java8.util.stream

Class DoubleStreams

java.lang.Object

java8.util.stream.DoubleStreams

public final class DoubleStreams
extends Object

A place for static default implementations of the new Java 8/9 static interface methods and default interface methods (takeWhile(), dropWhile()) in the DoubleStream interface.

Method Summary

Modifier and Type	Method and Description
static DoubleStream.Builder	builder() Returns a builder for a DoubleStream.
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.
static DoubleStream	dropWhile(DoubleStream stream, DoublePredicate predicate) Returns a stream consisting of the remaining elements of the passed stream after discarding elements that match the given predicate up to, but not discarding, the first element encountered that does not match the predicate.
static DoubleStream	empty() Returns an empty sequential DoubleStream.
static DoubleStream	generate(DoubleSupplier s) Returns an infinite sequential unordered stream where each element is generated by the provided DoubleSupplier.
static DoubleStream	iterate(double seed, 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.
static DoubleStream	of(double... values) Returns a sequential ordered stream whose elements are the specified values.
static DoubleStream	of(double t) Returns a sequential DoubleStream containing a single element.
static DoubleStream	takeWhile(DoubleStream stream, DoublePredicate predicate) Returns a stream consisting of elements of the passed stream that match the given predicate up to, but discarding, the first element encountered that does not match the predicate.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

takeWhile

public static DoubleStream takeWhile(DoubleStream stream,
                                     DoublePredicate predicate)

Returns a stream consisting of elements of the passed stream that match the given predicate up to, but discarding, the first element encountered that does not match the predicate. All subsequently encountered elements are discarded.

This is a short-circuiting stateful intermediate operation.

Parameters:

stream - the stream to wrap for the takeWhile() operation

predicate - a non-interfering, predicate to apply to each element to determine if it should be included, or it and all subsequently encountered elements be discarded.

Returns:

the new stream

Since:

9

dropWhile

public static DoubleStream dropWhile(DoubleStream stream,
                                     DoublePredicate predicate)

Returns a stream consisting of the remaining elements of the passed stream after discarding elements that match the given predicate up to, but not discarding, the first element encountered that does not match the predicate. All subsequently encountered elements are not discarded.

This is a stateful intermediate operation.

Parameters:

stream - the stream to wrap for the dropWhile() operation

predicate - a non-interfering, predicate to apply to each element to determine if it should be discarded, or it and all subsequently encountered elements be included.

Returns:

the new stream

Since:

9

builder

public static DoubleStream.Builder builder()

Returns a builder for a DoubleStream.

Returns:

a stream builder

empty

public static DoubleStream empty()

Returns an empty sequential DoubleStream.

Returns:

an empty sequential stream

of

public static DoubleStream of(double t)

Returns a sequential DoubleStream containing a single element.

Parameters:

t - the single element

Returns:

a singleton sequential stream

of

public static DoubleStream of(double... values)

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

Parameters:

values - the elements of the new stream

Returns:

the new stream

iterate

public static DoubleStream iterate(double seed,
                                   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.

Parameters:

seed - the initial element

f - a function to be applied to the previous element to produce a new element

Returns:

a new sequential DoubleStream

generate

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 - the DoubleSupplier for generated elements

Returns:

a new infinite sequential unordered DoubleStream

concat

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.

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.

Subsequent changes to the sequential/parallel execution mode of the returned stream are not guaranteed to be propagated to the input streams.

Parameters:

a - the first stream

b - the second stream

Returns:

the concatenation of the two input streams