A sequence of primitive long-valued elements supporting sequential and parallel
aggregate operations. This is the long
primitive specialization of
Stream
.
The following example illustrates an aggregate operation using
Stream
and LongStream
, computing the sum of the weights of the
red widgets:
long sum = widgets.stream()
.filter(w -> w.getColor() == RED)
.mapToLong(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
Nested Class Summary
interface | LongStream.Builder | A mutable builder for a LongStream . |
Public Method Summary
abstract boolean |
allMatch(LongPredicate predicate)
Returns whether all elements of this stream match the provided predicate.
|
abstract boolean |
anyMatch(LongPredicate predicate)
Returns whether any elements of this stream match the provided
predicate.
|
abstract DoubleStream |
asDoubleStream()
Returns a
DoubleStream consisting of the elements of this stream,
converted to double . |
abstract OptionalDouble |
average()
Returns an
OptionalDouble describing the arithmetic mean of elements of
this stream, or an empty optional if this stream is empty. |
abstract Stream<Long> |
boxed()
Returns a
Stream consisting of the elements of this stream,
each boxed to a Long . |
static LongStream.Builder |
builder()
Returns a builder for a
LongStream . |
abstract <R> R |
collect(Supplier<R> supplier, ObjLongConsumer<R> accumulator, BiConsumer<R, R> combiner)
Performs a mutable
reduction operation on the elements of this stream.
|
static LongStream |
concat(LongStream a, LongStream 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 LongStream |
distinct()
Returns a stream consisting of the distinct elements of this stream.
|
static LongStream |
empty()
Returns an empty sequential
LongStream . |
abstract LongStream |
filter(LongPredicate predicate)
Returns a stream consisting of the elements of this stream that match
the given predicate.
|
abstract OptionalLong |
findAny()
Returns an
OptionalLong describing some element of the stream, or
an empty OptionalLong if the stream is empty. |
abstract OptionalLong |
findFirst()
Returns an
OptionalLong describing the first element of this
stream, or an empty OptionalLong if the stream is empty. |
abstract LongStream |
flatMap(LongFunction<? extends LongStream> 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 | |
abstract 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 an infinite sequential unordered stream where each element is
generated by the provided
LongSupplier . |
static LongStream |
iterate(long seed, LongUnaryOperator f)
Returns an infinite sequential ordered
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. |
abstract PrimitiveIterator.OfLong |
iterator()
Returns an iterator for the elements of this stream.
|
abstract LongStream |
limit(long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than
maxSize in length. |
abstract LongStream |
map(LongUnaryOperator mapper)
Returns a stream consisting of the results of applying the given
function to the elements of this stream.
|
abstract DoubleStream |
mapToDouble(LongToDoubleFunction mapper)
Returns a
DoubleStream consisting of the results of applying the
given function to the elements of this stream. |
abstract IntStream |
mapToInt(LongToIntFunction mapper)
Returns an
IntStream consisting of the results of applying the
given function to the elements of this stream. |
abstract <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. |
abstract OptionalLong |
max()
Returns an
OptionalLong describing the maximum element of this
stream, or an empty optional if this stream is empty. |
abstract OptionalLong |
min()
Returns an
OptionalLong describing the minimum element of this
stream, or an empty optional if this stream is empty. |
abstract boolean |
noneMatch(LongPredicate predicate)
Returns whether no elements of this stream match the provided predicate.
|
static LongStream |
of(long... values)
Returns a sequential ordered stream whose elements are the specified values.
|
static LongStream |
of(long t)
Returns a sequential
LongStream containing a single element. |
abstract LongStream |
parallel()
Returns an equivalent stream that is parallel.
|
abstract LongStream |
peek(LongConsumer 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 LongStream |
range(long startInclusive, long endExclusive)
Returns a sequential ordered
LongStream from startInclusive
(inclusive) to endExclusive (exclusive) by an incremental step of
1 . |
static LongStream |
rangeClosed(long startInclusive, long endInclusive)
Returns a sequential ordered
LongStream from startInclusive
(inclusive) to endInclusive (inclusive) by an incremental step of
1 . |
abstract 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. |
abstract 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.
|
abstract LongStream |
sequential()
Returns an equivalent stream that is sequential.
|
abstract LongStream |
skip(long n)
Returns a stream consisting of the remaining elements of this stream
after discarding the first
n elements of the stream. |
abstract LongStream |
sorted()
Returns a stream consisting of the elements of this stream in sorted
order.
|
abstract Spliterator.OfLong |
spliterator()
Returns a spliterator for the elements of this stream.
|
abstract long |
sum()
Returns the sum of elements in this stream.
|
abstract LongSummaryStatistics |
summaryStatistics()
Returns a
LongSummaryStatistics describing various summary data
about the elements of this stream. |
abstract long[] |
toArray()
Returns an array containing the elements of this stream.
|
Inherited Method Summary
Public Methods
public abstract boolean allMatch (LongPredicate 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.
