 All Superinterfaces:
AutoCloseable
,BaseStream<Double,DoubleStream>
public interface DoubleStream extends BaseStream<Double,DoubleStream>
double
primitive specialization of
Stream
.
The following example illustrates an aggregate operation using
Stream
and DoubleStream
, computing the sum of the weights of the
red widgets:
double sum = widgets.stream()
.filter(w > w.getColor() == RED)
.mapToDouble(w > w.getWeight())
.sum();
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. Since:
 1.8
 See Also:
Stream
, java.util.stream

Nested Class Summary
Nested Classes Modifier and Type Interface Description static interface
DoubleStream.Builder
A mutable builder for aDoubleStream
. 
Method Summary
Modifier and Type Method Description boolean
allMatch(DoublePredicate predicate)
Returns whether all elements of this stream match the provided predicate.boolean
anyMatch(DoublePredicate predicate)
Returns whether any elements of this stream match the provided predicate.OptionalDouble
average()
Returns anOptionalDouble
describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty.Stream<Double>
boxed()
Returns aStream
consisting of the elements of this stream, boxed toDouble
.static DoubleStream.Builder
builder()
Returns a builder for aDoubleStream
.<R> R
collect(Supplier<R> supplier, ObjDoubleConsumer<R> accumulator, BiConsumer<R,R> combiner)
Performs a mutable reduction operation on the elements of this stream.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.long
count()
Returns the count of elements in this stream.DoubleStream
distinct()
Returns a stream consisting of the distinct elements of this stream.default DoubleStream
dropWhile(DoublePredicate predicate)
Returns, if this stream is ordered, a stream consisting of the remaining elements of this stream after dropping the longest prefix of elements that match the given predicate.static DoubleStream
empty()
Returns an empty sequentialDoubleStream
.DoubleStream
filter(DoublePredicate predicate)
Returns a stream consisting of the elements of this stream that match the given predicate.OptionalDouble
findAny()
Returns anOptionalDouble
describing some element of the stream, or an emptyOptionalDouble
if the stream is empty.OptionalDouble
findFirst()
Returns anOptionalDouble
describing the first element of this stream, or an emptyOptionalDouble
if the stream is empty.DoubleStream
flatMap(DoubleFunction<? extends DoubleStream> mapper)
Returns a stream consisting of the results of replacing each element of this stream with the contents of a mapped stream produced by applying the provided mapping function to each element.void
forEach(DoubleConsumer action)
Performs an action for each element of this stream.void
forEachOrdered(DoubleConsumer action)
Performs an action for each element of this stream, guaranteeing that each element is processed in encounter order for streams that have a defined encounter order.static DoubleStream
generate(DoubleSupplier s)
Returns an infinite sequential unordered stream where each element is generated by the providedDoubleSupplier
.static DoubleStream
iterate(double seed, DoublePredicate hasNext, DoubleUnaryOperator next)
Returns a sequential orderedDoubleStream
produced by iterative application of the givennext
function to an initial element, conditioned on satisfying the givenhasNext
predicate.static DoubleStream
iterate(double seed, DoubleUnaryOperator f)
Returns an infinite sequential orderedDoubleStream
produced by iterative application of a functionf
to an initial elementseed
, producing aStream
consisting ofseed
,f(seed)
,f(f(seed))
, etc.DoubleStream
limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated to be no longer thanmaxSize
in length.DoubleStream
map(DoubleUnaryOperator mapper)
Returns a stream consisting of the results of applying the given function to the elements of this stream.IntStream
mapToInt(DoubleToIntFunction mapper)
Returns anIntStream
consisting of the results of applying the given function to the elements of this stream.LongStream
mapToLong(DoubleToLongFunction mapper)
Returns aLongStream
consisting of the results of applying the given function to the elements of this stream.<U> Stream<U>
mapToObj(DoubleFunction<? extends U> mapper)
Returns an objectvaluedStream
consisting of the results of applying the given function to the elements of this stream.OptionalDouble
max()
Returns anOptionalDouble
describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty.OptionalDouble
min()
Returns anOptionalDouble
describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty.boolean
noneMatch(DoublePredicate predicate)
Returns whether no elements of this stream match the provided predicate.static DoubleStream
of(double t)
Returns a sequentialDoubleStream
containing a single element.static DoubleStream
of(double... values)
Returns a sequential ordered stream whose elements are the specified values.DoubleStream
peek(DoubleConsumer action)
Returns a stream consisting of the elements of this stream, additionally performing the provided action on each element as elements are consumed from the resulting stream.double
reduce(double identity, DoubleBinaryOperator op)
Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value.OptionalDouble
reduce(DoubleBinaryOperator op)
Performs a reduction on the elements of this stream, using an associative accumulation function, and returns anOptionalDouble
describing the reduced value, if any.DoubleStream
skip(long n)
Returns a stream consisting of the remaining elements of this stream after discarding the firstn
elements of the stream.DoubleStream
sorted()
Returns a stream consisting of the elements of this stream in sorted order.double
sum()
Returns the sum of elements in this stream.DoubleSummaryStatistics
summaryStatistics()
Returns aDoubleSummaryStatistics
describing various summary data about the elements of this stream.default DoubleStream
takeWhile(DoublePredicate predicate)
Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate.double[]
toArray()
Returns an array containing the elements of this stream.Methods declared in interface java.util.stream.BaseStream
close, isParallel, iterator, onClose, parallel, sequential, spliterator, unordered

