LongStream
public
interface
LongStream
implements
BaseStream<Long, LongStream>
java.util.stream.LongStream 
A sequence of primitive longvalued elements supporting sequential and parallel
aggregate operations. This is the long
primitive specialization of
Stream
.
The following example illustrates an aggregate operation using
Stream
and LongStream
, computing the sum of the weights of the
red widgets:
long sum = widgets.stream()
.filter(w > w.getColor() == RED)
.mapToLong(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.
See also:
Summary
Nested classes  

interface 
LongStream.Builder
A mutable builder for a 
Public methods  

abstract
boolean

allMatch(LongPredicate predicate)
Returns whether all elements of this stream match the provided predicate. 
abstract
boolean

anyMatch(LongPredicate predicate)
Returns whether any elements of this stream match the provided predicate. 
abstract
DoubleStream

asDoubleStream()
Returns a 
abstract
OptionalDouble

average()
Returns an 
abstract
Stream<Long>

boxed()
Returns a 
static
LongStream.Builder

builder()
Returns a builder for a 
abstract
<R>
R

collect(Supplier<R> supplier, ObjLongConsumer<R> accumulator, BiConsumer<R, R> combiner)
Performs a mutable reduction operation on the elements of this stream. 
static
LongStream

concat(LongStream a, LongStream 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. 
abstract
long

count()
Returns the count of elements in this stream. 
abstract
LongStream

distinct()
Returns a stream consisting of the distinct elements of this stream. 
static
LongStream

empty()
Returns an empty sequential 
abstract
LongStream

filter(LongPredicate predicate)
Returns a stream consisting of the elements of this stream that match the given predicate. 
abstract
OptionalLong

findAny()
Returns an 
abstract
OptionalLong

findFirst()
Returns an 
abstract
LongStream

flatMap(LongFunction<? extends LongStream> 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. 
abstract
void

forEach(LongConsumer action)
Performs an action for each element of this stream. 
abstract
void

forEachOrdered(LongConsumer 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
LongStream

generate(LongSupplier s)
Returns an infinite sequential unordered stream where each element is
generated by the provided 
static
LongStream

iterate(long seed, LongUnaryOperator f)
Returns an infinite sequential ordered 
abstract
PrimitiveIterator.OfLong

iterator()
Returns an iterator for the elements of this stream. 
abstract
LongStream

limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than 
abstract
LongStream

map(LongUnaryOperator mapper)
Returns a stream consisting of the results of applying the given function to the elements of this stream. 
abstract
DoubleStream

mapToDouble(LongToDoubleFunction mapper)
Returns a 
abstract
IntStream

mapToInt(LongToIntFunction mapper)
Returns an 
abstract
<U>
Stream<U>

mapToObj(LongFunction<? extends U> mapper)
Returns an objectvalued 
abstract
OptionalLong

max()
Returns an 
abstract
OptionalLong

min()
Returns an 
abstract
boolean

noneMatch(LongPredicate predicate)
Returns whether no elements of this stream match the provided predicate. 
static
LongStream

of(long... values)
Returns a sequential ordered stream whose elements are the specified values. 
static
LongStream

of(long t)
Returns a sequential 
abstract
LongStream

parallel()
Returns an equivalent stream that is parallel. 
abstract
LongStream

peek(LongConsumer 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. 
static
LongStream

range(long startInclusive, long endExclusive)
Returns a sequential ordered 
static
LongStream

rangeClosed(long startInclusive, long endInclusive)
Returns a sequential ordered 
abstract
OptionalLong

reduce(LongBinaryOperator op)
Performs a reduction on the
elements of this stream, using an
associative accumulation
function, and returns an 
abstract
long

reduce(long identity, LongBinaryOperator 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. 
abstract
LongStream

sequential()
Returns an equivalent stream that is sequential. 
abstract
LongStream

skip(long n)
Returns a stream consisting of the remaining elements of this stream
after discarding the first 
abstract
LongStream

sorted()
Returns a stream consisting of the elements of this stream in sorted order. 
abstract
Spliterator.OfLong

spliterator()
Returns a spliterator for the elements of this stream. 
abstract
long

sum()
Returns the sum of elements in this stream. 
abstract
LongSummaryStatistics

summaryStatistics()
Returns a 
abstract
long[]