Parameters
predicate | a non-interfering, stateless predicate to apply to elements of this stream |
---|
Returns
true
if either all elements of the stream match the provided predicate or the stream is empty, otherwisefalse
public abstract boolean anyMatch (LongPredicate 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.
Parameters
predicate | a non-interfering, stateless predicate to apply to elements of this stream |
---|
Returns
true
if any elements of the stream match the provided predicate, otherwisefalse
public abstract DoubleStream asDoubleStream ()
Returns a DoubleStream
consisting of the elements of this stream,
converted to double
.
This is an intermediate operation.
Returns
- a
DoubleStream
consisting of the elements of this stream, converted todouble
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
- an
OptionalDouble
containing the average element of this stream, or an empty optional if the stream is empty
public abstract Stream<Long> boxed ()
Returns a Stream
consisting of the elements of this stream,
each boxed to a Long
.
This is an intermediate operation.
Returns
- a
Stream
consistent of the elements of this stream, each boxed toLong
public static LongStream.Builder builder ()
Returns a builder for a LongStream
.
Returns
- a stream builder
public abstract R collect (Supplier<R> supplier, ObjLongConsumer<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 (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.
Parameters
supplier | a function that creates a new result container. For a parallel execution, this function may be called multiple times and must return a fresh value each time. |
---|---|
accumulator | an associative, non-interfering, stateless function for incorporating an additional element into a result |
combiner | an associative, non-interfering, stateless function for combining two values, which must be compatible with the accumulator function |
Returns
- the result of the reduction
public static LongStream concat (LongStream a, LongStream 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.
Parameters
a | the first stream |
---|---|
b | the second stream |
Returns
- the concatenation of the two input streams
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 map(e -> 1L).sum();
This is a terminal operation.
Returns
- the count of elements in this stream
public abstract LongStream distinct ()
Returns a stream consisting of the distinct elements of this stream.
This is a stateful intermediate operation.
Returns
- the new stream
public static LongStream empty ()
Returns an empty sequential LongStream
.
Returns
- an empty sequential stream
public abstract LongStream filter (LongPredicate predicate)
Returns a stream consisting of the elements of this stream that match the given predicate.
This is an intermediate operation.
Parameters
predicate | a non-interfering, stateless predicate to apply to each element to determine if it should be included |
---|
Returns
- the new stream
public abstract OptionalLong findAny ()
Returns an 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 a stable result
is desired, use findFirst()
instead.)
Returns
- an
OptionalLong
describing some element of this stream, or an emptyOptionalLong
if the stream is empty
See Also
public abstract OptionalLong findFirst ()
Returns an OptionalLong
describing the first element of this
stream, or an empty OptionalLong
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
- an
OptionalLong
describing the first element of this stream, or an emptyOptionalLong
if the stream is empty
public abstract LongStream flatMap (LongFunction<? extends LongStream> 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 | a non-interfering,
stateless
function to apply to each element which produces a
LongStream of new values |
---|
Returns
- the new stream
See Also
public abstract void forEach (LongConsumer 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 | a non-interfering action to perform on the elements |
---|
public abstract 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.
This is a terminal operation.
Parameters
action | a non-interfering action to perform on the elements |
---|
See Also
public static LongStream generate (LongSupplier s)
Returns an infinite sequential unordered stream where each element is
generated by the provided LongSupplier
. This is suitable for
generating constant streams, streams of random elements, etc.
Parameters
s | the LongSupplier for generated elements |
---|
Returns
- a new infinite sequential unordered
LongStream
public static LongStream iterate (long seed, LongUnaryOperator f)
Returns an infinite sequential ordered 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
.
Parameters
seed | the initial element |
---|---|
f | a function to be applied to to the previous element to produce a new element |
Returns
- a new sequential
LongStream
public abstract PrimitiveIterator.OfLong iterator ()
Returns an iterator for the elements of this stream.
This is a terminal operation.
Returns
- the element iterator for this stream
public abstract LongStream limit (long maxSize)
Returns a stream consisting of the elements of this stream, truncated
to be no longer than maxSize
in length.
