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.Stream
,
java.util.streamModifier and Type  Interface and Description 

static interface 
DoubleStream.Builder
A mutable builder for a
DoubleStream . 
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 arithmetic
mean 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 . 
static DoubleStream.Builder 
builder()
Returns a builder for a
DoubleStream . 
<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.

static DoubleStream 
empty()
Returns an empty sequential
DoubleStream . 
DoubleStream 
filter(DoublePredicate predicate)
Returns 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, or an empty OptionalDouble 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 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. 
PrimitiveIterator.OfDouble 
iterator()
Returns an iterator for the elements of this stream.

DoubleStream 
limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than
maxSize 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 an
IntStream consisting of the results of applying the
given function to the elements of this stream. 
LongStream 
mapToLong(DoubleToLongFunction mapper)
Returns a
LongStream 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 objectvalued
Stream consisting of the results of
applying the given function to the elements of this stream. 
OptionalDouble 
max()
Returns an
OptionalDouble describing the maximum element of this
stream, or an empty OptionalDouble if this stream is empty. 
OptionalDouble 
min()
Returns an
OptionalDouble 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... 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. 
DoubleStream 
parallel()
Returns an equivalent stream that is parallel.

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.

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. 
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.

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

DoubleStream 
skip(long n)
Returns a stream consisting of the remaining elements of this stream
after discarding the first
n elements of the stream. 
DoubleStream 
sorted()
Returns a stream consisting of the elements of this stream in sorted
order.

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

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()
Returns an array containing the elements of this stream.

