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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.util.stream;
import java.util.Arrays;
import java.util.IntSummaryStatistics;
import java.util.Objects;
import java.util.OptionalDouble;
import java.util.OptionalInt;
import java.util.PrimitiveIterator;
import java.util.Spliterator;
import java.util.Spliterators;
import java.util.function.BiConsumer;
import java.util.function.Function;
import java.util.function.IntBinaryOperator;
import java.util.function.IntConsumer;
import java.util.function.IntFunction;
import java.util.function.IntPredicate;
import java.util.function.IntSupplier;
import java.util.function.IntToDoubleFunction;
import java.util.function.IntToLongFunction;
import java.util.function.IntUnaryOperator;
import java.util.function.ObjIntConsumer;
import java.util.function.Supplier;
/**
* A sequence of primitive int-valued elements supporting sequential and parallel
* aggregate operations. This is the {@code int} primitive specialization of
* {@link Stream}.
*
* The following example illustrates an aggregate operation using
* {@link Stream} and {@link IntStream}, computing the sum of the weights of the
* red widgets:
*
*
{@code
* int sum = widgets.stream()
* .filter(w -> w.getColor() == RED)
* .mapToInt(w -> w.getWeight())
* .sum();
* }
*
* See the class documentation for {@link Stream} and the package documentation
* for java.util.stream for additional
* specification of streams, stream operations, stream pipelines, and
* parallelism.
*
* @since 1.8
* @see Stream
* @see java.util.stream
*/
public interface IntStream extends BaseStream {
/**
* Returns a stream consisting of the elements of this stream that match
* the given predicate.
*
* This is an intermediate
* operation.
*
* @param predicate a non-interfering,
* stateless
* predicate to apply to each element to determine if it
* should be included
* @return the new stream
*/
IntStream filter(IntPredicate predicate);
/**
* Returns a stream consisting of the results of applying the given
* function to the elements of this stream.
*
*
This is an intermediate
* operation.
*
* @param mapper a non-interfering,
* stateless
* function to apply to each element
* @return the new stream
*/
IntStream map(IntUnaryOperator mapper);
/**
* Returns an object-valued {@code Stream} consisting of the results of
* applying the given function to the elements of this stream.
*
*
This is an
* intermediate operation.
*
* @param the element type of the new stream
* @param mapper a non-interfering,
* stateless
* function to apply to each element
* @return the new stream
*/
Stream mapToObj(IntFunction mapper);
/**
* Returns a {@code LongStream} consisting of the results of applying the
* given function to the elements of this stream.
*
*
This is an intermediate
* operation.
*
* @param mapper a non-interfering,
* stateless
* function to apply to each element
* @return the new stream
*/
LongStream mapToLong(IntToLongFunction mapper);
/**
* Returns a {@code DoubleStream} consisting of the results of applying the
* given function to the elements of this stream.
*
*
This is an intermediate
* operation.
*
* @param mapper a non-interfering,
* stateless
* function to apply to each element
* @return the new stream
*/
DoubleStream mapToDouble(IntToDoubleFunction 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
* {@link java.util.stream.BaseStream#close() closed} after its contents
* have been placed into this stream. (If a mapped stream is {@code null}
* an empty stream is used, instead.)
*
*
This is an intermediate
* operation.
*
* @param mapper a non-interfering,
* stateless
* function to apply to each element which produces an
* {@code IntStream} of new values
* @return the new stream
* @see Stream#flatMap(Function)
*/
IntStream flatMap(IntFunction mapper);
/**
* Returns a stream consisting of the distinct elements of this stream.
*
*
This is a stateful
* intermediate operation.
*
* @return the new stream
*/
IntStream distinct();
/**
* Returns a stream consisting of the elements of this stream in sorted
* order.
*
*
This is a stateful
* intermediate operation.
*
* @return the new stream
*/
IntStream sorted();
/**
* 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.
