AutoCloseable
, BaseStream<Integer,IntStream>
public interface IntStream extends BaseStream<Integer,IntStream>
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.Modifier and Type | Interface | Description |
---|---|---|
static interface |
IntStream.Builder |
A mutable builder for an IntStream . |
static interface |
IntStream.IntMapMultiConsumer |
Represents an operation that accepts an int -valued argument and an IntConsumer, and returns no result. |
Modifier and Type | Method | Description |
---|---|---|
boolean |
allMatch |
Returns whether all elements of this stream match the provided predicate. |
boolean |
anyMatch |
Returns whether any elements of this stream match the provided predicate. |
DoubleStream |
asDoubleStream() |
Returns a DoubleStream consisting of the elements of this stream, converted to double . |
LongStream |
asLongStream() |
Returns a LongStream consisting of the elements of this stream, converted to long . |
OptionalDouble |
average() |
Returns an OptionalDouble describing the arithmetic mean of elements of this stream, or an empty optional if this stream is empty. |
Stream |
boxed() |
Returns a Stream consisting of the elements of this stream, each boxed to an Integer . |
static IntStream.Builder |
builder() |
Returns a builder for an IntStream . |
<R> R |
collect |
Performs a mutable reduction operation on the elements of this stream. |
static IntStream |
concat |
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. |
IntStream |
distinct() |
Returns a stream consisting of the distinct elements of this stream. |
default IntStream |
dropWhile |
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 IntStream |
empty() |
Returns an empty sequential IntStream . |
IntStream |
filter |
Returns a stream consisting of the elements of this stream that match the given predicate. |
OptionalInt |
findAny() |
Returns an OptionalInt describing some element of the stream, or an empty OptionalInt if the stream is empty. |
OptionalInt |
findFirst() |
Returns an OptionalInt describing the first element of this stream, or an empty OptionalInt if the stream is empty. |
IntStream |
flatMap |
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 |
Performs an action for each element of this stream. |
void |
forEachOrdered |
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 |
Returns an infinite sequential unordered stream where each element is generated by the provided IntSupplier . |
static IntStream |
iterate |
Returns a sequential ordered IntStream produced by iterative application of the given next function to an initial element, conditioned on satisfying the given hasNext predicate. |
static IntStream |
iterate |
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. |
IntStream |
limit |
Returns a stream consisting of the elements of this stream, truncated to be no longer than maxSize in length. |
IntStream |
map |
Returns a stream consisting of the results of applying the given function to the elements of this stream. |
default IntStream |
mapMulti |
Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements. |
DoubleStream |
mapToDouble |
Returns a DoubleStream consisting of the results of applying the given function to the elements of this stream. |
LongStream |
mapToLong |
Returns a LongStream consisting of the results of applying the given function to the elements of this stream. |
<U> Stream |
mapToObj |
Returns an object-valued Stream consisting of the results of applying the given function to the elements of this stream. |
OptionalInt |
max() |
Returns an OptionalInt describing the maximum element of this stream, or an empty optional if this stream is empty. |
OptionalInt |
min() |
Returns an OptionalInt describing the minimum element of this stream, or an empty optional if this stream is empty. |
boolean |
noneMatch |
Returns whether no elements of this stream match the provided predicate. |
static IntStream |
of |
Returns a sequential IntStream containing a single element. |
static IntStream |
of |
Returns a sequential ordered stream whose elements are the specified values. |
IntStream |
peek |
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 |
Returns a sequential ordered IntStream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1 . |
static IntStream |
rangeClosed |
Returns a sequential ordered IntStream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1 . |
int |
reduce |
Performs a reduction on the elements of this stream, using the provided identity value and an associative accumulation function, and returns the reduced value. |
OptionalInt |
reduce |
Performs a reduction on the elements of this stream, using an associative accumulation function, and returns an OptionalInt describing the reduced value, if any. |
IntStream |
skip |
Returns a stream consisting of the remaining elements of this stream after discarding the first n elements of the stream. |
IntStream |
sorted() |
Returns a stream consisting of the elements of this stream in sorted order. |
int |
sum() |
Returns the sum of elements in this stream. |
IntSummaryStatistics |
summaryStatistics() |
Returns an IntSummaryStatistics describing various summary data about the elements of this stream. |
default IntStream |
takeWhile |
Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate. |
int[] |
toArray() |
Returns an array containing the elements of this stream. |
close, isParallel, iterator, onClose, parallel, sequential, spliterator, unordered
IntStream filter(IntPredicate predicate)
This is an intermediate operation.
