Spec-Zone .ru
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|
public interface LongStream
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(LongConsumer)
), 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(LongPredicate predicate)
Returns whether all elements of this stream match the provided predicate.
|
boolean |
anyMatch(LongPredicate 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<Long> |
boxed()
Returns a
Stream consisting of the elements of this stream,
each boxed to a Long . |
static StreamBuilder.OfLong |
builder()
Returns a builder for a
LongStream . |
<R> R |
collect(Supplier<R> resultFactory,
ObjLongConsumer<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.
|
LongStream |
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 LongStream |
empty()
Returns an empty sequential
LongStream . |
LongStream |
filter(LongPredicate predicate)
Returns a stream consisting of the elements of this stream that match
the given predicate.
|
OptionalLong |
findAny()
Returns an
OptionalLong describing some element of the stream, or
an empty OptionalLong if the stream is empty. |
OptionalLong |
findFirst()
Returns an
OptionalLong describing the first element of this
stream (in the encounter order), or an empty OptionalLong if the
stream is empty. |
LongStream |
flatMap(LongFunction<? extends LongStream> 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(LongConsumer action)
Performs an action for each element of this stream.
|
void |
forEachOrdered(LongConsumer action)
Performs an action for each element of this stream, guaranteeing that
each element is processed in encounter order for streams that have a
defined encounter order.
|
static LongStream |
generate(LongSupplier s)
Returns a sequential
LongStream where each element is generated
by a LongSupplier . |
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 LongStream |
iterate(long seed,
LongUnaryOperator f)
Returns an infinite sequential
LongStream produced by iterative
application of a function f to an initial element seed ,
producing a Stream consisting of seed , f(seed) ,
f(f(seed)) , etc. |
PrimitiveIterator.OfLong |
iterator()
Returns an iterator for the elements of this stream.
|
LongStream |
limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than
maxSize in length. |
LongStream |
map(LongUnaryOperator mapper)
Returns a stream consisting of the results of applying the given
function to the elements of this stream.
|
DoubleStream |
mapToDouble(LongToDoubleFunction mapper)
Returns a
DoubleStream consisting of the results of applying the
given function to the elements of this stream. |
IntStream |
mapToInt(LongToIntFunction mapper)
Returns an
IntStream consisting of the results of applying the
given function to the elements of this stream. |
<U> Stream<U> |
mapToObj(LongFunction<? extends U> mapper)
Returns an object-valued
Stream consisting of the results of
applying the given function to the elements of this stream. |
OptionalLong |
max()
Returns an
OptionalLong describing the maximum element of this
stream, or an empty optional if this stream is empty. |
OptionalLong |
min()
Returns an
OptionalLong describing the minimum element of this
stream, or an empty optional if this stream is empty. |
boolean |
noneMatch(LongPredicate predicate)
Returns whether no elements of this stream match the provided predicate.
|
static LongStream |
of(long... values)
Returns a sequential stream whose elements are the specified values.
|
static LongStream |
of(long t)
Returns a sequential
LongStream containing a single element. |
LongStream |
parallel()
Returns an equivalent stream that is parallel.
|
LongStream |
peek(LongConsumer 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 LongStream |
range(long startInclusive,
long endExclusive)
Returns a sequential
LongStream from startInclusive
(inclusive) to endExclusive (exclusive) by an incremental step of
1. |
static LongStream |
range(long startInclusive,
long endExclusive,
long step)
Returns a sequential
LongStream from startInclusive
(inclusive) to endExclusive (exclusive) by step . |
OptionalLong |
reduce(LongBinaryOperator op)
Performs a reduction on the
elements of this stream, using an
associative accumulation
function, and returns an
OptionalLong describing the reduced value,
if any. |
long |
reduce(long identity,
LongBinaryOperator op)
Performs a reduction on the
elements of this stream, using the provided identity value and an
associative
accumulation function, and returns the reduced value.
|
LongStream |
sequential()
Returns an equivalent stream that is sequential.
|
LongStream |
sorted()
Returns a stream consisting of the elements of this stream in sorted
order.
|
Spliterator.OfLong |
spliterator()
Returns a spliterator for the elements of this stream.
|
LongStream |
substream(long startInclusive)
Returns a stream consisting of the remaining elements of this stream
after indexing
startInclusive elements into the stream. |
LongStream |
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. |
long |
sum()
Returns the sum of elements in this stream.
|
LongSummaryStatistics |
summaryStatistics()
Returns a
LongSummaryStatistics describing various summary data
about the elements of this stream. |
long[] |
toArray()
Returns an array containing the elements of this stream.
|
S |
unordered()
Returns an equivalent stream that is
unordered.
|
LongStream filter(LongPredicate predicate)
This is an intermediate operation.
predicate
- a
non-interfering, stateless predicate to apply to
each element to determine if it should be includedLongStream map(LongUnaryOperator mapper)
This is an intermediate operation.
mapper
- a
non-interfering, stateless function to apply to each
element<U> Stream<U> mapToObj(LongFunction<? 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
elementIntStream mapToInt(LongToIntFunction mapper)
IntStream
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(LongToDoubleFunction 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
elementLongStream flatMap(LongFunction<? extends LongStream> 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 LongStream
of new
valuesStream.flatMap(Function)
LongStream distinct()
This is a stateful intermediate operation.
LongStream sorted()
This is a stateful intermediate operation.