*
* @apiNote This method exists mainly to support debugging, where you want
* to see the elements as they flow past a certain point in a pipeline:
*
{@code
* 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();
* }
*
* @param action a
* non-interfering action to perform on the elements as
* they are consumed from the stream
* @return the new stream
*/
IntStream peek(IntConsumer action);
/**
* Returns a stream consisting of the elements of this stream, truncated
* to be no longer than {@code maxSize} in length.
*
* This is a short-circuiting
* stateful intermediate operation.
*
* @apiNote
* While {@code limit()} is generally a cheap operation on sequential
* stream pipelines, it can be quite expensive on ordered parallel pipelines,
* especially for large values of {@code maxSize}, since {@code limit(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 as {@link #generate(IntSupplier)}) or removing the
* ordering constraint with {@link #unordered()} may result in significant
* speedups of {@code limit()} 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 with
* {@code limit()} in parallel pipelines, switching to sequential execution
* with {@link #sequential()} may improve performance.
*
* @param maxSize the number of elements the stream should be limited to
* @return the new stream
* @throws IllegalArgumentException if {@code maxSize} is negative
*/
IntStream limit(long maxSize);
/**
* Returns a stream consisting of the remaining elements of this stream
* after discarding the first {@code n} elements of the stream.
* If this stream contains fewer than {@code n} elements then an
* empty stream will be returned.
*
*
This is a stateful
* intermediate operation.
*
* @apiNote
* While {@code skip()} is generally a cheap operation on sequential
* stream pipelines, it can be quite expensive on ordered parallel pipelines,
* especially for large values of {@code n}, since {@code skip(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 as {@link #generate(IntSupplier)}) or removing the
* ordering constraint with {@link #unordered()} may result in significant
* speedups of {@code skip()} 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 with
* {@code skip()} in parallel pipelines, switching to sequential execution
* with {@link #sequential()} may improve performance.
*
* @param n the number of leading elements to skip
* @return the new stream
* @throws IllegalArgumentException if {@code n} is negative
*/
IntStream skip(long n);
/**
* 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.
*
* @param action a
* non-interfering action to perform on the elements
*/
void forEach(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.
*
* @param action a
* non-interfering action to perform on the elements
* @see #forEach(IntConsumer)
*/
void forEachOrdered(IntConsumer action);
/**
* Returns an array containing the elements of this stream.
*
*
This is a terminal
* operation.
*
* @return an array containing the elements of this stream
*/
int[] toArray();
/**
* 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:
*
{@code
* int result = identity;
* for (int element : this stream)
* result = accumulator.applyAsInt(result, element)
* return result;
* }
*
* but is not constrained to execute sequentially.
*
* The {@code identity} value must be an identity for the accumulator
* function. This means that for all {@code x},
* {@code accumulator.apply(identity, x)} is equal to {@code x}.
* The {@code accumulator} function must be an
* associative function.
*
*
This is a terminal
* operation.
*
* @apiNote Sum, min, max, and average are all special cases of reduction.
* Summing a stream of numbers can be expressed as:
*
*
{@code
* int sum = integers.reduce(0, (a, b) -> a+b);
* }
*
* or more compactly:
*
* {@code
* 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.
*
* @param identity the identity value for the accumulating function
* @param op an associative,
* non-interfering,
* stateless
* function for combining two values
* @return the result of the reduction
* @see #sum()
* @see #min()
* @see #max()
* @see #average()
*/
int reduce(int identity, IntBinaryOperator op);
/**
* Performs a reduction on the
* elements of this stream, using an
* associative accumulation
* function, and returns an {@code OptionalInt} describing the reduced value,
* if any. This is equivalent to:
*
{@code
* 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 {@code accumulator} function must be an
* associative function.
*
*
This is a terminal
* operation.
