public interface DoubleStream
filter
and map
, and
consuming operations, such as forEach
, findFirst
, and iterator
. Once an operation has been performed on a stream, it
is considered consumed and no longer usable for other operations.
For sequential stream pipelines, all operations are performed in the encounter order of the pipeline source, if the pipeline source has a defined encounter order.
For parallel stream pipelines, unless otherwise specified, intermediate stream operations preserve the encounter order of their source, and terminal operations respect the encounter order of their source, if the source has an encounter order.
iterator()
or spliterator()
operations to
perform a controlled traversal.
Unless otherwise noted, passing a null
argument to any stream
method may result in a NullPointerException
.
Modifier and Type  Method and 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
OptionalDouble describing the average of elements of this
stream, or an empty optional if this stream is empty. 
Stream<Double> 
boxed()
Returns a
Stream consisting of the elements of this stream,
boxed to Double . 
<R> R 
collect(Supplier<R> resultFactory,
ObjDoubleConsumer<R> accumulator,
BiConsumer<R,R> combiner)
Performs a mutable
reduction operation on the elements of this stream.

long 
count()
Returns the count of elements in this stream.

DoubleStream 
distinct()
Produces a stream consisting of the distinct elements of this stream.

DoubleStream 
filter(DoublePredicate predicate)
Produces a stream consisting of the elements of this stream that match
the given predicate.

OptionalDouble 
findAny()
Returns an
OptionalDouble describing some element of the stream, or an
empty OptionalDouble if the stream is empty. 
OptionalDouble 
findFirst()
Returns an
OptionalDouble describing the first element of this stream
(in the encounter order), or an empty OptionalDouble if the stream is
empty. 
DoubleStream 
flatMap(DoubleFunction<? extends DoubleStream> mapper)
Produces a stream consisting of the results of replacing each
element of this stream with the contents of the stream
produced by applying the provided function to each element.

DoubleStream 
flatMap(FlatMapper.OfDoubleToDouble mapper)
Produces a stream consisting of the results of replacing each
element of this stream with zero or more transformed values, according
to the transformation encoded in the provided
FlatMapper.OfDoubleToDouble . 
void 
forEach(DoubleConsumer consumer)
Performs an operation for each element of this stream.

void 
forEachOrdered(DoubleConsumer consumer)
Performs an operation for each element of this stream, guaranteeing that
each element is processed in encounter order for streams that have a
defined encounter order.

boolean 
isParallel()
Returns whether this stream, when executed, will execute in parallel.

PrimitiveIterator.OfDouble 
iterator()
Returns an iterator for the elements of this stream.

DoubleStream 
limit(long maxSize)
Produces a stream consisting of the elements of this stream,
truncated to be no longer than
maxSize in length. 
DoubleStream 
map(DoubleUnaryOperator mapper)
Produces a stream consisting of the results of applying the given
function to the elements of this stream.

IntStream 
mapToInt(DoubleToIntFunction mapper)
Produces an
IntStream consisting of the results of applying
the given function to the elements of this stream. 
LongStream 
mapToLong(DoubleToLongFunction mapper)
Produces a
LongStream consisting of the results of applying
the given function to the elements of this stream. 
<U> Stream<U> 
mapToObj(DoubleFunction<U> mapper)
Produces an objectvalued
Stream consisting of the results of
applying the given function to the elements of this stream. 
OptionalDouble 
max()
Returns an
OptionalDouble describing the maximal element of this
stream, or an empty optional if this stream is empty. 
OptionalDouble 
min()
Returns an
OptionalDouble describing the minimal element of this
stream, or an empty optional if this stream is empty. 
boolean 
noneMatch(DoublePredicate predicate)
Returns whether no elements of this stream match the provided
predicate.

DoubleStream 
parallel()
Produces an equivalent stream that is parallel.

DoubleStream 
peek(DoubleConsumer consumer)
Produces 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.

OptionalDouble 
reduce(DoubleBinaryOperator op)
Performs a reduction on the
elements of this stream, using an
associative accumulation
function, and return an
OptionalDouble describing the reduced value,
if any. 
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 return the reduced value.

DoubleStream 
sequential()
Produces an equivalent stream that is sequential.

DoubleStream 
sorted()
Produces a stream consisting of the elements of this stream in sorted
order.

Spliterator.OfDouble 
spliterator()
Returns a spliterator for the elements of this stream.

DoubleStream 
substream(long startingOffset)
Produces a stream consisting of the elements of this stream,
discarding the first
startingOffset elements. 
DoubleStream 
substream(long startingOffset,
long endingOffset)
Produces a stream consisting of the elements of this stream,
discarding the first
startingOffset elements, and truncating the
remainder to be no longer than maxSize in length. 
double 
sum()
Returns the sum of elements in this stream.

DoubleSummaryStatistics 
summaryStatistics()
Returns a
DoubleSummaryStatistics describing various
summary data about the elements of this stream. 
double[] 
toArray()
Produces an array containing the elements of this stream.