Method Details

filter
Returns a stream consisting of the elements of this stream that match the given predicate.This is an intermediate operation.
 Parameters:
predicate
 a noninterfering, stateless predicate to apply to each element to determine if it should be included Returns:
 the new stream

map
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
 a noninterfering, stateless function to apply to each element Returns:
 the new stream

mapToObj
Returns an objectvaluedStream
consisting of the results of applying the given function to the elements of this stream.This is an intermediate operation.
 Type Parameters:
U
 the element type of the new stream Parameters:
mapper
 a noninterfering, stateless function to apply to each element Returns:
 the new stream

mapToInt
Returns anIntStream
consisting of the results of applying the given function to the elements of this stream.This is an intermediate operation.
 Parameters:
mapper
 a noninterfering, stateless function to apply to each element Returns:
 the new stream

mapToLong
Returns aLongStream
consisting of the results of applying the given function to the elements of this stream.This is an intermediate operation.
 Parameters:
mapper
 a noninterfering, stateless function to apply to each element Returns:
 the new stream

flatMap
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 isclosed
after its contents have been placed into this stream. (If a mapped stream isnull
an empty stream is used, instead.)This is an intermediate operation.
 Parameters:
mapper
 a noninterfering, stateless function to apply to each element which produces aDoubleStream
of new values Returns:
 the new stream
 See Also:
Stream.flatMap(Function)

distinct
DoubleStream distinct()Returns a stream consisting of the distinct elements of this stream. The elements are compared for equality according toDouble.compare(double, double)
.This is a stateful intermediate operation.
 Returns:
 the result stream

sorted
DoubleStream sorted()Returns a stream consisting of the elements of this stream in sorted order. The elements are compared for equality according toDouble.compare(double, double)
.This is a stateful intermediate operation.
 Returns:
 the result stream

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

limit
Returns a stream consisting of the elements of this stream, truncated to be no longer thanmaxSize
in length. API Note:
 While
limit()
is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, especially for large values ofmaxSize
, sincelimit(n)
is constrained to return not just any n elements, but the first n elements in the encounter order. Using an unordered stream source (such asgenerate(DoubleSupplier)
) or removing the ordering constraint withBaseStream.unordered()
may result in significant speedups oflimit()
in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization withlimit()
in parallel pipelines, switching to sequential execution withBaseStream.sequential()
may improve performance.  Parameters:
maxSize
 the number of elements the stream should be limited to Returns:
 the new stream
 Throws:
IllegalArgumentException
 ifmaxSize
is negative

