	limit(maxSize: Long) Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length.
abstract LongStream!	map(mapper: LongUnaryOperator!) Returns a stream consisting of the results of applying the given function to the elements of this stream.
open LongStream!	mapMulti(mapper: LongStream.LongMapMultiConsumer!) Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements.
abstract DoubleStream!	mapToDouble(mapper: LongToDoubleFunction!) Returns a DoubleStream consisting of the results of applying the given function to the elements of this stream.
abstract IntStream!	mapToInt(mapper: LongToIntFunction!) Returns an IntStream consisting of the results of applying the given function to the elements of this stream.
abstract Stream<U>!	mapToObj(mapper: LongFunction<out U>!) Returns an object-valued Stream consisting of the results of applying the given function to the elements of this stream.
abstract OptionalLong!	max() Returns an OptionalLong describing the maximum element of this stream, or an empty optional if this stream is empty.
abstract OptionalLong!	min() Returns an OptionalLong describing the minimum element of this stream, or an empty optional if this stream is empty.
abstract Boolean	noneMatch(predicate: LongPredicate!) Returns whether no elements of this stream match the provided predicate.
open static LongStream!	of(t: Long) Returns a sequential LongStream containing a single element.
open static LongStream!	of(vararg values: Long) Returns a sequential ordered stream whose elements are the specified values.
abstract LongStream!	parallel()
abstract LongStream!	peek(action: LongConsumer!) 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.
open static LongStream!	range(startInclusive: Long, endExclusive: Long) Returns a sequential ordered LongStream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1.
open static LongStream!	rangeClosed(startInclusive: Long, endInclusive: Long) Returns a sequential ordered LongStream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1.
abstract Long	reduce(identity: Long, op: LongBinaryOperator!) 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 OptionalLong!	reduce(op: LongBinaryOperator!) Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalLong describing the reduced value, if any.
abstract LongStream!	sequential()
abstract LongStream!	skip(n: Long) Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream.
abstract LongStream!	sorted() Returns a stream consisting of the elements of this stream in sorted order.
abstract Spliterator.OfLong!	spliterator()
abstract Long	sum() Returns the sum of elements in this stream.
abstract LongSummaryStatistics!	summaryStatistics() Returns a LongSummaryStatistics describing various summary data about the elements of this stream.
open LongStream!	takeWhile(predicate: LongPredicate!) 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 LongArray!	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: LongPredicate!): 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	LongPredicate!: 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: LongPredicate!): 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	LongPredicate!: 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

asDoubleStream

Added in API level 24

abstract fun asDoubleStream(): DoubleStream!

Returns a DoubleStream consisting of the elements of this stream, converted to double.

This is an intermediate operation.

Return
DoubleStream!	a DoubleStream consisting of the elements of this stream, converted to double

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. This 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<Long!>!

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

This is an intermediate operation.

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

builder

Added in API level 24

open static fun builder(): LongStream.Builder!

Returns a builder for a LongStream.

Return
LongStream.Builder!	a stream builder

collect

Added in API level 24

abstract fun <R : Any!> collect(
    supplier: Supplier<R>!, 
    accumulator: ObjLongConsumer<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 (long element : this stream)
          accumulator.accept(result, element);
      return result;
  </code>

Like reduce(long,java.util.function.LongBinaryOperator), 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	ObjLongConsumer<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: LongStream!, 
    b: LongStream!
): LongStream!

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	LongStream!: the first stream
b	LongStream!: the second stream

Return
LongStream!	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 map(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(): LongStream!

Returns a stream consisting of the distinct elements of this stream.

This is a stateful intermediate operation.

Return
LongStream!	the new stream

dropWhile

Added in API level 35

open fun dropWhile(predicate: LongPredicate!): LongStream!

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

Return
LongStream!	the new stream

empty

Added in API level 24

open static fun empty(): LongStream!

Returns an empty sequential LongStream.

Return
LongStream!	an empty sequential stream

filter

Added in API level 24

abstract fun filter(predicate: LongPredicate!): LongStream!

