LongStream

See also:

• Stream
• java.util.stream

allMatch

 public abstract boolean allMatch (LongPredicate 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.

anyMatch

 public abstract boolean anyMatch (LongPredicate 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.

asDoubleStream

 public abstract DoubleStream asDoubleStream ()

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

This is an intermediate operation.

average

 public abstract OptionalDouble average ()

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.

boxed

 public abstract Stream<Long> boxed ()

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

This is an intermediate operation.

builder

 public static LongStream.Builder builder ()

Returns a builder for a LongStream.

collect

 public abstract R collect (Supplier<R> supplier, ObjLongConsumer<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 (long element : this stream) accumulator.accept(result, element); return result; 

Like reduce(long, java.util.function.LongBinaryOperator), collect operations can be parallelized without requiring additional synchronization.

This is a terminal operation.

concat

 public static LongStream concat (LongStream a, LongStream 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.

count

 public abstract long count ()

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

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

This is a terminal operation.

distinct

 public abstract LongStream distinct ()

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

This is a stateful intermediate operation.

dropWhile

 public LongStream dropWhile (LongPredicate 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.

empty

 public static LongStream empty ()

Returns an empty sequential LongStream.

filter

 public abstract LongStream filter (LongPredicate predicate)

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

This is an intermediate operation.

findAny

 public abstract OptionalLong findAny ()

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.)

findFirst

 public abstract OptionalLong findFirst ()

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.

flatMap

 public abstract LongStream flatMap (LongFunction<? extends LongStream> 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.

forEach

 public abstract void forEach (LongConsumer 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.

forEachOrdered

 public abstract void forEachOrdered (LongConsumer 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.

generate

 public static LongStream generate (LongSupplier s)

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.

iterate

 public static LongStream iterate (long seed, LongPredicate hasNext, LongUnaryOperator next)

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:

for (long index=seed; hasNext.test(index); index = next.applyAsLong(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.

iterate

 public static LongStream iterate (long seed, LongUnaryOperator f)

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.

iterator

 public abstract PrimitiveIterator.OfLong iterator ()

Returns an iterator for the elements of this stream.

This is a terminal operation.

limit

 public abstract LongStream 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.

map

 public abstract LongStream map (LongUnaryOperator mapper)

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

This is an intermediate operation.

mapMulti

 public LongStream mapMulti (LongStream.LongMapMultiConsumer 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.

mapToDouble

 public abstract DoubleStream mapToDouble (LongToDoubleFunction mapper)

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

This is an intermediate operation.

mapToInt

 public abstract IntStream mapToInt (LongToIntFunction mapper)

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

This is an intermediate operation.

mapToObj

 public abstract Stream<U> mapToObj (LongFunction<? 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.

max

 public abstract OptionalLong max ()

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:

return reduce(Long::max); 

This is a terminal operation.

min

 public abstract OptionalLong min ()

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:

return reduce(Long::min); 

This is a terminal operation.

noneMatch

 public abstract boolean noneMatch (LongPredicate 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.

of

 public static LongStream of (long t)

Returns a sequential LongStream containing a single element.

of

 public static LongStream of (long... values)

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

parallel

 public abstract LongStream 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.

peek

 public abstract LongStream peek (LongConsumer 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.

range

 public static LongStream range (long startInclusive, long endExclusive)

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

rangeClosed

 public static LongStream rangeClosed (long startInclusive, long endInclusive)

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

reduce

 public abstract OptionalLong reduce (LongBinaryOperator op)

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:

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(); 

The accumulator function must be an associative function.

This is a terminal operation.

reduce

 public abstract long reduce (long identity, LongBinaryOperator 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:

long result = identity; for (long element : this stream) result = accumulator.applyAsLong(result, element) return result; 

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.

sequential

 public abstract LongStream 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.

skip

 public abstract LongStream 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.

sorted

 public abstract LongStream sorted ()

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

This is a stateful intermediate operation.

spliterator

 public abstract Spliterator.OfLong spliterator ()

Returns a spliterator for the elements of this stream.

This is a terminal operation.

sum

 public abstract long sum ()

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

return reduce(0, Long::sum); 

This is a terminal operation.

summaryStatistics

 public abstract LongSummaryStatistics summaryStatistics ()

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.

takeWhile

 public LongStream takeWhile (LongPredicate 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.

toArray

 public abstract long[] toArray ()

Returns an array containing the elements of this stream.

This is a terminal operation.