*
* @param op an associative,
* non-interfering,
* stateless
* function for combining two values
* @return the result of the reduction
* @see #reduce(int, IntBinaryOperator)
*/
OptionalInt reduce(IntBinaryOperator op);
/**
* 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 {@code ArrayList}, and elements are incorporated by updating
* the state of the result rather than by replacing the result. This
* produces a result equivalent to:
*
{@code
* R result = supplier.get();
* for (int element : this stream)
* accumulator.accept(result, element);
* return result;
* }
*
* Like {@link #reduce(int, IntBinaryOperator)}, {@code collect} operations
* can be parallelized without requiring additional synchronization.
*
*
This is a terminal
* operation.
*
* @param type of the result
* @param 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.
* @param accumulator an associative,
* non-interfering,
* stateless
* function for incorporating an additional element into a result
* @param combiner an associative,
* non-interfering,
* stateless
* function for combining two values, which must be
* compatible with the accumulator function
* @return the result of the reduction
* @see Stream#collect(Supplier, BiConsumer, BiConsumer)
*/
R collect(Supplier supplier,
ObjIntConsumer accumulator,
BiConsumer combiner);
/**
* Returns the sum of elements in this stream. This is a special case
* of a reduction
* and is equivalent to:
* {@code
* return reduce(0, Integer::sum);
* }
*
* This is a terminal
* operation.
*
* @return the sum of elements in this stream
*/
int sum();
/**
* Returns an {@code 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:
*
{@code
* return reduce(Integer::min);
* }
*
* This is a terminal operation.
*
* @return an {@code OptionalInt} containing the minimum element of this
* stream, or an empty {@code OptionalInt} if the stream is empty
*/
OptionalInt min();
/**
* Returns an {@code 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:
*
{@code
* return reduce(Integer::max);
* }
*
* This is a terminal
* operation.
*
* @return an {@code OptionalInt} containing the maximum element of this
* stream, or an empty {@code OptionalInt} if the stream is empty
*/
OptionalInt max();
/**
* Returns the count of elements in this stream. This is a special case of
* a reduction and is
* equivalent to:
*
{@code
* return mapToLong(e -> 1L).sum();
* }
*
* This is a terminal operation.
*
* @return the count of elements in this stream
*/
long count();
/**
* Returns an {@code 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.
*
* @return an {@code OptionalDouble} containing the average element of this
* stream, or an empty optional if the stream is empty
*/
OptionalDouble average();
/**
* Returns an {@code IntSummaryStatistics} describing various
* summary data about the elements of this stream. This is a special
* case of a reduction.
*
*
This is a terminal
* operation.
*
* @return an {@code IntSummaryStatistics} describing various summary data
* about the elements of this stream
*/
IntSummaryStatistics summaryStatistics();
/**
* 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
* {@code false} is returned and the predicate is not evaluated.
*
*
This is a short-circuiting
* terminal operation.
*
* @apiNote
* This method evaluates the existential quantification of the
* predicate over the elements of the stream (for some x P(x)).
*
* @param predicate a non-interfering,
* stateless
* predicate to apply to elements of this stream
* @return {@code true} if any elements of the stream match the provided
* predicate, otherwise {@code false}
*/
boolean anyMatch(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 {@code true} is
* returned and the predicate is not evaluated.
*
*
This is a short-circuiting
* terminal operation.
*
* @apiNote
* 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 {@code true} (regardless of P(x)).
*
* @param predicate a non-interfering,
* stateless
* predicate to apply to elements of this stream
* @return {@code true} if either all elements of the stream match the
* provided predicate or the stream is empty, otherwise {@code false}
*/
boolean allMatch(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 {@code true} is
* returned and the predicate is not evaluated.
*
*
This is a short-circuiting
* terminal operation.
*
* @apiNote
* 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 {@code true}, regardless of P(x).
*
* @param predicate a non-interfering,
* stateless
* predicate to apply to elements of this stream
* @return {@code true} if either no elements of the stream match the
* provided predicate or the stream is empty, otherwise {@code false}
*/
boolean noneMatch(IntPredicate predicate);
/**
* Returns an {@link OptionalInt} describing the first element of this
* stream, or an empty {@code 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.
