IntStream
public
interface
IntStream
implements
BaseStream<Integer, IntStream>
java.util.stream.IntStream 
A sequence of primitive intvalued elements supporting sequential and parallel
aggregate operations. This is the int
primitive specialization of
Stream
.
The following example illustrates an aggregate operation using
Stream
and IntStream
, computing the sum of the weights of the
red widgets:
int sum = widgets.stream()
.filter(w > w.getColor() == RED)
.mapToInt(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 
IntStream.Builder
A mutable builder for an 
Public methods  

abstract
boolean

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

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

asDoubleStream()
Returns a 
abstract
LongStream

asLongStream()
Returns a 
abstract
OptionalDouble

average()
Returns an 
abstract
Stream<Integer>

boxed()
Returns a 
static
IntStream.Builder

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

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

concat(IntStream a, IntStream 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
IntStream

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

empty()
Returns an empty sequential 
abstract
IntStream

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

findAny()
Returns an 
abstract
OptionalInt

findFirst()
Returns an 
abstract
IntStream

flatMap(IntFunction<? extends IntStream> 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(IntConsumer action)
Performs an action for each element of this stream. 
abstract
void

forEachOrdered(IntConsumer 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
IntStream

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

iterate(int seed, IntUnaryOperator f)
Returns an infinite sequential ordered 
abstract
PrimitiveIterator.OfInt

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

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

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

mapToDouble(IntToDoubleFunction mapper)
Returns a 
abstract
LongStream

mapToLong(IntToLongFunction mapper)
Returns a 
abstract
<U>
Stream<U>

mapToObj(IntFunction<? extends U> mapper)
Returns an objectvalued 
abstract
OptionalInt

max()
Returns an 
abstract
OptionalInt

min()
Returns an 
abstract
boolean

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

of(int t)
Returns a sequential 
static
IntStream

of(int... values)
Returns a sequential ordered stream whose elements are the specified values. 
abstract
IntStream

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

peek(IntConsumer 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
IntStream

range(int startInclusive, int endExclusive)
Returns a sequential ordered 
static
IntStream

rangeClosed(int startInclusive, int endInclusive)
Returns a sequential ordered 
abstract
OptionalInt

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

reduce(int identity, IntBinaryOperator 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
IntStream

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

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

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

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

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

summaryStatistics()
Returns an 
abstract
int[]

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

Public methods
allMatch
public abstract boolean allMatch (IntPredicate 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 
IntPredicate : 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
public abstract boolean anyMatch (IntPredicate 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 
IntPredicate : 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
public abstract 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

asLongStream
public abstract LongStream asLongStream ()
Returns a LongStream
consisting of the elements of this stream,
converted to long
.
This is an intermediate operation.
Returns  

LongStream 
a LongStream consisting of the elements of this stream,
converted to long

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

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

builder
public static IntStream.Builder builder ()
Returns a builder for an IntStream
.
Returns  

IntStream.Builder 
a stream builder 
collect
public abstract R collect (Supplier<R> supplier, ObjIntConsumer<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 (int element : this stream)
accumulator.accept(result, element);
return result;
Like reduce(int, IntBinaryOperator)
, 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 
ObjIntConsumer : 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
public static IntStream concat (IntStream a, IntStream 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 
IntStream : the first stream 
b 
IntStream : the second stream 
Returns  

IntStream 
the concatenation of the two input streams 
count
public abstract 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.
Returns  

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

IntStream 
the new stream 
empty
public static IntStream empty ()
Returns an empty sequential IntStream
.
Returns  

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

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

IntStream 
the new stream 
findAny
public abstract OptionalInt findAny ()
Returns an OptionalInt
describing some element of the stream, or
an empty OptionalInt
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  

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

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

flatMap
public abstract IntStream flatMap (IntFunction<? extends IntStream> 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 
IntFunction : a noninterfering,
stateless
function to apply to each element which produces an
IntStream of new values 
Returns  

IntStream 
the new stream 
See also:
forEach
public abstract void forEach (IntConsumer 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 
IntConsumer : a
noninterfering action to perform on the elements