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

takeWhile
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).
 API Note:
 While
takeWhile()
is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such asgenerate(DoubleSupplier)
) or removing the ordering constraint withBaseStream.unordered()
may result in significant speedups oftakeWhile()
in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization withtakeWhile()
in parallel pipelines, switching to sequential execution withBaseStream.sequential()
may improve performance.  Implementation Requirements:
 The default implementation obtains the
spliterator
of this stream, wraps that spliterator so as to support the semantics of this operation on traversal, and returns a new stream associated with the wrapped spliterator. The returned stream preserves the execution characteristics of this stream (namely parallel or sequential execution as perBaseStream.isParallel()
) but the wrapped spliterator may choose to not support splitting. When the returned stream is closed, the close handlers for both the returned and this stream are invoked.  Parameters:
predicate
 a noninterfering, stateless predicate to apply to elements to determine the longest prefix of elements. Returns:
 the new stream
 Since:
 9

dropWhile
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.
 API Note:
 While
dropWhile()
is generally a cheap operation on sequential stream pipelines, it can be quite expensive on ordered parallel pipelines, since the operation is constrained to return not just any valid prefix, but the longest prefix of elements in the encounter order. Using an unordered stream source (such asgenerate(DoubleSupplier)
) or removing the ordering constraint withBaseStream.unordered()
may result in significant speedups ofdropWhile()
in parallel pipelines, if the semantics of your situation permit. If consistency with encounter order is required, and you are experiencing poor performance or memory utilization withdropWhile()
in parallel pipelines, switching to sequential execution withBaseStream.sequential()
may improve performance.  Implementation Requirements:
 The default implementation obtains the
spliterator
of this stream, wraps that spliterator so as to support the semantics of this operation on traversal, and returns a new stream associated with the wrapped spliterator. The returned stream preserves the execution characteristics of this stream (namely parallel or sequential execution as perBaseStream.isParallel()
) but the wrapped spliterator may choose to not support splitting. When the returned stream is closed, the close handlers for both the returned and this stream are invoked.  Parameters:
predicate
 a noninterfering, stateless predicate to apply to elements to determine the longest prefix of elements. Returns:
 the new stream
 Since:
 9

forEach
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
 a noninterfering action to perform on the elements

forEachOrdered
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
 a noninterfering action to perform on the elements See Also:
forEach(DoubleConsumer)

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

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

reduce
Performs a reduction on the elements of this stream, using an associative accumulation function, and returns anOptionalDouble
describing the reduced value, if any. This is equivalent to:
but is not constrained to execute sequentially.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();
The
accumulator
function must be an associative function.This is a terminal operation.
 Parameters:
op
 an associative, noninterfering, stateless function for combining two values Returns:
 the result of the reduction
 See Also:
reduce(double, DoubleBinaryOperator)

collect
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 anArrayList
, and elements are incorporated by updating the state of the result rather than by replacing the result. This produces a result equivalent to:R result = supplier.get(); for (double element : this stream) accumulator.accept(result, element); return result;
Like
reduce(double, DoubleBinaryOperator)
,collect
operations can be parallelized without requiring additional synchronization.This is a terminal operation.
 Type Parameters:
R
 the type of the mutable result container Parameters:
supplier
 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
 an associative, noninterfering, stateless function that must fold an element into a result container.combiner
 an associative, noninterfering, stateless function that accepts two partial result containers and merges them, which must be compatible with the accumulator function. The combiner function must fold the elements from the second result container into the first result container. Returns:
 the result of the reduction
 See Also:
Stream.collect(Supplier, BiConsumer, BiConsumer)

sum
double sum()Returns the sum of elements in this stream. Summation is a special case of a reduction. If floatingpoint summation were exact, this method would be equivalent to:
However, since floatingpoint summation is not exact, the above code is not necessarily equivalent to the summation computation done by this method.return reduce(0, Double::sum);
The value of a floatingpoint 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 nonfinite sum being computed. This can occur even if the all the elements being summed are finite. If any element is nonfinite, the sum will be nonfinite:
 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.
This is a terminal operation.
 API Note:
 Elements sorted by increasing absolute magnitude tend to yield more accurate results.
 Returns:
 the sum of elements in this stream