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

Public methods
allMatch
boolean allMatch (LongPredicate 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 
LongPredicate : a noninterfering,
stateless
predicate to apply to elements of this stream 
Returns  

boolean 
true if either all elements of the stream match the
provided predicate or the stream is empty, otherwise false

anyMatch
boolean anyMatch (LongPredicate 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 
LongPredicate : a noninterfering,
stateless
predicate to apply to elements of this stream 
Returns  

boolean 
true if any elements of the stream match the provided
predicate, otherwise false

asDoubleStream
DoubleStream asDoubleStream ()
Returns a DoubleStream
consisting of the elements of this stream,
converted to double
.
This is an intermediate operation.
Returns  

DoubleStream 
a DoubleStream consisting of the elements of this stream,
converted to double

average
OptionalDouble average ()
Returns an OptionalDouble
describing the arithmetic mean of elements of
this stream, or an empty optional if this stream is empty. This is a
special case of a
reduction.
This is a terminal operation.
Returns  

OptionalDouble 
an OptionalDouble containing the average element of this
stream, or an empty optional if the stream is empty

boxed
Stream<Long> boxed ()
Returns a Stream
consisting of the elements of this stream,
each boxed to a Long
.
This is an intermediate operation.
Returns  

Stream<Long> 
a Stream consistent of the elements of this stream,
each boxed to Long

builder
LongStream.Builder builder ()
Returns a builder for a LongStream
.
Returns  

LongStream.Builder 
a stream builder 
collect
R collect (Supplier<R> supplier, ObjLongConsumer<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 (long element : this stream)
accumulator.accept(result, element);
return result;
Like reduce(long, LongBinaryOperator)
, collect
operations
can be parallelized without requiring additional synchronization.
This is a terminal operation.
Parameters  

supplier 
Supplier : 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 
ObjLongConsumer : an associative,
noninterfering,
stateless
function for incorporating an additional element into a result 
combiner 
BiConsumer : an associative,
noninterfering,
stateless
function for combining two values, which must be
compatible with the accumulator function 
Returns  

R 
the result of the reduction 
concat
LongStream concat (LongStream a, LongStream b)
Creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream. The resulting stream is ordered if both of the input streams are ordered, and parallel if either of the input streams is parallel. When the resulting stream is closed, the close handlers for both input streams are invoked.
Implementation Note:
 Use caution when constructing streams from repeated concatenation.
Accessing an element of a deeply concatenated stream can result in deep
call chains, or even
StackOverflowException
.
Parameters  

a 
LongStream : the first stream 
b 
LongStream : the second stream 
Returns  

LongStream 
the concatenation of the two input streams 
count
long count ()
Returns the count of elements in this stream. This is a special case of a reduction and is equivalent to:
return map(e > 1L).sum();
This is a terminal operation.
Returns  

long 
the count of elements in this stream 
distinct
LongStream distinct ()
Returns a stream consisting of the distinct elements of this stream.
This is a stateful intermediate operation.
Returns  

LongStream 
the new stream 
empty
LongStream empty ()
Returns an empty sequential LongStream
.
Returns  

LongStream 
an empty sequential stream 
filter
LongStream filter (LongPredicate predicate)
Returns a stream consisting of the elements of this stream that match the given predicate.
This is an intermediate operation.
Parameters  

predicate 
LongPredicate : a noninterfering,
stateless
predicate to apply to each element to determine if it
should be included 
Returns  

LongStream 
the new stream 
findAny
OptionalLong findAny ()
Returns an OptionalLong
describing some element of the stream, or
an empty OptionalLong
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  

OptionalLong 
an OptionalLong describing some element of this stream,
or an empty OptionalLong if the stream is empty 
See also:
findFirst
OptionalLong findFirst ()
Returns an OptionalLong
describing the first element of this
stream, or an empty OptionalLong
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  

