Java tutorial
/* * Copyright (c) 2012, 2016, 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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}. * * <p>The following example illustrates an aggregate operation using * {@link Stream} and {@link IntStream}, computing the sum of the weights of the * red widgets: * * <pre>{@code * int sum = widgets.stream() * .filter(w -> w.getColor() == RED) * .mapToInt(w -> w.getWeight()) * .sum(); * }</pre> * * See the class documentation for {@link Stream} and the package documentation * for <a href="package-summary.html">java.util.stream</a> for additional * specification of streams, stream operations, stream pipelines, and * parallelism. * * @since 1.8 * @see Stream * @see <a href="package-summary.html">java.util.stream</a> */ public interface IntStream extends BaseStream<Integer, IntStream> { /** * Returns a stream consisting of the elements of this stream that match * the given predicate. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is an <a href="package-summary.html#StreamOps"> * intermediate operation</a>. * * @param <U> the element type of the new stream * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * function to apply to each element * @return the new stream */ <U> Stream<U> mapToObj(IntFunction<? extends U> mapper); /** * Returns a {@code LongStream} consisting of the results of applying the * given function to the elements of this stream. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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.) * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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<? extends IntStream> mapper); /** * Returns a stream consisting of the distinct elements of this stream. * * <p>This is a <a href="package-summary.html#StreamOps">stateful * intermediate operation</a>. * * @return the new stream */ IntStream distinct(); /** * Returns a stream consisting of the elements of this stream in sorted * order. * * <p>This is a <a href="package-summary.html#StreamOps">stateful * intermediate operation</a>. * * @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. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * <p>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: * <pre>{@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(); * }</pre> * * <p>In cases where the stream implementation is able to optimize away the * production of some or all the elements (such as with short-circuiting * operations like {@code findFirst}, or in the example described in * {@link #count}), the action will not be invoked for those elements. * * @param action a <a href="package-summary.html#NonInterference"> * non-interfering</a> 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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * stateful intermediate operation</a>. * * @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 <em>n</em> elements, but the * <em>first n</em> 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. * * <p>This is a <a href="package-summary.html#StreamOps">stateful * intermediate operation</a>. * * @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 <em>n</em> elements, but the * <em>first n</em> 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); /** * Returns, if this stream is ordered, a stream consisting of the longest * prefix of elements taken from this stream that match the given predicate. * Otherwise returns, if this stream is unordered, a stream consisting of a * subset of elements taken from this stream that match the given predicate. * * <p>If this stream is ordered then the longest prefix is a contiguous * sequence of elements of this stream that match the given predicate. The * first element of the sequence is the first element of this stream, and * the element immediately following the last element of the sequence does * not match the given predicate. * * <p>If this stream is unordered, and some (but not all) elements of this * stream match the given predicate, then the behavior of this operation is * nondeterministic; it is free to take any subset of matching elements * (which includes the empty set). * * <p>Independent of whether this stream is ordered or unordered if all * elements of this stream match the given predicate then this operation * takes all elements (the result is the same as the input), or if no * elements of the stream match the given predicate then no elements are * taken (the result is an empty stream). * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * stateful intermediate operation</a>. * * @implSpec * The default implementation obtains the {@link #spliterator() spliterator} * of this stream, wraps that spliterator so as to support the semantics * of this operation on traversal, and returns a new stream associated with * the wrapped spliterator. The returned stream preserves the execution * characteristics of this stream (namely parallel or sequential execution * as per {@link #isParallel()}) but the wrapped spliterator may choose to * not support splitting. When the returned stream is closed, the close * handlers for both the returned and this stream are invoked. * * @apiNote * While {@code takeWhile()} is generally a cheap operation on sequential * stream pipelines, it can be quite expensive on ordered parallel * pipelines, since the operation is constrained to return not just any * valid prefix, but the longest prefix of 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 takeWhile()} 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 takeWhile()} in parallel pipelines, switching to * sequential execution with {@link #sequential()} may improve performance. * * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * predicate