*
* @return an {@code OptionalInt} describing the first element of this stream,
* or an empty {@code OptionalInt} if the stream is empty
*/
OptionalInt findFirst();
/**
* Returns an {@link OptionalInt} describing some element of the stream, or
* an empty {@code 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 {@link #findFirst()} instead.)
*
* @return an {@code OptionalInt} describing some element of this stream, or
* an empty {@code OptionalInt} if the stream is empty
* @see #findFirst()
*/
OptionalInt findAny();
/**
* Returns a {@code LongStream} consisting of the elements of this stream,
* converted to {@code long}.
*
*
This is an intermediate
* operation.
*
* @return a {@code LongStream} consisting of the elements of this stream,
* converted to {@code long}
*/
LongStream asLongStream();
/**
* Returns a {@code DoubleStream} consisting of the elements of this stream,
* converted to {@code double}.
*
*
This is an intermediate
* operation.
*
* @return a {@code DoubleStream} consisting of the elements of this stream,
* converted to {@code double}
*/
DoubleStream asDoubleStream();
/**
* Returns a {@code Stream} consisting of the elements of this stream,
* each boxed to an {@code Integer}.
*
*
This is an intermediate
* operation.
*
* @return a {@code Stream} consistent of the elements of this stream,
* each boxed to an {@code Integer}
*/
Stream boxed();
@Override
IntStream sequential();
@Override
IntStream parallel();
@Override
PrimitiveIterator.OfInt iterator();
@Override
Spliterator.OfInt spliterator();
// Static factories
/**
* Returns a builder for an {@code IntStream}.
*
* @return a stream builder
*/
public static Builder builder() {
return new Streams.IntStreamBuilderImpl();
}
/**
* Returns an empty sequential {@code IntStream}.
*
* @return an empty sequential stream
*/
public static IntStream empty() {
return StreamSupport.intStream(Spliterators.emptyIntSpliterator(), false);
}
/**
* Returns a sequential {@code IntStream} containing a single element.
*
* @param t the single element
* @return a singleton sequential stream
*/
public static IntStream of(int t) {
return StreamSupport.intStream(new Streams.IntStreamBuilderImpl(t), false);
}
/**
* Returns a sequential ordered stream whose elements are the specified values.
*
* @param values the elements of the new stream
* @return the new stream
*/
public static IntStream of(int... values) {
return Arrays.stream(values);
}
/**
* Returns an infinite sequential ordered {@code IntStream} produced by iterative
* application of a function {@code f} to an initial element {@code seed},
* producing a {@code Stream} consisting of {@code seed}, {@code f(seed)},
* {@code f(f(seed))}, etc.
*
* The first element (position {@code 0}) in the {@code IntStream} will be
* the provided {@code seed}. For {@code n > 0}, the element at position
* {@code n}, will be the result of applying the function {@code f} to the
* element at position {@code n - 1}.
*
* @param seed the initial element
* @param f a function to be applied to to the previous element to produce
* a new element
* @return A new sequential {@code IntStream}
*/
public static IntStream iterate(final int seed, final IntUnaryOperator f) {
Objects.requireNonNull(f);
final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() {
int t = seed;
@Override
public boolean hasNext() {
return true;
}
@Override
public int nextInt() {
int v = t;
t = f.applyAsInt(t);
return v;
}
};
return StreamSupport.intStream(Spliterators.spliteratorUnknownSize(
iterator,
Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false);
}
/**
* Returns an infinite sequential unordered stream where each element is
* generated by the provided {@code IntSupplier}. This is suitable for
* generating constant streams, streams of random elements, etc.
