Spec-Zone .ru
спецификации, руководства, описания, API
|
public interface IntStream
filter
and map
, and terminal
operations (consuming the contents of a stream to produce a result or
side-effect), such as forEach
, findFirst
, and iterator
. Once an operation has been performed on a stream, it
is considered consumed and no longer usable for other operations.
For sequential stream pipelines, all operations are performed in the encounter order of the pipeline source, if the pipeline source has a defined encounter order.
For parallel stream pipelines, unless otherwise specified, intermediate
stream operations preserve the
encounter order of their source, and terminal operations
respect the encounter order of their source, if the source
has an encounter order. Provided that and parameters to stream operations
satisfy the non-interference
requirements, and excepting differences arising from the absence of
a defined encounter order, the result of a stream pipeline should be the
stable across multiple executions of the same operations on the same source.
However, the timing and thread in which side-effects occur (for those
operations which are allowed to produce side-effects, such as
forEach(IntConsumer)
), are explicitly nondeterministic for parallel
execution of stream pipelines.
Unless otherwise noted, passing a null
argument to any stream
method may result in a NullPointerException
.
iterator()
or spliterator()
operations to
perform a controlled traversal.Modifier and Type | Method and Description |
---|---|
boolean |
allMatch(IntPredicate predicate)
Returns whether all elements of this stream match the provided predicate.
|
boolean |
anyMatch(IntPredicate predicate)
Returns whether any elements of this stream match the provided
predicate.
|
OptionalDouble |
average()
Returns an
OptionalDouble describing the average of elements of
this stream, or an empty optional if this stream is empty. |
Stream<Integer> |
boxed()
Returns a
Stream consisting of the elements of this stream,
each boxed to an Integer . |
static StreamBuilder.OfInt |
builder()
Returns a builder for an
IntStream . |
<R> R |
collect(Supplier<R> resultFactory,
ObjIntConsumer<R> accumulator,
BiConsumer<R,R> combiner)
Performs a mutable
reduction operation on the elements of this stream.
|
long |
count()
Returns the count of elements in this stream.
|
IntStream |
distinct()
Returns a stream consisting of the distinct elements of this stream.
|
DoubleStream |
doubles()
Returns a
DoubleStream consisting of the elements of this stream,
converted to double . |
static IntStream |
empty()
Returns an empty sequential
IntStream . |
IntStream |
filter(IntPredicate predicate)
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 (in the encounter order), or an empty OptionalInt if the
stream is empty. |
IntStream |
flatMap(IntFunction<? extends IntStream> mapper)
Returns a stream consisting of the results of replacing each element of
this stream with the contents of the stream produced by applying the
provided mapping function to each element.
|
void |
forEach(IntConsumer action)
Performs an action for each element of this stream.
|
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 a sequential
IntStream where each element is
generated by an IntSupplier . |
boolean |
isParallel()
Returns whether this stream, when executed, would execute in parallel
(assuming no further modification of the stream, such as appending
further intermediate operations or changing its parallelism).
|
static IntStream |
iterate(int seed,
IntUnaryOperator f)
Returns an infinite sequential
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. |
PrimitiveIterator.OfInt |
iterator()
Returns an iterator for the elements of this stream.
|
IntStream |
limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than
maxSize in length. |
LongStream |
longs()
Returns a
LongStream consisting of the elements of this stream,
converted to long . |
IntStream |
map(IntUnaryOperator mapper)
Returns a stream consisting of the results of applying the given
function to the elements of this stream.
|
DoubleStream |
mapToDouble(IntToDoubleFunction mapper)
Returns a
DoubleStream consisting of the results of applying the
given function to the elements of this stream. |
LongStream |
mapToLong(IntToLongFunction mapper)
Returns a
LongStream consisting of the results of applying the
given function to the elements of this stream. |
<U> 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. |
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(IntPredicate predicate)
Returns whether no elements of this stream match the provided predicate.
|
static IntStream |
of(int... values)
Returns a sequential stream whose elements are the specified values.
|
static IntStream |
of(int t)
Returns a sequential
IntStream containing a single element. |
IntStream |
parallel()
Returns an equivalent stream that is parallel.
|
IntStream |
peek(IntConsumer consumer)
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
IntStream from startInclusive
(inclusive) to endExclusive (exclusive) by an incremental step of
1. |
static IntStream |
range(int startInclusive,
int endExclusive,
int step)
Returns a sequential
IntStream from startInclusive
(inclusive) to endExclusive (exclusive) by a positive step . |
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. |
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.
|
IntStream |
sequential()
Returns an equivalent stream that is sequential.
|
IntStream |
sorted()
Returns a stream consisting of the elements of this stream in sorted
order.
|
Spliterator.OfInt |
spliterator()
Returns a spliterator for the elements of this stream.
|
IntStream |
substream(long startInclusive)
Returns a stream consisting of the remaining elements of this stream
after indexing
startInclusive elements into the stream. |
IntStream |
substream(long startInclusive,
long endExclusive)
Returns a stream consisting of the remaining elements of this stream
after indexing
startInclusive elements into the stream and
truncated to contain no more than endExclusive - startInclusive
elements. |
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. |
int[] |
toArray()
Returns an array containing the elements of this stream.
|
S |
unordered()
Returns an equivalent stream that is
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)
This is an intermediate operation.
flatMap()
operation has the effect of applying a one-to-many
tranformation to the elements of the stream, and then flattening the
resulting elements into a new stream. For example, if orders
is a stream of purchase orders, and each purchase order contains a
collection of line items, then the following produces a stream of line
items:
orderStream.flatMap(order -> order.getLineItems().stream())...
mapper
- a
non-interfering, stateless function to apply to
each element which produces an IntStream
of new
valuesStream.flatMap(Function)
IntStream distinct()
This is a stateful intermediate operation.