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

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

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

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

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

anyMatch
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 thenfalse
is returned and the predicate is not evaluated.This is a shortcircuiting terminal operation.
 API Note:
 This method evaluates the existential quantification of the predicate over the elements of the stream (for some x P(x)).
 Parameters:
predicate
 a noninterfering, stateless predicate to apply to elements of this stream Returns:
true
if any elements of the stream match the provided predicate, otherwisefalse

allMatch
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 thentrue
is returned and the predicate is not evaluated.This is a shortcircuiting terminal operation.
 API Note:
 This method evaluates the universal quantification of the
predicate over the elements of the stream (for all x P(x)). If the
stream is empty, the quantification is said to be vacuously
satisfied and is always
true
(regardless of P(x)).  Parameters:
predicate
 a noninterfering, stateless predicate to apply to elements of this stream Returns:
true
if either all elements of the stream match the provided predicate or the stream is empty, otherwisefalse

noneMatch
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 thentrue
is returned and the predicate is not evaluated.This is a shortcircuiting terminal operation.
 API Note:
 This method evaluates the universal quantification of the
negated predicate over the elements of the stream (for all x ~P(x)). If
the stream is empty, the quantification is said to be vacuously satisfied
and is always
true
, regardless of P(x).  Parameters:
predicate
 a noninterfering, stateless predicate to apply to elements of this stream Returns:
true
if either no elements of the stream match the provided predicate or the stream is empty, otherwisefalse

findFirst
OptionalDouble findFirst()Returns anOptionalDouble
describing the first element of this stream, or an emptyOptionalDouble
if the stream is empty. If the stream has no encounter order, then any element may be returned.This is a shortcircuiting terminal operation.
 Returns:
 an
OptionalDouble
describing the first element of this stream, or an emptyOptionalDouble
if the stream is empty

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

boxed
Returns aStream
consisting of the elements of this stream, boxed toDouble
.This is an intermediate operation.
 Returns:
 a
Stream
consistent of the elements of this stream, each boxed to aDouble

builder
Returns a builder for aDoubleStream
. Returns:
 a stream builder

empty
Returns an empty sequentialDoubleStream
. Returns:
 an empty sequential stream

of
Returns a sequentialDoubleStream
containing a single element. Parameters:
t
 the single element Returns:
 a singleton sequential stream

of
Returns a sequential ordered stream whose elements are the specified values. Parameters:
values
 the elements of the new stream Returns:
 the new stream

iterate
Returns an infinite sequential orderedDoubleStream
produced by iterative application of a functionf
to an initial elementseed
, producing aStream
consisting ofseed
,f(seed)
,f(f(seed))
, etc.The first element (position
0
) in theDoubleStream
will be the providedseed
. Forn > 0
, the element at positionn
, will be the result of applying the functionf
to the element at positionn  1
.The action of applying
f
for one element happensbefore the action of applyingf
for subsequent elements. For any given element the action may be performed in whatever thread the library chooses. Parameters:
seed
 the initial elementf
 a function to be applied to the previous element to produce a new element Returns:
 a new sequential
DoubleStream

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

generate
Returns an infinite sequential unordered stream where each element is generated by the providedDoubleSupplier
. This is suitable for generating constant streams, streams of random elements, etc. Parameters:
s
 theDoubleSupplier
for generated elements Returns:
 a new infinite sequential unordered
DoubleStream

concat
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.
 API Note:
 To preserve optimization opportunities this method binds each stream to
its source and accepts only two streams as parameters. For example, the
exact size of the concatenated stream source can be computed if the exact
size of each input stream source is known.
To concatenate more streams without binding, or without nested calls to
this method, try creating a stream of streams and flatmapping with the
identity function, for example:
DoubleStream concat = Stream.of(s1, s2, s3, s4).flatMapToDouble(s > s);
 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
.  Parameters:
a
 the first streamb
 the second stream Returns:
 the concatenation of the two input streams
