Interface DoubleStream
 All Superinterfaces:

AutoCloseable
,BaseStream<Double,DoubleStream>
public interface DoubleStream extends BaseStream<Double,DoubleStream>
A sequence of primitive doublevalued elements supporting sequential and parallel aggregate operations. This is the 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
Modifier and Type  Interface  Description 

static interface  DoubleStream.Builder  A mutable builder for a 
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 an 
Stream<Double>  boxed()  Returns a 
static DoubleStream.Builder  builder()  Returns a builder for a 
<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 sequential 
DoubleStream  filter(DoublePredicate predicate)  Returns a stream consisting of the elements of this stream that match the given predicate. 
OptionalDouble  findAny()  Returns an 
OptionalDouble  findFirst()  Returns an 
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 provided 
static DoubleStream  iterate(double seed,
DoublePredicate hasNext,
DoubleUnaryOperator next)  Returns a sequential ordered 
static DoubleStream  iterate(double seed,
DoubleUnaryOperator f)  Returns an infinite sequential ordered 
DoubleStream  limit(long maxSize)  Returns a stream consisting of the elements of this stream, truncated to be no longer than 
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 an 
LongStream  mapToLong(DoubleToLongFunction mapper)  Returns a 
<U> Stream<U>  mapToObj(DoubleFunction<? extends U> mapper)  Returns an objectvalued 
OptionalDouble  max()  Returns an 
OptionalDouble  min()  Returns an 
boolean  noneMatch(DoublePredicate predicate)  Returns whether no elements of this stream match the provided predicate. 
static DoubleStream  of(double t)  Returns a sequential 
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 an 
DoubleStream  skip(long n)  Returns a stream consisting of the remaining elements of this stream after discarding the first 
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 a 
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 Detail
filter
DoubleStream filter(DoublePredicate predicate)
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
DoubleStream map(DoubleUnaryOperator mapper)
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
<U> Stream<U> mapToObj(DoubleFunction<? extends U> mapper)
Returns an objectvalued Stream
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
IntStream mapToInt(DoubleToIntFunction mapper)
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
 a noninterfering, stateless function to apply to each element  Returns:
 the new stream
mapToLong
LongStream mapToLong(DoubleToLongFunction mapper)
Returns a LongStream
consisting of the results of applying the given function to the elements of this stream.
This is an intermediate operation.
 Parameters:

mapper
 a noninterfering, stateless function to apply to each element  Returns:
 the new stream
flatMap
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. 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
 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 to Double.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 to Double.compare(double, double)
.
This is a stateful intermediate operation.
 Returns:
 the result stream
peek
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.
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
DoubleStream limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize
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
DoubleStream 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.
 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
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. 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
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. 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
void forEach(DoubleConsumer 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.
 Parameters:

action
 a noninterfering action to perform on the elements
forEachOrdered
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.
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
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. This is equivalent to:
double result = identity; for (double element : this stream) result = accumulator.applyAsDouble(result, element) return result;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.
 API Note:
 Sum, min, max, and average are all special cases of reduction. Summing a stream of numbers can be expressed as:
double sum = numbers.reduce(0, (a, b) > a+b);
or more compactly: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 function 
op
 an associative, noninterfering, stateless function for combining two values  Returns:
 the result of the reduction
 See Also:

sum()
,min()
,max()
,average()
reduce
OptionalDouble reduce(DoubleBinaryOperator op)
Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalDouble
describing the reduced value, if any. This is equivalent to:
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();but is not constrained to execute sequentially.
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
<R> R collect(Supplier<R> supplier, ObjDoubleConsumer<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 (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:
return reduce(0, Double::sum);However, since floatingpoint summation is not exact, the above code is not necessarily equivalent to the summation computation done by this method.
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 an OptionalDouble
describing the minimum element of this stream, or an empty OptionalDouble if this stream is empty. The minimum element will be Double.NaN
if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to:
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 an OptionalDouble
describing the maximum element of this stream, or an empty OptionalDouble if this stream is empty. The maximum element will be Double.NaN
if any stream element was NaN. Unlike the numerical comparison operators, this method considers negative zero to be strictly smaller than positive zero. This is a special case of a reduction and is equivalent to:
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:
DoubleStream s = DoubleStream.of(1, 2, 3, 4); long count = s.peek(System.out::println).count();
The number of elements covered by the stream source is known and the intermediate operation,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 an OptionalDouble
describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty.
The computed average can vary numerically and have the special case behavior as computing the sum; see sum()
for details.
The average is a special case of a reduction.
This is a terminal operation.
 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 a DoubleSummaryStatistics
describing various summary data about the elements of this stream. This is a special case of a reduction.
This is a terminal operation.
 Returns:
 a
DoubleSummaryStatistics
describing various summary data about the elements of this stream
anyMatch
boolean anyMatch(DoublePredicate 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 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
boolean allMatch(DoublePredicate 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 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
boolean noneMatch(DoublePredicate 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 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 an OptionalDouble
describing the first element of this stream, or an empty OptionalDouble
if the stream is empty. If the stream has no encounter order, then any element may be returned.
This is a 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 an OptionalDouble
describing some element of the stream, or an empty OptionalDouble
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
Stream<Double> boxed()
Returns a Stream
consisting of the elements of this stream, boxed to Double
.
This is an intermediate operation.
 Returns:
 a
Stream
consistent of the elements of this stream, each boxed to aDouble
builder
static DoubleStream.Builder builder()
Returns a builder for a DoubleStream
.
 Returns:
 a stream builder
empty
static DoubleStream empty()
Returns an empty sequential DoubleStream
.
 Returns:
 an empty sequential stream
of
static DoubleStream of(double t)
Returns a sequential DoubleStream
containing a single element.
 Parameters:

t
 the single element  Returns:
 a singleton sequential stream
of
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
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
.
The action of applying f
for one element happensbefore 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
 the initial element 
f
 a function to be applied to the previous element to produce a new element  Returns:
 a new sequential
DoubleStream
iterate
static DoubleStream iterate(double seed, DoublePredicate hasNext, DoubleUnaryOperator next)
Returns a sequential ordered DoubleStream
produced by iterative application of the given next
function to an initial element, conditioned on satisfying the given hasNext
predicate. The stream terminates as soon as the hasNext
predicate returns false.
DoubleStream.iterate
should produce the same sequence of elements as produced by the corresponding 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 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 happensbefore the action of applying the next
function to that element. The action of applying the next
function for one element happensbefore 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
 the initial element 
hasNext
 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
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
 theDoubleSupplier
for generated elements  Returns:
 a new infinite sequential unordered
DoubleStream
concat
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.
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 stream 
b
 the second stream  Returns:
 the concatenation of the two input streams