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

s 
IntSupplier : the IntSupplier for generated elements 
Returns  

IntStream 
a new infinite sequential unordered IntStream

iterate
public static IntStream iterate (int seed, IntUnaryOperator f)
Returns an infinite sequential ordered IntStream
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 IntStream
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 
int : the initial element 
f 
IntUnaryOperator : a function to be applied to to the previous element to produce
a new element 
Returns  

IntStream 
A new sequential IntStream

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

PrimitiveIterator.OfInt 
the element iterator for this stream 
limit
public abstract IntStream 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(IntSupplier)
) 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 withsequential()
may improve performance.
Parameters  

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

IntStream 
the new stream 
Throws  

IllegalArgumentException 
if maxSize is negative

map
public abstract IntStream map (IntUnaryOperator 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 
IntUnaryOperator : a noninterfering,
stateless
function to apply to each element 
Returns  

IntStream 
the new stream 
mapToDouble
public abstract DoubleStream mapToDouble (IntToDoubleFunction 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 
IntToDoubleFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

DoubleStream 
the new stream 
mapToLong
public abstract LongStream mapToLong (IntToLongFunction 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 
IntToLongFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

LongStream 
the new stream 
mapToObj
public abstract Stream<U> mapToObj (IntFunction<? 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 
IntFunction : a noninterfering,
stateless
function to apply to each element 
Returns  

Stream<U> 
the new stream 
max
public abstract OptionalInt max ()
Returns an OptionalInt
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(Integer::max);
This is a terminal operation.
Returns  

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

min
public abstract OptionalInt min ()
Returns an OptionalInt
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(Integer::min);
This is a terminal operation.
Returns  

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

noneMatch
public abstract boolean noneMatch (IntPredicate 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 
IntPredicate : 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
public static IntStream of (int t)
Returns a sequential IntStream
containing a single element.
Parameters  

t 
int : the single element 
Returns  

IntStream 
a singleton sequential stream 
of
public static IntStream of (int... values)
Returns a sequential ordered stream whose elements are the specified values.
Parameters  

values 
int : the elements of the new stream 
Returns  

IntStream 
the new stream 
parallel
public abstract IntStream 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  

IntStream 
a parallel stream 
peek
public abstract IntStream peek (IntConsumer 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:
IntStream.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 
IntConsumer : a
noninterfering action to perform on the elements as
they are consumed from the stream 
Returns  

IntStream 
the new stream 
range
public static IntStream range (int startInclusive, int endExclusive)
Returns a sequential ordered IntStream
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 (int i = startInclusive; i < endExclusive ; i++) { ... }
Parameters  

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

IntStream 
a sequential IntStream for the range of int
elements

rangeClosed
public static IntStream rangeClosed (int startInclusive, int endInclusive)
Returns a sequential ordered IntStream
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 (int i = startInclusive; i <= endInclusive ; i++) { ... }
Parameters  

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

IntStream 
a sequential IntStream for the range of int
elements

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

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

OptionalInt 
the result of the reduction 
See also:
reduce
public abstract int reduce (int identity, IntBinaryOperator 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:
int result = identity;
for (int element : this stream)
result = accumulator.applyAsInt(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:int sum = integers.reduce(0, (a, b) > a+b);
int sum = integers.reduce(0, Integer::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 
int : the identity value for the accumulating function 
op 
IntBinaryOperator : an associative,
noninterfering,
stateless
function for combining two values 
Returns  

int 
the result of the reduction 
sequential
public abstract IntStream 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  

IntStream 
a sequential stream 
skip
public abstract IntStream 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(IntSupplier)
) 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 withsequential()
may improve performance.
Parameters  

n 
long : the number of leading elements to skip 
Returns  

IntStream 
the new stream 
Throws  

IllegalArgumentException 
if n is negative

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

IntStream 
the new stream 
spliterator
public abstract Spliterator.OfInt spliterator ()
Returns a spliterator for the elements of this stream.
This is a terminal operation.
Returns  

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

int 
the sum of elements in this stream 
summaryStatistics
public abstract IntSummaryStatistics summaryStatistics ()
Returns an IntSummaryStatistics
describing various
summary data about the elements of this stream. This is a special
case of a reduction.
This is a terminal operation.
Returns  

IntSummaryStatistics 
an IntSummaryStatistics describing various summary data
about the elements of this stream

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

int[] 
an array containing the elements of this stream 