OptionalLong 
an OptionalLong describing the first element of this
stream, or an empty OptionalLong if the stream is empty

flatMap
LongStream flatMap (LongFunction<? extends LongStream> 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 
LongFunction : a noninterfering,
stateless
function to apply to each element which produces a
LongStream of new values 
Returns  

LongStream 
the new stream 
See also:
forEach
void forEach (LongConsumer 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 
LongConsumer : a
noninterfering action to perform on the elements

forEachOrdered
void forEachOrdered (LongConsumer 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 
LongConsumer : a
noninterfering action to perform on the elements 
See also:
generate
LongStream generate (LongSupplier s)
Returns an infinite sequential unordered stream where each element is
generated by the provided LongSupplier
. This is suitable for
generating constant streams, streams of random elements, etc.
Parameters  

s 
LongSupplier : the LongSupplier for generated elements 
Returns  

LongStream 
a new infinite sequential unordered LongStream

iterate
LongStream iterate (long seed, LongUnaryOperator f)
Returns an infinite sequential ordered LongStream
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 LongStream
will
be the provided seed
. For n > 0
, the element at position
n
, will be the result of applying the function f
to the
element at position n  1
.
Parameters  

seed 
long : the initial element 
f 
LongUnaryOperator : a function to be applied to to the previous element to produce
a new element 
Returns  

LongStream 
a new sequential LongStream

iterator
PrimitiveIterator.OfLong iterator ()
Returns an iterator for the elements of this stream.
This is a terminal operation.
Returns  

PrimitiveIterator.OfLong 
the element iterator for this stream 
limit
LongStream limit (long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than maxSize
in length.
This is a shortcircuiting stateful intermediate operation.
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(LongSupplier)
) or removing the ordering constraint withunordered()
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 withsequential()
may improve performance.
Parameters  

maxSize 
long : the number of elements the stream should be limited to 
Returns  

LongStream 
the new stream 
Throws  

IllegalArgumentException 
if maxSize is negative

map
LongStream map (LongUnaryOperator 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 
LongUnaryOperator : a noninterfering,
stateless
function to apply to each element 
Returns  

LongStream 
the new stream 
mapToDouble
DoubleStream mapToDouble (LongToDoubleFunction mapper)
Returns a DoubleStream
consisting of the results of applying the
given function to the elements of this stream.
This is an intermediate operation.
Parameters  

mapper 
LongToDoubleFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

DoubleStream 
the new stream 
mapToInt
IntStream mapToInt (LongToIntFunction 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 
LongToIntFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

IntStream 
the new stream 
mapToObj
Stream<U> mapToObj (LongFunction<? 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.
Parameters  

mapper 
LongFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

Stream<U> 
the new stream 
max
OptionalLong max ()
Returns an OptionalLong
describing the maximum 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(Long::max);
This is a terminal operation.
Returns  

OptionalLong 
an OptionalLong containing the maximum element of this
stream, or an empty OptionalLong if the stream is empty

min
OptionalLong min ()
Returns an OptionalLong
describing the minimum 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(Long::min);
This is a terminal operation.
Returns  

OptionalLong 
an OptionalLong containing the minimum element of this
stream, or an empty OptionalLong if the stream is empty

noneMatch
boolean noneMatch (LongPredicate 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 
LongPredicate : a noninterfering,
stateless
predicate to apply to elements of this stream 
Returns  

boolean 
true if either no elements of the stream match the
provided predicate or the stream is empty, otherwise false

of
LongStream of (long... values)
Returns a sequential ordered stream whose elements are the specified values.
Parameters  

values 
long : the elements of the new stream 
Returns  

LongStream 
the new stream 
of
LongStream of (long t)
Returns a sequential LongStream
containing a single element.
Parameters  

t 
long : the single element 
Returns  

LongStream 
a singleton sequential stream 
parallel
LongStream parallel ()
Returns an equivalent stream that is parallel. May return itself, either because the stream was already parallel, or because the underlying stream state was modified to be parallel.
This is an intermediate operation.
Returns  