to apply to elements to determine the longest * prefix of elements. * @return the new stream * @since 9 */ default IntStream takeWhile(IntPredicate predicate) { Objects.requireNonNull(predicate); // Reuses the unordered spliterator, which, when encounter is present, // is safe to use as long as it configured not to split return StreamSupport .intStream(new WhileOps.UnorderedWhileSpliterator.OfInt.Taking(spliterator(), true, predicate), isParallel()) .onClose(this::close); } /** * Returns, if this stream is ordered, a stream consisting of the remaining * elements of this stream after dropping the longest prefix of elements * that match the given predicate. Otherwise returns, if this stream is * unordered, a stream consisting of the remaining elements of this stream * after dropping a subset of elements that match the given predicate. * * <p>If this stream is ordered then the longest prefix is a contiguous * sequence of elements of this stream that match the given predicate. The * first element of the sequence is the first element of this stream, and * the element immediately following the last element of the sequence does * not match the given predicate. * * <p>If this stream is unordered, and some (but not all) elements of this * stream match the given predicate, then the behavior of this operation is * nondeterministic; it is free to drop any subset of matching elements * (which includes the empty set). * * <p>Independent of whether this stream is ordered or unordered if all * elements of this stream match the given predicate then this operation * drops all elements (the result is an empty stream), or if no elements of * the stream match the given predicate then no elements are dropped (the * result is the same as the input). * * <p>This is a <a href="package-summary.html#StreamOps">stateful * intermediate operation</a>. * * @implSpec * The default implementation obtains the {@link #spliterator() spliterator} * of this stream, wraps that spliterator so as to support the semantics * of this operation on traversal, and returns a new stream associated with * the wrapped spliterator. The returned stream preserves the execution * characteristics of this stream (namely parallel or sequential execution * as per {@link #isParallel()}) but the wrapped spliterator may choose to * not support splitting. When the returned stream is closed, the close * handlers for both the returned and this stream are invoked. * * @apiNote * While {@code dropWhile()} is generally a cheap operation on sequential * stream pipelines, it can be quite expensive on ordered parallel * pipelines, since the operation is constrained to return not just any * valid prefix, but the longest prefix of 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 dropWhile()} 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 dropWhile()} in parallel pipelines, switching to * sequential execution with {@link #sequential()} may improve performance. * * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * predicate to apply to elements to determine the longest * prefix of elements. * @return the new stream * @since 9 */ default IntStream dropWhile(IntPredicate predicate) { Objects.requireNonNull(predicate); // Reuses the unordered spliterator, which, when encounter is present, // is safe to use as long as it configured not to split return StreamSupport .intStream(new WhileOps.UnorderedWhileSpliterator.OfInt.Dropping(spliterator(), true, predicate), isParallel()) .onClose(this::close); } /** * Performs an action for each element of this stream. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * <p>For parallel stream pipelines, this operation does <em>not</em> * 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 <a href="package-summary.html#NonInterference"> * non-interfering</a> 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. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @param action a <a href="package-summary.html#NonInterference"> * non-interfering</a> action to perform on the elements * @see #forEach(IntConsumer) */ void forEachOrdered(IntConsumer action); /** * Returns an array containing the elements of this stream. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @return an array containing the elements of this stream */ int[] toArray(); /** * Performs a <a href="package-summary.html#Reduction">reduction</a> on the * elements of this stream, using the provided identity value and an * <a href="package-summary.html#Associativity">associative</a> * accumulation function, and returns the reduced value. This is equivalent * to: * <pre>{@code * int result = identity; * for (int element : this stream) * result = accumulator.applyAsInt(result, element) * return result; * }</pre> * * but is not constrained to execute sequentially. * * <p>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 * <a href="package-summary.html#Associativity">associative</a> function. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @apiNote Sum, min, max, and average are all special cases of reduction. * Summing a stream of numbers can be expressed as: * * <pre>{@code * int sum = integers.reduce(0, (a, b) -> a+b); * }</pre> * * or more compactly: * * <pre>{@code * int sum = integers.reduce(0, Integer::sum); * }</pre> * * <p>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 <a href="package-summary.html#Associativity">associative</a>, * <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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 <a href="package-summary.html#Reduction">reduction</a> on the * elements of this stream, using an * <a href="package-summary.html#Associativity">associative</a> accumulation * function, and returns an {@code OptionalInt} describing the reduced value, * if any. This is equivalent to: * <pre>{@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(); * }</pre> * * but is not constrained to execute sequentially. * * <p>The {@code accumulator} function must be an * <a href="package-summary.html#Associativity">associative</a> function. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @param op an <a href="package-summary.html#Associativity">associative</a>, * <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * function for combining two values * @return the result of the reduction * @see #reduce(int, IntBinaryOperator) */ OptionalInt reduce(IntBinaryOperator op); /** * Performs a <a href="package-summary.html#MutableReduction">mutable * reduction</a> 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: * <pre>{@code * R result = supplier.get(); * for (int element : this stream) * accumulator.accept(result, element); * return result; * }</pre> * * <p>Like {@link #reduce(int, IntBinaryOperator)}, {@code collect} operations * can be parallelized without requiring additional synchronization. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @param <R> the type of the mutable result container * @param supplier a function that creates a new mutable result container. * For a parallel execution, this function may be called * multiple times and must return a fresh value each time. * @param accumulator an <a href="package-summary.html#Associativity">associative</a>, * <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * function that must fold an element into a result * container. * @param combiner an <a href="package-summary.html#Associativity">associative</a>, * <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * function that accepts two partial result containers * and merges them, which must be compatible with the * accumulator function. The combiner function must fold * the elements from the second result container into the * first result container. * @return the result of the reduction * @see Stream#collect(Supplier, BiConsumer, BiConsumer) */ <R> R collect(Supplier<R> supplier, ObjIntConsumer<R> accumulator, BiConsumer<R, R> combiner); /** * Returns the sum of elements in this stream. This is a special case * of a <a href="package-summary.html#Reduction">reduction</a> * and is equivalent to: * <pre>{@code * return reduce(0, Integer::sum); * }</pre> * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @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 <a href="package-summary.html#Reduction">reduction</a> * and is equivalent to: * <pre>{@code * return reduce(Integer::min); * }</pre> * * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. * * @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 <a href="package-summary.html#Reduction">reduction</a> * and is equivalent to: * <pre>{@code * return reduce(Integer::max); * }</pre> * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @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 <a href="package-summary.html#Reduction">reduction</a> and is * equivalent to: * <pre>{@code * return mapToLong(e -> 1L).sum(); * }</pre> * * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. * * @apiNote * An implementation may choose to not execute the stream pipeline (either * sequentially or in parallel) if it is capable of computing the count * directly from the stream source. In such cases no source elements will * be traversed and no intermediate operations will be evaluated. * Behavioral parameters with side-effects, which are strongly discouraged * except for harmless cases such as debugging, may be affected. For * example, consider the following stream: * <pre>{@code * IntStream s = IntStream.of(1, 2, 3, 4); * long count = s.peek(System.out::println).count(); * }</pre> * The number of elements covered by the stream source is known and the * intermediate operation, {@code peek}, does not inject into or remove * elements from the stream (as may be the case for {@code flatMap} or * {@code filter} operations). Thus the count is 4 and there is no need to * execute the pipeline and, as a side-effect, print out the elements. * * @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 * <a href="package-summary.html#Reduction">reduction</a>. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @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 <a href="package-summary.html#Reduction">reduction</a>. * * <p>This is a <a href="package-summary.html#StreamOps">terminal * operation</a>. * * @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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * terminal operation</a>. * * @apiNote * This method evaluates the <em>existential quantification</em> of the * predicate over the elements of the stream (for some x P(x)). * * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * terminal operation</a>. * * @apiNote * This method evaluates the <em>universal quantification</em> 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 <em>vacuously * satisfied</em> and is always {@code true} (regardless of P(x)). * * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * terminal operation</a>. * * @apiNote * This method evaluates the <em>universal quantification</em> 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 <a href="package-summary.html#NonInterference">non-interfering</a>, * <a href="package-summary.html#Statelessness">stateless</a> * 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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * terminal operation</a>. * * @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. * * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting * terminal operation</a>. * * <p>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}. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @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}. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @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}. * * <p>This is an <a href="package-summary.html#StreamOps">intermediate * operation</a>. * * @return a {@code Stream} consistent of the elements of this stream, * each boxed to an {@code Integer} */ Stream<Integer> 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. * * <p>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}. * * <p>The action of applying {@code f} for one element * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a> * the action of applying {@code f} for subsequent elements. For any given * element the action may be performed in whatever thread the library * chooses. * * @param seed the initial element * @param f a function to be applied 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); Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE, Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) { int prev; boolean started; @Override public boolean tryAdvance(IntConsumer action) { Objects.requireNonNull(action); int t; if (started) t = f.applyAsInt(prev); else { t = seed; started = true; } action.accept(prev = t); return true; } }; return StreamSupport.intStream(spliterator, false); } /** * Returns a sequential ordered {@code IntStream} produced by iterative * application of the given {@code next} function to an initial element, * conditioned on satisfying the given {@code hasNext} predicate. The * stream terminates as soon as the {@code hasNext} predicate returns false. * * <p>{@code IntStream.iterate} should produce the same sequence of elements as * produced by the corresponding for-loop: * <pre>{@code * for (int index=seed; hasNext.test(index); index = next.applyAsInt(index)) { * ... * } * }</pre> * * <p>The resulting sequence may be empty if the {@code hasNext} predicate * does not hold on the seed value. Otherwise the first element will be the * supplied {@code seed} value, the next element (if present) will be the * result of applying the {@code next} function to the {@code seed} value, * and so on iteratively until the {@code hasNext} predicate indicates that * the stream should terminate. * * <p>The action of applying the {@code hasNext} predicate to an element * <a href="../concurrent/package-summary.html#MemoryVisibility"><i>happens-before</i></a> * the action of applying the {@code next} function to that element. The * action of applying the {@code next} function for one element * <i>happens-before</i> the action of applying the {@code hasNext} * predicate for subsequent elements. For any given element an action may * be performed in whatever thread the library chooses. * * @param seed the initial element * @param hasNext a predicate to apply to elements to determine when the * stream must terminate. * @param next a function to be applied to the previous element to produce * a new element * @return a new sequential {@code IntStream} * @since 9 */ public static IntStream iterate(int seed, IntPredicate hasNext, IntUnaryOperator next) { Objects.requireNonNull(next); Objects.requireNonNull(hasNext); Spliterator.OfInt spliterator = new Spliterators.AbstractIntSpliterator(Long.MAX_VALUE, Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) { int prev; boolean started, finished; @Override public boolean tryAdvance(IntConsumer action) { Objects.requireNonNull(action); if (finished) return false; int t; if (started) t = next.applyAsInt(prev); else { t = seed; started = true; } if (!hasNext.test(t)) { finished = true; return false; } action.accept(prev = t); return true; } @Override public void forEachRemaining(IntConsumer action) { Objects.requireNonNull(action); if (finished) return; finished = true; int t = started ? next.applyAsInt(prev) : seed; while (hasNext.test(t)) { action.accept(t); t = next.applyAsInt(t); } } }; return StreamSupport.intStream(spliterator, 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 * <p>An equivalent sequence of increasing values can be produced * sequentially using a {@code for} loop as follows: * <pre>{@code * for (int i = startInclusive; i < endExclusive ; i++) { ... } * }</pre> * * @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 * <p>An equivalent sequence of increasing values can be produced * sequentially using a {@code for} loop as follows: * <pre>{@code * for (int i = startInclusive; i <= endInclusive ; i++) { ... } * }</pre> * * @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. * * <p>This method operates on the two input streams and binds each stream * to its source. As a result subsequent modifications to an input stream * source may not be reflected in the concatenated stream result. * * @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 StackOverflowError}. * * @apiNote * To preserve optimization opportunities this method binds each stream to * its source and accepts only two streams as parameters. For example, the * exact size of the concatenated stream source can be computed if the exact * size of each input stream source is known. * To concatenate more streams without binding, or without nested calls to * this method, try creating a stream of streams and flat-mapping with the * identity function, for example: * <pre>{@code * IntStream concat = Stream.of(s1, s2, s3, s4).flatMapToInt(s -> s); * }</pre> * * @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}. * * <p>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: * <pre>{@code * accept(t) * return this; * }</pre> * * @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(); } }