*
* @param s the {@code IntSupplier} for generated elements
* @return a new infinite sequential unordered {@code IntStream}
*/
public static IntStream generate(IntSupplier s) {
Objects.requireNonNull(s);
return StreamSupport.intStream(
new StreamSpliterators.InfiniteSupplyingSpliterator.OfInt(Long.MAX_VALUE, s), false);
}
/**
* Returns a sequential ordered {@code IntStream} from {@code startInclusive}
* (inclusive) to {@code endExclusive} (exclusive) by an incremental step of
* {@code 1}.
*
* @apiNote
*
An equivalent sequence of increasing values can be produced
* sequentially using a {@code for} loop as follows:
*
{@code
* for (int i = startInclusive; i < endExclusive ; i++) { ... }
* }
*
* @param startInclusive the (inclusive) initial value
* @param endExclusive the exclusive upper bound
* @return a sequential {@code IntStream} for the range of {@code int}
* elements
*/
public static IntStream range(int startInclusive, int endExclusive) {
if (startInclusive >= endExclusive) {
return empty();
} else {
return StreamSupport.intStream(
new Streams.RangeIntSpliterator(startInclusive, endExclusive, false), false);
}
}
/**
* Returns a sequential ordered {@code IntStream} from {@code startInclusive}
* (inclusive) to {@code endInclusive} (inclusive) by an incremental step of
* {@code 1}.
*
* @apiNote
* An equivalent sequence of increasing values can be produced
* sequentially using a {@code for} loop as follows:
*
{@code
* for (int i = startInclusive; i <= endInclusive ; i++) { ... }
* }
*
* @param startInclusive the (inclusive) initial value
* @param endInclusive the inclusive upper bound
* @return a sequential {@code IntStream} for the range of {@code int}
* elements
*/
public static IntStream rangeClosed(int startInclusive, int endInclusive) {
if (startInclusive > endInclusive) {
return empty();
} else {
return StreamSupport.intStream(
new Streams.RangeIntSpliterator(startInclusive, endInclusive, true), false);
}
}
/**
* 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.
*
* @implNote
* Use caution when constructing streams from repeated concatenation.
* Accessing an element of a deeply concatenated stream can result in deep
* call chains, or even {@code StackOverflowException}.
*
* @param a the first stream
* @param b the second stream
* @return the concatenation of the two input streams
*/
public static IntStream concat(IntStream a, IntStream b) {
Objects.requireNonNull(a);
Objects.requireNonNull(b);
Spliterator.OfInt split = new Streams.ConcatSpliterator.OfInt(
a.spliterator(), b.spliterator());
IntStream stream = StreamSupport.intStream(split, a.isParallel() || b.isParallel());
return stream.onClose(Streams.composedClose(a, b));
}
/**
* A mutable builder for an {@code IntStream}.
*
* A stream builder has a lifecycle, which starts in a building
* phase, during which elements can be added, and then transitions to a built
* phase, after which elements may not be added. The built phase
* begins when the {@link #build()} method is called, which creates an
* ordered stream whose elements are the elements that were added to the
* stream builder, in the order they were added.
*
* @see IntStream#builder()
* @since 1.8
*/
public interface Builder extends IntConsumer {
/**
* Adds an element to the stream being built.
*
* @throws IllegalStateException if the builder has already transitioned
* to the built state
*/
@Override
void accept(int t);
/**
* Adds an element to the stream being built.
*
* @implSpec
* The default implementation behaves as if:
*
{@code
* accept(t)
* return this;
* }
*
* @param t the element to add
* @return {@code this} builder
* @throws IllegalStateException if the builder has already transitioned
* to the built state
*/
default Builder add(int t) {
accept(t);
return this;
}
/**
* Builds the stream, transitioning this builder to the built state.
* An {@code IllegalStateException} is thrown if there are further
* attempts to operate on the builder after it has entered the built
* state.
*
* @return the built stream
* @throws IllegalStateException if the builder has already transitioned to
* the built state
*/
IntStream build();
}
}