predicate
- a non-interfering, stateless predicate to apply to each element to determine if it should be includedIntStream map(IntUnaryOperator mapper)
This is an intermediate operation.
mapper
- a non-interfering, stateless function to apply to each element<U> Stream<U> mapToObj(IntFunction<? 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 non-interfering, stateless function to apply to each elementLongStream mapToLong(IntToLongFunction mapper)
LongStream
consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation.
mapper
- a non-interfering, stateless function to apply to each elementDoubleStream mapToDouble(IntToDoubleFunction mapper)
DoubleStream
consisting of the results of applying the given function to the elements of this stream. This is an intermediate operation.
mapper
- a non-interfering, stateless function to apply to each elementIntStream flatMap(IntFunction<? extends IntStream> 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 non-interfering, stateless function to apply to each element which produces an IntStream
of new valuesdefault IntStream mapMulti(IntStream.IntMapMultiConsumer mapper)
This is an intermediate operation.
If the consumer argument is used outside the scope of its application to the mapping function, the results are undefined.
flatMap
on this stream, passing a function that behaves as follows. First, it calls the mapper function with an IntConsumer
that accumulates replacement elements into a newly created internal buffer. When the mapper function returns, it creates an IntStream
from the internal buffer. Finally, it returns this stream to flatMap
.mapper
- a non-interfering, stateless function that generates replacement elementsIntStream distinct()
This is a stateful intermediate operation.
IntStream sorted()
This is a stateful intermediate operation.
IntStream peek(IntConsumer 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.
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();
In cases where the stream implementation is able to optimize away the production of some or all the elements (such as with short-circuiting operations like findFirst
, or in the example described in count()
), the action will not be invoked for those elements.
action
- a non-interfering action to perform on the elements as they are consumed from the streamIntStream 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(IntSupplier)
) 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 BaseStream.sequential()
may improve performance.maxSize
- the number of elements the stream should be limited toIllegalArgumentException
- if maxSize
is negativeIntStream 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(IntSupplier)
) 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 BaseStream.sequential()
may improve performance.n
- the number of leading elements to skipIllegalArgumentException
- if n
is negativedefault IntStream takeWhile(IntPredicate 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).
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 as generate(IntSupplier)
) or removing the ordering constraint with BaseStream.unordered()
may result in significant speedups of takeWhile()
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 takeWhile()
in parallel pipelines, switching to sequential execution with BaseStream.sequential()
may improve performance.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 per BaseStream.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.predicate
- a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements.default IntStream dropWhile(IntPredicate 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.
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 as generate(IntSupplier)
) or removing the ordering constraint with BaseStream.unordered()
may result in significant speedups of dropWhile()
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 dropWhile()
in parallel pipelines, switching to sequential execution with BaseStream.sequential()
may improve performance.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 per BaseStream.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.predicate
- a non-interfering, stateless predicate to apply to elements to determine the longest prefix of elements.void forEach(IntConsumer 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 non-interfering action to perform on the elementsvoid forEachOrdered(IntConsumer action)
This is a terminal operation.
action
- a non-interfering action to perform on the elementsint[] toArray()
This is a terminal operation.
int reduce(int identity, IntBinaryOperator op)
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.
int sum = integers.reduce(0, (a, b) -> a+b);
or more compactly:
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.
identity
- the identity value for the accumulating functionop
- an associative, non-interfering, stateless function for combining two valuesOptionalInt reduce(IntBinaryOperator op)
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.
op
- an associative, non-interfering, stateless function for combining two values<R> R collect(Supplier<R> supplier, ObjIntConsumer<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 (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.
R
- the type of the mutable result containersupplier
- 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, non-interfering, stateless function that must fold an element into a result container.combiner
- an associative, non-interfering, 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.int sum()
return reduce(0, Integer::sum);
This is a terminal operation.
OptionalInt min()
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.
OptionalInt
containing the minimum element of this stream, or an empty OptionalInt
if the stream is emptyOptionalInt max()
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.
OptionalInt
containing the maximum element of this stream, or an empty OptionalInt
if the stream is emptylong count()
return mapToLong(e -> 1L).sum();
This is a terminal operation.