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

This is an intermediate operation.

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

Return
LongStream!	the new stream

findAny

Added in API level 24

abstract fun findAny(): OptionalLong!

Returns an OptionalLong describing some element of the stream, or an empty OptionalLong 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
OptionalLong!	an OptionalLong describing some element of this stream, or an empty OptionalLong if the stream is empty

See Also

• #findFirst()

findFirst

Added in API level 24

abstract fun findFirst(): OptionalLong!

Returns an OptionalLong describing the first element of this stream, or an empty OptionalLong 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
OptionalLong!	an OptionalLong describing the first element of this stream, or an empty OptionalLong if the stream is empty

flatMap

Added in API level 24

abstract fun flatMap(mapper: LongFunction<out LongStream!>!): LongStream!

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

Return
LongStream!	the new stream

See Also

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

forEach

Added in API level 24

abstract fun forEach(action: LongConsumer!): 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	LongConsumer!: a non-interfering action to perform on the elements

forEachOrdered

Added in API level 24

abstract fun forEachOrdered(action: LongConsumer!): 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	LongConsumer!: a non-interfering action to perform on the elements

See Also

• #forEach(LongConsumer)

generate

Added in API level 24

open static fun generate(s: LongSupplier!): LongStream!

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

Parameters
s	LongSupplier!: the LongSupplier for generated elements

Return
LongStream!	a new infinite sequential unordered LongStream

iterate

Added in API level 24

open static fun iterate(
    seed: Long, 
    f: LongUnaryOperator!
): LongStream!

Returns an infinite sequential ordered LongStream 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 LongStream 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	Long: the initial element
f	LongUnaryOperator!: a function to be applied to the previous element to produce a new element

Return
LongStream!	a new sequential LongStream

iterate

Added in API level 35

open static fun iterate(
    seed: Long, 
    hasNext: LongPredicate!, 
    next: LongUnaryOperator!
): LongStream!

Returns a sequential ordered LongStream 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.

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

<code>for (long index=seed; hasNext.test(index); index = next.applyAsLong(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	Long: the initial element
hasNext	LongPredicate!: a predicate to apply to elements to determine when the stream must terminate.
next	LongUnaryOperator!: a function to be applied to the previous element to produce a new element

Return
LongStream!	a new sequential LongStream

iterator

Added in API level 24

abstract fun iterator(): PrimitiveIterator.OfLong!

Return
PrimitiveIterator.OfLong!	the element iterator for this stream

limit

Added in API level 24

abstract fun limit(maxSize: Long): LongStream!

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
LongStream!	the new stream

Exceptions
java.lang.IllegalArgumentException	if maxSize is negative

map

Added in API level 24

abstract fun map(mapper: LongUnaryOperator!): LongStream!

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	LongUnaryOperator!: a non-interfering, stateless function to apply to each element

Return
LongStream!	the new stream

mapMulti

Added in API level 35

open fun mapMulti(mapper: LongStream.LongMapMultiConsumer!): LongStream!

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	LongStream.LongMapMultiConsumer!: a non-interfering, stateless function that generates replacement elements

Return
LongStream!	the new stream

See Also

• java.util.stream.Stream#mapMulti

mapToDouble

Added in API level 24

abstract fun mapToDouble(mapper: LongToDoubleFunction!): DoubleStream!

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

This is an intermediate operation.

Parameters
mapper	LongToDoubleFunction!: a non-interfering, stateless function to apply to each element

Return
DoubleStream!	the new stream

mapToInt

Added in API level 24

abstract fun mapToInt(mapper: LongToIntFunction!): 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	LongToIntFunction!: a non-interfering, stateless function to apply to each element

Return
IntStream!	the new stream

mapToObj

Added in API level 24

abstract fun <U : Any!> mapToObj(mapper: LongFunction<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	LongFunction<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(): OptionalLong!

Returns an OptionalLong describing the maximum element of this stream, or an empty optional if this stream is empty. This is a special case of a reduction and is equivalent to:

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

This is a terminal operation.