close, isParallel, onClose, unordered
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 apply to each element<U> Stream<U> mapToObj(DoubleFunction<? extends U> mapper)
Stream
consisting of the results of
applying the given function to the elements of this stream.
This is an intermediate operation.
U
 the element type of the new streammapper
 a noninterfering,
stateless
function to apply 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 apply 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 apply to each elementDoubleStream flatMap(DoubleFunction<? extends DoubleStream> mapper)
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.
mapper
 a noninterfering,
stateless
function to apply to each element which produces a
DoubleStream
of new valuesStream.flatMap(Function)
DoubleStream distinct()
Double.compare(double, double)
.
This is a stateful intermediate operation.
DoubleStream sorted()
Double.compare(double, double)
.
This is a stateful intermediate operation.
DoubleStream peek(DoubleConsumer action)
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.
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();
action
 a
noninterfering action to perform on the elements as
they are consumed from the streamDoubleStream limit(long maxSize)
maxSize
in length.
limit()
is generally a cheap operation on sequential
stream pipelines, it can be quite expensive on ordered parallel pipelines,
especially for large values of maxSize
, since limit(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 as generate(DoubleSupplier)
) or removing the
ordering constraint with BaseStream.unordered()
may result in significant
speedups of limit()
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 with
limit()
in parallel pipelines, switching to sequential execution
with sequential()
may improve performance.maxSize
 the number of elements the stream should be limited toIllegalArgumentException
 if maxSize
is negativeDoubleStream skip(long n)
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.
skip()
is generally a cheap operation on sequential
stream pipelines, it can be quite expensive on ordered parallel pipelines,
especially for large values of n
, since skip(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 as generate(DoubleSupplier)
) or removing the
ordering constraint with BaseStream.unordered()
may result in significant
speedups of skip()
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 with
skip()
in parallel pipelines, switching to sequential execution
with sequential()
may improve performance.n
 the number of leading elements to skipIllegalArgumentException
 if n
is negativevoid forEach(DoubleConsumer action)
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.
action
 a
noninterfering action to perform on the elementsvoid forEachOrdered(DoubleConsumer action)
This is a terminal operation.
action
 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.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.
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.
identity
 the identity value for the accumulating functionop
 an associative,
noninterfering,
stateless
function for combining two valuessum()
,
min()
,
max()
,
average()
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.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.
op
 an associative,
noninterfering,
stateless
function for combining two valuesreduce(double, DoubleBinaryOperator)
<R> R collect(Supplier<R> supplier, 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 = 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.
R
 type of the resultsupplier
 a 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);
However, since floatingpoint summation is not exact, the above
code is not necessarily equivalent to the summation computation
done by this method.
If any stream element is a NaN or the sum is at any point a NaN
then the sum will be NaN.
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.
This is a terminal operation.
OptionalDouble min()
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.
OptionalDouble
containing the minimum element of this
stream, or an empty optional if the stream is emptyOptionalDouble max()
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.
OptionalDouble
containing the maximum element of this
stream, or an empty optional if the stream is emptylong count()
return mapToLong(e > 1L).sum();
This is a terminal operation.
OptionalDouble average()
OptionalDouble
describing the arithmetic
mean of elements of this stream, or an empty optional if this
stream is empty.
If any recorded value is a NaN or the sum is at any point a NaN
then the average will be NaN.
The average returned can vary depending upon the order in
which values are recorded.
This method may be implemented using compensated summation or
other technique to reduce the error bound in the numerical sum
used to compute the average.
The average is a special case of a reduction.
This is a terminal operation.
OptionalDouble
containing the average element of this
stream, or an empty optional if the stream is emptyDoubleSummaryStatistics summaryStatistics()
DoubleSummaryStatistics
describing various summary data
about the elements of this stream. This is a special
case of a reduction.
This is a terminal operation.
DoubleSummaryStatistics
describing various summary data
about the elements of this streamboolean anyMatch(DoublePredicate predicate)
false
is returned and the predicate is not evaluated.
This is a shortcircuiting terminal operation.
predicate
 a noninterfering,
stateless
predicate to apply to elements of this streamtrue
if any elements of the stream match the provided
predicate, otherwise false
boolean allMatch(DoublePredicate predicate)
true
is
returned and the predicate is not evaluated.
This is a shortcircuiting terminal operation.
true
(regardless of P(x)).predicate
 a noninterfering,
stateless
predicate to apply to elements of this streamtrue
if either all elements of the stream match the
provided predicate or the stream is empty, otherwise false
boolean noneMatch(DoublePredicate predicate)
true
is
returned and the predicate is not evaluated.
This is a shortcircuiting terminal operation.
true
, regardless of P(x).predicate
 a noninterfering,
stateless
predicate to apply to elements of this streamtrue
if either no elements of the stream match the
provided predicate or the stream is empty, otherwise false
OptionalDouble findFirst()
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.
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 a stable result
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
.
This is an intermediate operation.
Stream
consistent of the elements of this stream,
each boxed to a Double
DoubleStream sequential()
BaseStream
This is an intermediate operation.
sequential
in interface BaseStream<Double,DoubleStream>
DoubleStream parallel()
BaseStream
This is an intermediate operation.
parallel
in interface BaseStream<Double,DoubleStream>
PrimitiveIterator.OfDouble iterator()
BaseStream
This is a terminal operation.
iterator
in interface BaseStream<Double,DoubleStream>
Spliterator.OfDouble spliterator()
BaseStream
This is a terminal operation.
spliterator
in interface BaseStream<Double,DoubleStream>
static DoubleStream.Builder builder()
DoubleStream
.static DoubleStream empty()
DoubleStream
.static DoubleStream of(double t)
DoubleStream
containing a single element.t
 the single elementstatic DoubleStream of(double... values)
values
 the elements of the new streamstatic DoubleStream iterate(double seed, DoubleUnaryOperator f)
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
.
seed
 the initial elementf
 a function to be applied to to the previous element to produce
a new elementDoubleStream
static DoubleStream generate(DoubleSupplier s)
DoubleSupplier
. This is suitable for
generating constant streams, streams of random elements, etc.s
 the DoubleSupplier
for generated elementsDoubleStream
static DoubleStream concat(DoubleStream a, DoubleStream b)
StackOverflowException
.a
 the first streamb
 the second stream