IntStream

public interface IntStream implements BaseStream<Integer, 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

Nested Class Summary

interface IntStream.Builder A mutable builder for an IntStream. 

Public Method Summary

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 DoubleStream consisting of the elements of this stream, converted to double.
abstract LongStream
asLongStream()
Returns a LongStream consisting of the elements of this stream, converted to long.
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<Integer>
boxed()
Returns a Stream consisting of the elements of this stream, each boxed to an Integer.
static IntStream.Builder
builder()
Returns a builder for an IntStream.
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.
static IntStream
empty()
Returns an empty sequential IntStream.
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 OptionalInt describing some element of the stream, or an empty OptionalInt if the stream is empty.
abstract OptionalInt
findFirst()
Returns an OptionalInt describing the first element of this stream, or an empty OptionalInt if the stream is empty.
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 IntSupplier.
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.
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 maxSize in length.
abstract IntStream
map(IntUnaryOperator mapper)
Returns a stream consisting of the results of applying the given function to the elements of this stream.
abstract DoubleStream
mapToDouble(IntToDoubleFunction mapper)
Returns a DoubleStream consisting of the results of applying the given function to the elements of this stream.
abstract LongStream
mapToLong(IntToLongFunction mapper)
Returns a LongStream consisting of the results of applying the given function to the elements of this stream.
abstract <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.
abstract OptionalInt
max()
Returns an OptionalInt describing the maximum element of this stream, or an empty optional if this stream is empty.
abstract OptionalInt
min()
Returns an OptionalInt describing the minimum element of this stream, or an empty optional if this stream is empty.
abstract boolean
noneMatch(IntPredicate predicate)
Returns whether no elements of this stream match the provided predicate.
static IntStream
of(int t)
Returns a sequential IntStream containing a single element.
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 IntStream from startInclusive (inclusive) to endExclusive (exclusive) by an incremental step of 1.
static IntStream
rangeClosed(int startInclusive, int endInclusive)
Returns a sequential ordered IntStream from startInclusive (inclusive) to endInclusive (inclusive) by an incremental step of 1.
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.
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 n elements of the stream.
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 IntSummaryStatistics describing various summary data about the elements of this stream.
abstract int[]
toArray()
Returns an array containing the elements of this stream.

Inherited Method Summary

Public Methods

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.

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, otherwise false

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.

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, otherwise false

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 to double

public abstract LongStream asLongStream ()

Returns a LongStream consisting of the elements of this stream, converted to long.

This is an intermediate operation.

Returns
  • a LongStream consisting of the elements of this stream, converted to long

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<Integer> boxed ()

Returns a Stream consisting of the elements of this stream, each boxed to an Integer.

This is an intermediate operation.

Returns
  • a Stream consistent of the elements of this stream, each boxed to an Integer

public static IntStream.Builder builder ()

Returns a builder for an IntStream.

Returns
  • a stream builder

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, IntBinaryOperator), 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
See Also

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.

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 mapToLong(e -> 1L).sum();

This is a terminal operation.

Returns
  • the count of elements in this stream

public abstract IntStream distinct ()

Returns a stream consisting of the distinct elements of this stream.

This is a stateful intermediate operation.

Returns
  • the new stream

public static IntStream empty ()

Returns an empty sequential IntStream.

Returns
  • an empty sequential stream

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 a non-interfering, stateless predicate to apply to each element to determine if it should be included
Returns
  • the new stream

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
  • an OptionalInt describing some element of this stream, or an empty OptionalInt if the stream is empty
See Also

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
  • an OptionalInt describing the first element of this stream, or an empty OptionalInt if the stream is empty

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 a non-interfering, stateless function to apply to each element which produces an IntStream of new values
Returns
  • the new stream
See Also

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 a non-interfering action to perform on the elements

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 a non-interfering action to perform on the elements
See Also

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 the IntSupplier for generated elements
Returns
  • a new infinite sequential unordered IntStream

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.

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 IntStream

public abstract PrimitiveIterator.OfInt iterator ()

Returns an iterator for the elements of this stream.

This is a terminal operation.

Returns
  • the element iterator for this stream

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.

Parameters
maxSize the number of elements the stream should be limited to
Returns
  • the new stream
Throws
IllegalArgumentException if maxSize is negative

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 a non-interfering, stateless function to apply to each element
Returns
  • the new stream

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 a non-interfering, stateless function to apply to each element
Returns
  • the new stream

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 a non-interfering, stateless function to apply to each element
Returns
  • the new stream

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 a non-interfering, stateless function to apply to each element
Returns
  • the new stream

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
  • an OptionalInt containing the maximum element of this stream, or an empty OptionalInt if the stream is empty

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
  • an OptionalInt containing the minimum element of this stream, or an empty OptionalInt if the stream is empty

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.

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, otherwise false

public static IntStream of (int t)

Returns a sequential IntStream containing a single element.

Parameters
t the single element
Returns
  • a singleton sequential stream

public static IntStream of (int... 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 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
  • a parallel stream

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.

Parameters
action a non-interfering action to perform on the elements as they are consumed from the stream
Returns
  • the new stream

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.

Parameters
startInclusive the (inclusive) initial value
endExclusive the exclusive upper bound
Returns
  • a sequential IntStream for the range of int elements

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.

Parameters
startInclusive the (inclusive) initial value
endInclusive the inclusive upper bound
Returns
  • a sequential IntStream for the range of int elements

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 an associative, non-interfering, stateless function for combining two values
Returns
  • the result of the reduction
See Also

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.

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
See Also

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
  • a sequential stream

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.

Parameters
n the number of leading elements to skip
Returns
  • the new stream
Throws
IllegalArgumentException if n is negative

public abstract IntStream 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.OfInt spliterator ()

Returns a spliterator for the elements of this stream.

This is a terminal operation.

Returns
  • the element spliterator for this stream

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
  • the sum of elements in this stream

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
  • an IntSummaryStatistics describing various summary data about the elements of this stream

public abstract int[] toArray ()

Returns an array containing the elements of this stream.

This is a terminal operation.

Returns
  • an array containing the elements of this stream