Parameters
maxSize | the number of elements the stream should be limited to |
---|
Returns
- the new stream
Throws
IllegalArgumentException | if maxSize is negative
|
---|
public abstract LongStream map (LongUnaryOperator 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 | a non-interfering, stateless function to apply to each element |
---|
Returns
- the new stream
public abstract DoubleStream mapToDouble (LongToDoubleFunction 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 | a non-interfering, stateless function to apply to each element |
---|
Returns
- the new stream
public abstract IntStream mapToInt (LongToIntFunction mapper)
Returns an IntStream
consisting of the results of applying the
given function to the elements of this stream.
This is an intermediate operation.
Parameters
mapper | a non-interfering, stateless function to apply to each element |
---|
Returns
- the new stream
public abstract 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.
This is an intermediate operation.
Parameters
mapper | a non-interfering, stateless function to apply to each element |
---|
Returns
- the new stream
public abstract OptionalLong max ()
Returns an 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.
Returns
- an
OptionalLong
containing the maximum element of this stream, or an emptyOptionalLong
if the stream is empty
public abstract OptionalLong min ()
Returns an 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.
Returns
- an
OptionalLong
containing the minimum element of this stream, or an emptyOptionalLong
if the stream is empty
public abstract boolean noneMatch (LongPredicate 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.
Parameters
predicate | a non-interfering, stateless predicate to apply to elements of this stream |
---|
Returns
true
if either no elements of the stream match the provided predicate or the stream is empty, otherwisefalse
public static LongStream of (long... values)
Returns a sequential ordered stream whose elements are the specified values.
Parameters
values | the elements of the new stream |
---|
Returns
- the new stream
public static LongStream of (long t)
Returns a sequential LongStream
containing a single element.
Parameters
t | the single element |
---|
Returns
- a singleton sequential stream
public abstract LongStream 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
- a parallel stream
public abstract LongStream peek (LongConsumer 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.
Parameters
action | a non-interfering action to perform on the elements as they are consumed from the stream |
---|
Returns
- the new stream
public static LongStream range (long startInclusive, long endExclusive)
Returns a sequential ordered LongStream
from startInclusive
(inclusive) to endExclusive
(exclusive) by an incremental step of
1
.
Parameters
startInclusive | the (inclusive) initial value |
---|---|
endExclusive | the exclusive upper bound |
Returns
- a sequential
LongStream
for the range oflong
elements
public static LongStream rangeClosed (long startInclusive, long endInclusive)
Returns a sequential ordered LongStream
from startInclusive
(inclusive) to endInclusive
(inclusive) by an incremental step of
1
.
Parameters
startInclusive | the (inclusive) initial value |
---|---|
endInclusive | the inclusive upper bound |
Returns
- a sequential
LongStream
for the range oflong
elements
public abstract 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. This is equivalent to:
boolean foundAny = false;
long result = null;
for (long element : this stream) {
if (!foundAny) {
foundAny = true;
result = element;
}
else
result = accumulator.applyAsLong(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.
Parameters
op | an associative, non-interfering, stateless function for combining two values |
---|
Returns
- the result of the reduction
See Also
public abstract 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. This is equivalent to:
long result = identity;
for (long element : this stream)
result = accumulator.applyAsLong(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.
Parameters
identity | the identity value for the accumulating function |
---|---|
op | an associative, non-interfering, stateless function for combining two values |
Returns
- the result of the reduction
public abstract LongStream 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
- a sequential stream
public abstract LongStream 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.
Parameters
n | the number of leading elements to skip |
---|
Returns
- the new stream
Throws
IllegalArgumentException | if n is negative
|
---|
public abstract LongStream sorted ()
Returns a stream consisting of the elements of this stream in sorted order.
This is a stateful intermediate operation.
Returns
- the new stream
public abstract Spliterator.OfLong spliterator ()
Returns a spliterator for the elements of this stream.
This is a terminal operation.
Returns
- the element spliterator for this stream
public abstract long sum ()
Returns the sum of elements in this stream. This is a special case of a reduction and is equivalent to:
return reduce(0, Long::sum);
This is a terminal operation.
Returns
- the sum of elements in this stream
public abstract LongSummaryStatistics summaryStatistics ()
Returns a LongSummaryStatistics
describing various summary data
about the elements of this stream. This is a special case of a
reduction.
This is a terminal operation.
Returns
- a
LongSummaryStatistics
describing various summary data about the elements of this stream
public abstract long[] toArray ()
Returns an array containing the elements of this stream.
This is a terminal operation.
Returns
- an array containing the elements of this stream