IntStream
public
interface
IntStream
implements
BaseStream<Integer, IntStream>
java.util.stream.IntStream |
A sequence of primitive int-valued 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 |
interface |
IntStream.IntMapMultiConsumer
Represents an operation that accepts 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. |
default
IntStream
|
dropWhile(IntPredicate predicate)
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 |
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 |
static
IntStream
|
iterate(int seed, IntPredicate hasNext, IntUnaryOperator next)
Returns a 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. |
default
IntStream
|
mapMulti(IntStream.IntMapMultiConsumer mapper)
Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements. |
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 object-valued |
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 |
default
IntStream
|
takeWhile(IntPredicate predicate)
Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate. |
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 short-circuiting 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 non-interfering,
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 short-circuiting 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 non-interfering,
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, java.util.function.IntBinaryOperator)
, collect
operations
can be parallelized without requiring additional synchronization.
This is a terminal operation.
Parameters | |
---|---|
supplier |
Supplier : 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 |
ObjIntConsumer : an associative,
non-interfering,
stateless
function that must fold an element into a result
container. |
combiner |
BiConsumer : 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. |
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.
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.
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
StackOverflowError
.
API Note:
- To preserve optimization opportunities this method binds each stream to
its source and accepts only two streams as parameters. For example, the
exact size of the concatenated stream source can be computed if the exact
size of each input stream source is known.
To concatenate more streams without binding, or without nested calls to
this method, try creating a stream of streams and flat-mapping with the
identity function, for example:
IntStream concat = Stream.of(s1, s2, s3, s4).flatMapToInt(s -> s);
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.
API Note:
- An implementation may choose to not execute the stream pipeline (either
sequentially or in parallel) if it is capable of computing the count
directly from the stream source. In such cases no source elements will
be traversed and no intermediate operations will be evaluated.
Behavioral parameters with side-effects, which are strongly discouraged
except for harmless cases such as debugging, may be affected. For
example, consider the following stream:
The number of elements covered by the stream source is known and the intermediate operation,IntStream s = IntStream.of(1, 2, 3, 4); long count = s.peek(System.out::println).count();
peek
, does not inject into or remove elements from the stream (as may be the case forflatMap
orfilter
operations). Thus the count is 4 and there is no need to execute the pipeline and, as a side-effect, print out the elements.
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 |
dropWhile
public IntStream dropWhile (IntPredicate predicate)
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. Otherwise returns, if this stream is unordered, a stream consisting of the remaining elements of this stream after dropping a subset of elements that match the given 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.
Implementation Requirements:
- The default implementation obtains the
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 perBaseStream.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.
API Note:
- While
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 asgenerate(java.util.function.IntSupplier)
) or removing the ordering constraint withBaseStream.unordered()
may result in significant speedups ofdropWhile()
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 withdropWhile()
in parallel pipelines, switching to sequential execution withsequential()
may improve performance.
Parameters | |
---|---|
predicate |
IntPredicate : a non-interfering,
stateless
predicate to apply to elements to determine the longest
prefix of elements. |
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 non-interfering,
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 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.)
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 short-circuiting 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 non-interfering,
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
non-interfering 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
non-interfering 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
.
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.
Parameters | |
---|---|
seed |
int : the initial element |
f |
IntUnaryOperator : a function to be applied to the previous element to produce
a new element |
Returns | |
---|---|
IntStream |
a new sequential IntStream |
iterate
public static IntStream iterate (int seed, IntPredicate hasNext, IntUnaryOperator next)
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. 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.
Parameters | |
---|---|
seed |
int : the initial element |
hasNext |
IntPredicate : a predicate to apply to elements to determine when the
stream must terminate. |
next |
IntUnaryOperator : a function to be applied 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 short-circuiting 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(java.util.function.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 non-interfering,
stateless
function to apply to each element |
Returns | |
---|---|
IntStream |
the new stream |
mapMulti
public IntStream mapMulti (IntStream.IntMapMultiConsumer mapper)
Returns a stream consisting of the results of replacing each element of this stream with multiple elements, specifically zero or more elements. Replacement is performed by applying the provided mapping function to each element in conjunction with a consumer argument that accepts replacement elements. The mapping function calls the consumer zero or more times to provide the replacement elements.
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.
Implementation Requirements:
- The default implementation invokes
flatMap
on this stream, passing a function that behaves as follows. First, it calls the mapper function with anIntConsumer
that accumulates replacement elements into a newly created internal buffer. When the mapper function returns, it creates anIntStream
from the internal buffer. Finally, it returns this stream toflatMap
.
Parameters | |
---|---|
mapper |
IntStream.IntMapMultiConsumer : a non-interfering,
stateless
function that generates replacement elements |
Returns | |
---|---|
IntStream |
the new stream |
See also:
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 non-interfering,
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 non-interfering,
stateless
function to apply to each element |
Returns | |
---|---|
LongStream |
the new stream |
mapToObj
public abstract Stream<U> mapToObj (IntFunction<? extends U> mapper)
Returns an object-valued 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 non-interfering,
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 short-circuiting 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 non-interfering,
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();
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 incount()
), the action will not be invoked for those elements.
Parameters | |
---|---|
action |
IntConsumer : a
non-interfering 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,
non-interfering,
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 and max are all special cases of reduction that can be
expressed using this method.
For example, summing a stream 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,
non-interfering,
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(java.util.function.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.
The returned spliterator should report the set of characteristics derived from the stream pipeline (namely the characteristics derived from the stream source spliterator and the intermediate operations). Implementations may report a sub-set of those characteristics. For example, it may be too expensive to compute the entire set for some or all possible stream pipelines.
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 |
takeWhile
public IntStream takeWhile (IntPredicate predicate)
Returns, if this stream is ordered, a stream consisting of the longest prefix of elements taken from this stream that match the given predicate. Otherwise returns, if this stream is unordered, a stream consisting of a subset of elements taken from this stream that match the given 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).
This is a short-circuiting stateful intermediate operation.
Implementation Requirements:
- The default implementation obtains the
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 perBaseStream.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.
API Note:
- While
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 asgenerate(java.util.function.IntSupplier)
) or removing the ordering constraint withBaseStream.unordered()
may result in significant speedups oftakeWhile()
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 withtakeWhile()
in parallel pipelines, switching to sequential execution withsequential()
may improve performance.
Parameters | |
---|---|
predicate |
IntPredicate : a non-interfering,
stateless
predicate to apply to elements to determine the longest
prefix of elements. |
Returns | |
---|---|
IntStream |
the new 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 |
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Last updated 2024-06-18 UTC.