LongStream peek(LongConsumer 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.toLongSummaryStastistics());
consumer
- a
non-interfering action to perform on the elements as
they are consumed from the streamLongStream limit(long maxSize)
maxSize
in length.
maxSize
- the number of elements the stream should be limited toIllegalArgumentException
- if maxSize
is negativeLongStream 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 negativeLongStream 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(LongConsumer 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(LongConsumer action)
This is a terminal operation.
action
- a
non-interfering action to perform on the elementsforEach(LongConsumer)
long[] toArray()
This is a terminal operation.
long reduce(long identity, LongBinaryOperator op)
long result = identity;
for (long 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.
long sum = integers.reduce(0, (a, b) -> a+b);
or more compactly:
long sum = integers.reduce(0, Long::sum);
While this may seem a more roundabout way to perform an aggregation compared to simply mutating a running total in a loop, reduction operations parallelize more gracefully, without needing additional synchronization and with greatly reduced risk of data races.
identity
- the identity value for the accumulating functionop
- an associative
non-interfering,
stateless function for combining two valuessum()
,
min()
,
max()
,
average()
OptionalLong reduce(LongBinaryOperator op)
OptionalLong
describing the reduced value,
if any. This is equivalent to:
boolean foundAny = false;
long result = null;
for (long element : this stream) {
if (!foundAny) {
foundAny = true;
result = element;
}
else
result = accumulator.apply(result, element);
}
return foundAny ? OptionalLong.of(result) : OptionalLong.empty();
but is not constrained to execute sequentially.
The accumulator
function must be an
associative function.
This is a terminal operation.
op
- an associative
non-interfering,
stateless function for combining two valuesreduce(long, LongBinaryOperator)
<R> R collect(Supplier<R> resultFactory, ObjLongConsumer<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 (long element : this stream)
accumulator.accept(result, element);
return result;
Like reduce(long, LongBinaryOperator)
, collect
operations
can be parallelized without requiring additional synchronization.
This is a terminal operation.
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)
long sum()
return reduce(0, Long::sum);
OptionalLong min()
OptionalLong
describing the minimum element of this
stream, or an empty optional if this stream is empty. This is a special
case of a reduction
and is equivalent to:
return reduce(Long::min);
This is a terminal operation.
OptionalLong
containing the minimum element of this
stream, or an empty OptionalLong
if the stream is emptyOptionalLong max()
OptionalLong
describing the maximum element of this
stream, or an empty optional if this stream is empty. This is a special
case of a reduction
and is equivalent to:
return reduce(Long::max);
This is a terminal operation.
OptionalLong
containing the maximum element of this
stream, or an empty OptionalLong
if the stream is emptylong count()
return map(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 emptyLongSummaryStatistics summaryStatistics()
LongSummaryStatistics
describing various summary data
about the elements of this stream. This is a special case of a
reduction.LongSummaryStatistics
describing various summary data
about the elements of this streamboolean anyMatch(LongPredicate 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(LongPredicate 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(LongPredicate 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
OptionalLong findFirst()
OptionalLong
describing the first element of this
stream (in the encounter order), or an empty OptionalLong
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.
OptionalLong
describing the first element of this
stream, or an empty OptionalLong
if the stream is emptyOptionalLong findAny()
OptionalLong
describing some element of the stream, or
an empty OptionalLong
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.)
OptionalLong
describing some element of this stream,
or an empty OptionalLong
if the stream is emptyfindFirst()
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<Long> boxed()
Stream
consisting of the elements of this stream,
each boxed to a Long
.Stream
consistent of the elements of this stream,
each boxed to Long
LongStream sequential()
This is an intermediate operation.
LongStream parallel()
This is an intermediate operation.
PrimitiveIterator.OfLong iterator()
This is a terminal operation.
Spliterator.OfLong spliterator()
This is a terminal operation.
static StreamBuilder.OfLong builder()
LongStream
.static LongStream empty()
LongStream
.static LongStream of(long t)
LongStream
containing a single element.t
- the single elementstatic LongStream of(long... values)
values
- the elements of the new streamstatic LongStream iterate(long seed, LongUnaryOperator f)
LongStream
produced by iterative
application of a function f
to an initial element seed
,
producing a Stream
consisting of seed
, f(seed)
,
f(f(seed))
, etc.
The first element (position 0
) in the LongStream
will
be the provided seed
. For n > 0
, the element at position
n
, will be the result of applying the function f
to the
element at position n - 1
.
seed
- the initial elementf
- a function to be applied to to the previous element to produce
a new elementLongStream
static LongStream generate(LongSupplier s)
LongStream
where each element is generated
by a LongSupplier
. This is suitable for generating constant
streams, streams of random elements, etc.s
- the LongSupplier
for generated elementsLongStream
static LongStream range(long startInclusive, long endExclusive)
LongStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by an incremental step of
1.
longRange(startInclusive, endExclusive, 1);
startInclusive
- the (inclusive) initial valueendExclusive
- the exclusive upper boundLongStream
for the range of long
elementsstatic LongStream range(long startInclusive, long endExclusive, long step)
LongStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by 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 (long i = startInclusive; i < endExclusive ; i += step) { ... }
startInclusive
- the (inclusive) initial valueendExclusive
- the exclusive upper boundstep
- the difference between consecutive valuesLongStream
for the range of long
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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