IntStream sorted()
This is a stateful intermediate operation.
IntStream peek(IntConsumer consumer)
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.
list.stream()
.filter(filteringFunction)
.peek(e -> {System.out.println("Filtered value: " + e); });
.map(mappingFunction)
.peek(e -> {System.out.println("Mapped value: " + e); });
.collect(Collectors.toIntSummaryStastistics());
consumer
- a
non-interfering action to perform on the elements as
they are consumed from the streamIntStream limit(long maxSize)
maxSize
in length.
maxSize
- the number of elements the stream should be limited toIllegalArgumentException
- if maxSize
is negativeIntStream substream(long startInclusive)
startInclusive
elements into the stream. If the
startInclusive
index lies past the end of this stream then an
empty stream will be returned.
This is a stateful intermediate operation.
startInclusive
- the number of leading elements to skipIllegalArgumentException
- if startInclusive
is negativeIntStream substream(long startInclusive, long endExclusive)
startInclusive
elements into the stream and
truncated to contain no more than endExclusive - startInclusive
elements. If the startInclusive
index lies past the end
of this stream then an empty stream will be returned.
startInclusive
- the starting position of the substream, inclusiveendExclusive
- the ending position of the substream, exclusiveIllegalArgumentException
- if startInclusive
or
endExclusive
is negative or startInclusive
is greater
than endExclusive
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 elementsforEach(IntConsumer)
int[] toArray()
This is a terminal operation.
int reduce(int identity, IntBinaryOperator op)
int result = identity;
for (int element : this stream)
result = accumulator.apply(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 valuessum()
,
min()
,
max()
,
average()
OptionalInt 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.apply(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 valuesreduce(int, IntBinaryOperator)
<R> R collect(Supplier<R> resultFactory, 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 = resultFactory.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
- type of the resultresultFactory
- a function that creates a new result container.
For a parallel execution, this function may be
called multiple times and must return a fresh value
each time.accumulator
- an associative
non-interfering,
stateless function for incorporating an additional
element into a resultcombiner
- an associative
non-interfering,
stateless function for combining two values, which
must be compatible with the accumulator functionStream.collect(Supplier, BiConsumer, BiConsumer)
int sum()
return reduce(0, Integer::sum);
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.
OptionalDouble average()
OptionalDouble
describing the average of elements of
this stream, or an empty optional if this stream is empty. This is a
special case of a
reduction.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.IntSummaryStatistics
describing various summary data
about the elements of this streamboolean anyMatch(IntPredicate predicate)
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)
This is a short-circuiting terminal operation.
predicate
- a non-interfering,
stateless predicate to apply to elements of this
streamtrue
if all elements of the stream match the provided
predicate otherwise false
boolean noneMatch(IntPredicate predicate)
This is a short-circuiting terminal operation.
predicate
- a non-interfering,
stateless predicate to apply to elements of this
streamtrue
if no elements of the stream match the provided
predicate otherwise false
OptionalInt findFirst()
OptionalInt
describing the first element of this
stream (in the encounter order), or an empty OptionalInt
if the
stream is empty. If the stream has no encounter order, than 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 the first element
in the encounter order is desired, use findFirst()
instead.)
OptionalInt
describing some element of this stream, or
an empty OptionalInt
if the stream is emptyfindFirst()
LongStream longs()
LongStream
consisting of the elements of this stream,
converted to long
.LongStream
consisting of the elements of this stream,
converted to long
DoubleStream doubles()
DoubleStream
consisting of the elements of this stream,
converted to double
.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
.Stream
consistent of the elements of this stream,
each boxed to an Integer
IntStream sequential()
This is an intermediate operation.
IntStream parallel()
This is an intermediate operation.
PrimitiveIterator.OfInt iterator()
This is a terminal operation.
Spliterator.OfInt spliterator()
This is a terminal operation.
static StreamBuilder.OfInt 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
.
seed
- the initial elementf
- a function to be applied to to the previous element to produce
a new elementIntStream
static IntStream generate(IntSupplier s)
IntStream
where each element is
generated by an 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.
intRange(startInclusive, endExclusive, 1);
startInclusive
- the (inclusive) initial valueendExclusive
- the exclusive upper boundIntStream
for the range of int
elementsstatic IntStream range(int startInclusive, int endExclusive, int step)
IntStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by a positive step
. If startInclusive
is greater than or equal to endExclusive
, an empty stream is returned.
An equivalent sequence of increasing values can be produced
sequentially using a for
loop as follows:
for (int i = startInclusive; i < endExclusive ; i += step) { ... }
startInclusive
- the (inclusive) initial valueendExclusive
- the exclusive upper boundstep
- the positive difference between consecutive valuesIntStream
for the range of int
elementsIllegalArgumentException
- if step
is less than or equal to
0boolean isParallel()
true
if this stream would execute in parallel if executed
without further modification otherwise false
S unordered()
This is an intermediate operation.
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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