IntStream s = IntStream.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 for flatMap
or filter
operations). Thus the count is 4 and there is no need to execute the pipeline and, as a side-effect, print out the elements.OptionalDouble average()
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.
OptionalDouble
containing the average element of this stream, or an empty optional if the stream is emptyIntSummaryStatistics summaryStatistics()
IntSummaryStatistics
describing various summary data about the elements of this stream. This is a special case of a reduction. This is a terminal operation.
IntSummaryStatistics
describing various summary data about the elements of this streamboolean anyMatch(IntPredicate predicate)
false
is returned and the predicate is not evaluated. This is a short-circuiting terminal operation.
predicate
- a non-interfering, stateless predicate to apply to elements of this streamtrue
if any elements of the stream match the provided predicate, otherwise false
boolean allMatch(IntPredicate predicate)
true
is returned and the predicate is not evaluated. This is a short-circuiting terminal operation.
true
(regardless of P(x)).predicate
- a non-interfering, 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(IntPredicate predicate)
true
is returned and the predicate is not evaluated. This is a short-circuiting terminal operation.
true
, regardless of P(x).predicate
- a non-interfering, 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
OptionalInt findFirst()
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 short-circuiting terminal operation.
OptionalInt
describing the first element of this stream, or an empty OptionalInt
if the stream is emptyOptionalInt findAny()
OptionalInt
describing some element of the stream, or an empty OptionalInt
if the stream is empty. This is a short-circuiting 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.)
OptionalInt
describing some element of this stream, or an empty OptionalInt
if the stream is emptyLongStream asLongStream()
LongStream
consisting of the elements of this stream, converted to long
. This is an intermediate operation.
LongStream
consisting of the elements of this stream, converted to long
DoubleStream asDoubleStream()
DoubleStream
consisting of the elements of this stream, converted to double
. This is an intermediate operation.
DoubleStream
consisting of the elements of this stream, converted to double
Stream<Integer> boxed()
Stream
consisting of the elements of this stream, each boxed to an Integer
. This is an intermediate operation.
Stream
consistent of the elements of this stream, each boxed to an Integer
static IntStream.Builder builder()
IntStream
.static IntStream empty()
IntStream
.static IntStream of(int t)
IntStream
containing a single element.t
- the single elementstatic IntStream of(int... values)
values
- the elements of the new streamstatic IntStream iterate(int seed, IntUnaryOperator f)
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
.
The action of applying f
for one element happens-before the action of applying f
for subsequent elements. For any given element the action may be performed in whatever thread the library chooses.
seed
- the initial elementf
- a function to be applied to the previous element to produce a new elementIntStream
static IntStream iterate(int seed, IntPredicate hasNext, IntUnaryOperator next)
IntStream
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. IntStream.iterate
should produce the same sequence of elements as produced by the corresponding for-loop:
for (int index=seed; hasNext.test(index); index = next.applyAsInt(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 happens-before the action of applying the next
function to that element. The action of applying the next
function for one element happens-before 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.
seed
- the initial elementhasNext
- 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 elementIntStream
static IntStream generate(IntSupplier s)
IntSupplier
. This is suitable for generating constant streams, streams of random elements, etc.s
- the IntSupplier
for generated elementsIntStream
static IntStream range(int startInclusive, int endExclusive)
IntStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by an incremental step of 1
.An equivalent sequence of increasing values can be produced sequentially using a for
loop as follows:
for (int i = startInclusive; i < endExclusive ; i++) { ... }
startInclusive
- the (inclusive) initial valueendExclusive
- the exclusive upper boundIntStream
for the range of int
elementsstatic IntStream rangeClosed(int startInclusive, int endInclusive)
IntStream
from startInclusive
(inclusive) to endInclusive
(inclusive) by an incremental step of 1
.An equivalent sequence of increasing values can be produced sequentially using a for
loop as follows:
for (int i = startInclusive; i <= endInclusive ; i++) { ... }
startInclusive
- the (inclusive) initial valueendInclusive
- the inclusive upper boundIntStream
for the range of int
elementsstatic IntStream concat(IntStream a, IntStream b)
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.
IntStream concat = Stream.of(s1, s2, s3, s4).flatMapToInt(s -> s);
StackOverflowError
.a
- the first streamb
- the second stream
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