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

min

Added in API level 24

abstract fun min(): OptionalLong!

Returns an OptionalLong describing the minimum element of this stream, or an empty optional if this stream is empty. This is a special case of a reduction and is equivalent to:

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

This is a terminal operation.

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

noneMatch

Added in API level 24

abstract fun noneMatch(predicate: LongPredicate!): 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	LongPredicate!: 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: Long): LongStream!

Returns a sequential LongStream containing a single element.

Parameters
t	Long: the single element

Return
LongStream!	a singleton sequential stream

of

Added in API level 24

open static fun of(vararg values: Long): LongStream!

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

Parameters
values	Long: the elements of the new stream

Return
LongStream!	the new stream

parallel

Added in API level 24

abstract fun parallel(): LongStream!

Return
LongStream!	a parallel stream

peek

Added in API level 24

abstract fun peek(action: LongConsumer!): LongStream!

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

Return
LongStream!	the new stream

range

Added in API level 24

open static fun range(
    startInclusive: Long, 
    endExclusive: Long
): LongStream!

Returns a sequential ordered LongStream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1.

Parameters
startInclusive	Long: the (inclusive) initial value
endExclusive	Long: the exclusive upper bound

Return
LongStream!	a sequential LongStream for the range of long elements

rangeClosed

Added in API level 24

open static fun rangeClosed(
    startInclusive: Long, 
    endInclusive: Long
): LongStream!

Returns a sequential ordered LongStream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1.

Parameters
startInclusive	Long: the (inclusive) initial value
endInclusive	Long: the inclusive upper bound

Return
LongStream!	a sequential LongStream for the range of long elements

reduce

Added in API level 24

abstract fun reduce(
    identity: Long, 
    op: LongBinaryOperator!
): Long

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>long result = identity;
      for (long element : this stream)
          result = accumulator.applyAsLong(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	Long: the identity value for the accumulating function
op	LongBinaryOperator!: an associative, non-interfering, stateless function for combining two values

Return
Long	the result of the reduction

See Also

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

reduce

Added in API level 24

abstract fun reduce(op: LongBinaryOperator!): OptionalLong!

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

<code>boolean foundAny = false;
      long result = null;
      for (long element : this stream) {
          if (!foundAny) {
              foundAny = true;
              result = element;
          }
          else
              result = accumulator.applyAsLong(result, element);
      }
      return foundAny ? OptionalLong.of(result) : OptionalLong.empty();
  </code>

but is not constrained to execute sequentially.

The accumulator function must be an associative function.

This is a terminal operation.

Parameters
op	LongBinaryOperator!: an associative, non-interfering, stateless function for combining two values

Return
OptionalLong!	the result of the reduction

See Also

• #reduce(long, LongBinaryOperator)

sequential

Added in API level 24

abstract fun sequential(): LongStream!

Return
LongStream!	a sequential stream

skip

Added in API level 24

abstract fun skip(n: Long): LongStream!

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
LongStream!	the new stream

Exceptions
java.lang.IllegalArgumentException	if n is negative

sorted

Added in API level 24

abstract fun sorted(): LongStream!

Returns a stream consisting of the elements of this stream in sorted order.

This is a stateful intermediate operation.

Return
LongStream!	the new stream

spliterator

Added in API level 24

abstract fun spliterator(): Spliterator.OfLong!

Return
Spliterator.OfLong!	the element spliterator for this stream

sum

Added in API level 24

abstract fun sum(): Long

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

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

This is a terminal operation.

Return
Long	the sum of elements in this stream

summaryStatistics

Added in API level 24

abstract fun summaryStatistics(): LongSummaryStatistics!

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

This is a terminal operation.

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

takeWhile

Added in API level 35

open fun takeWhile(predicate: LongPredicate!): LongStream!

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

Return
LongStream!	the new stream

toArray

Added in API level 24

abstract fun toArray(): LongArray!

Returns an array containing the elements of this stream.

This is a terminal operation.

Return
LongArray!	an array containing the elements of this stream