LongStream 
a parallel stream 
peek
LongStream peek (LongConsumer 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:
LongStream.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();
Parameters  

action 
LongConsumer : a
noninterfering action to perform on the elements as
they are consumed from the stream 
Returns  

LongStream 
the new stream 
range
LongStream range (long startInclusive, long endExclusive)
Returns a sequential ordered LongStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by an incremental step of
1
.
API Note:
An equivalent sequence of increasing values can be produced sequentially using a
for
loop as follows:for (long i = startInclusive; i < endExclusive ; i++) { ... }
Parameters  

startInclusive 
long : the (inclusive) initial value 
endExclusive 
long : the exclusive upper bound 
Returns  

LongStream 
a sequential LongStream for the range of long
elements

rangeClosed
LongStream rangeClosed (long startInclusive, long endInclusive)
Returns a sequential ordered LongStream
from startInclusive
(inclusive) to endInclusive
(inclusive) by an incremental step of
1
.
API Note:
An equivalent sequence of increasing values can be produced sequentially using a
for
loop as follows:for (long i = startInclusive; i <= endInclusive ; i++) { ... }
Parameters  

startInclusive 
long : the (inclusive) initial value 
endInclusive 
long : the inclusive upper bound 
Returns  

LongStream 
a sequential LongStream for the range of long
elements

reduce
OptionalLong reduce (LongBinaryOperator op)
Performs a reduction on the
elements of this stream, using an
associative accumulation
function, and returns an OptionalLong
describing the reduced value,
if any. This is equivalent to:
boolean foundAny = false;
long result = null;
for (long element : this stream) {
if (!foundAny) {
foundAny = true;
result = element;
}
else
result = accumulator.applyAsLong(result, element);
}
return foundAny ? OptionalLong.of(result) : OptionalLong.empty();
but is not constrained to execute sequentially.
The accumulator
function must be an
associative function.
This is a terminal operation.
Parameters  

op 
LongBinaryOperator : an associative,
noninterfering,
stateless
function for combining two values 
Returns  

OptionalLong 
the result of the reduction 
See also:
reduce
long reduce (long identity, LongBinaryOperator 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:
long result = identity;
for (long element : this stream)
result = accumulator.applyAsLong(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:
or more compactly:long sum = integers.reduce(0, (a, b) > a+b);
long sum = integers.reduce(0, Long::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 
long : the identity value for the accumulating function 
op 
LongBinaryOperator : an associative,
noninterfering,
stateless
function for combining two values 
Returns  

long 
the result of the reduction 
sequential
LongStream sequential ()
Returns an equivalent stream that is sequential. May return itself, either because the stream was already sequential, or because the underlying stream state was modified to be sequential.
This is an intermediate operation.
Returns  

LongStream 
a sequential stream 
skip
LongStream 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(LongSupplier)
) or removing the ordering constraint withunordered()
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 withsequential()
may improve performance.
Parameters  

n 
long : the number of leading elements to skip 
Returns  

LongStream 
the new stream 
Throws  

IllegalArgumentException 
if n is negative

sorted
LongStream sorted ()
Returns a stream consisting of the elements of this stream in sorted order.
This is a stateful intermediate operation.
Returns  

LongStream 
the new stream 
spliterator
Spliterator.OfLong spliterator ()
Returns a spliterator for the elements of this stream.
This is a terminal operation.
Returns  

Spliterator.OfLong 
the element spliterator for this stream 
sum
long sum ()
Returns the sum of elements in this stream. This is a special case of a reduction and is equivalent to:
return reduce(0, Long::sum);
This is a terminal operation.
Returns  

long 
the sum of elements in this stream 
summaryStatistics
LongSummaryStatistics summaryStatistics ()
Returns a LongSummaryStatistics
describing various summary data
about the elements of this stream. This is a special case of a
reduction.
This is a terminal operation.
Returns  

LongSummaryStatistics 
a LongSummaryStatistics describing various summary data
about the elements of this stream

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

long[] 
an array containing the elements of this stream 