DoubleStream filter(DoublePredicate predicate)
This is an intermediate operation.
predicate
 A
noninterfering, stateless predicate to apply to
each element to determine if it should be includedDoubleStream map(DoubleUnaryOperator mapper)
This is an intermediate operation.
mapper
 a
noninterfering, stateless function to be applied to
each element<U> Stream<U> mapToObj(DoubleFunction<U> mapper)
Stream
consisting of the results of
applying the given function to the elements of this stream.
This is an intermediate operation.
mapper
 A
noninterfering, stateless function to be applied to
each elementIntStream mapToInt(DoubleToIntFunction mapper)
IntStream
consisting of the results of applying
the given function to the elements of this stream.
This is an intermediate operation.
mapper
 A
noninterfering, stateless function to be applied to
each elementLongStream mapToLong(DoubleToLongFunction mapper)
LongStream
consisting of the results of applying
the given function to the elements of this stream.
This is an intermediate operation.
mapper
 A
noninterfering, stateless function to be applied to
each elementDoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper)
This is an intermediate operation.
mapper
 A
noninterfering, stateless function to be applied to
each element which produces a stream of new
valuesStream.flatMap(Function)
This implementation is likely to be less efficient than the other
form of flatMap(FlatMapper.OfDoubleToDouble)
, and is provided for
convenience.
DoubleStream flatMap(FlatMapper.OfDoubleToDouble mapper)
FlatMapper.OfDoubleToDouble
.
This is an intermediate operation.
mapper
 A
noninterfering, stateless FlatMapper.OfDoubleToDouble
that transforms each element into zero or more resulting
valuesflatMap
is usually less convenient to use than the
flatMap(DoubleFunction)
form, but is often considerably more
efficient because it eliminates the overhead of stream construction
and traversal.DoubleStream distinct()
This is a stateful intermediate operation.
DoubleStream sorted()
This is a stateful intermediate operation.
DoubleStream peek(DoubleConsumer consumer)
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.
consumer
 A
noninterfering action to perform on the elements as
they are consumed from the streamlist.stream() .filter(filteringFunction) .peek(e > {System.out.println("Filtered value: " + e); }); .map(mappingFunction) .peek(e > {System.out.println("Mapped value: " + e); }); .collect(Collectors.toDoubleSummaryStastistics());
DoubleStream limit(long maxSize)
maxSize
in length.
maxSize
 the number of elements the stream should be limited toDoubleStream substream(long startingOffset)
startingOffset
elements.
This is a stateful intermediate operation.
startingOffset
 the number of leading elements to be skippedDoubleStream substream(long startingOffset, long endingOffset)
startingOffset
elements, and truncating the
remainder to be no longer than maxSize
in length.
startingOffset
 the starting position of the substream, inclusiveendingOffset
 the ending position of the substream, exclusivevoid forEach(DoubleConsumer consumer)
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 operation accesses shared state, it is responsible for providing the required synchronization.
consumer
 A
noninterfering action to perform on the elementsvoid forEachOrdered(DoubleConsumer consumer)
This is a terminal operation.
consumer
 A
noninterfering action to perform on the elementsforEach(DoubleConsumer)
double[] toArray()
This is a terminal operation.
double reduce(double identity, DoubleBinaryOperator op)
double result = identity; for (double element : this stream) result = accumulator.apply(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.
identity
 The identity value for the accumulating functionop
 An associative
noninterfering,
stateless function for combining two valuessum()
,
min()
,
max()
,
average()
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.
OptionalDouble reduce(DoubleBinaryOperator op)
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.apply(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.
op
 An associative
noninterfering,
stateless function for combining two valuesreduce(double, DoubleBinaryOperator)
<R> R collect(Supplier<R> resultFactory, ObjDoubleConsumer<R> accumulator, BiConsumer<R,R> combiner)
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 = resultFactory.get(); for (double element : this stream) accumulator.accept(result, element); return result;Like
reduce(double, DoubleBinaryOperator)
, collect
operations
can be parallelized without requiring additional sychronization.
This is a terminal operation.
R
 Type of the resultresultFactory
 Function that creates a new 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 for incorporating an additional
element into a resultcombiner
 An associative
noninterfering,
stateless function for combining two values, which
must be compatible with the accumulator functionStream.collect(Supplier, BiConsumer, BiConsumer)
double sum()
return reduce(0, Double::sum);
OptionalDouble min()
OptionalDouble
describing the minimal 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(Double::min);
OptionalDouble
OptionalDouble max()
OptionalDouble
describing the maximal 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(Double::max);
OptionalDouble
long count()
return mapToLong(e > 1L).sum();
OptionalDouble average()
OptionalDouble
describing the average of elements of this
stream, or an empty optional if this stream is empty. This is a special
case of a reduction.OptionalDouble
DoubleSummaryStatistics summaryStatistics()
DoubleSummaryStatistics
describing various
summary data about the elements of this stream. This is a special
case of a reduction.DoubleSummaryStatistics
describing various
summary data about the elements of this streamboolean anyMatch(DoublePredicate predicate)
This is a shortcircuiting terminal operation.
predicate
 A noninterfering,
stateless predicate to apply to elements of this
streamboolean allMatch(DoublePredicate predicate)
This is a shortcircuiting terminal operation.
predicate
 A noninterfering,
stateless predicate to apply to elements of this streamboolean noneMatch(DoublePredicate predicate)
This is a shortcircuiting terminal operation.
predicate
 A noninterfering,
stateless predicate to apply to elements of this streamOptionalDouble findFirst()
OptionalDouble
describing the first element of this stream
(in the encounter order), or an empty OptionalDouble
if the stream is
empty.
This is a shortcircuiting terminal operation.
OptionalDouble
describing the first element of this stream,
or an empty OptionalDouble
if the stream is emptyOptionalDouble findAny()
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 the first element
in the encounter order is desired, use findFirst()
instead.)
OptionalDouble
describing some element of this stream, or an
empty OptionalDouble
if the stream is emptyfindFirst()
Stream<Double> boxed()
Stream
consisting of the elements of this stream,
boxed to Double
.Stream
consistent of the elements of this stream,
boxed to Double
DoubleStream sequential()
This is a stateful intermediate operation.
DoubleStream parallel()
This is a stateful intermediate operation.
PrimitiveIterator.OfDouble iterator()
This is a terminal operation.
Spliterator.OfDouble spliterator()
This is a terminal operation.
boolean isParallel()
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