| /* |
| * Copyright (c) 2013, 2020, 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.LongSummaryStatistics; |
| import java.util.Objects; |
| import java.util.OptionalDouble; |
| import java.util.OptionalLong; |
| 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.LongBinaryOperator; |
| import java.util.function.LongConsumer; |
| import java.util.function.LongFunction; |
| import java.util.function.LongPredicate; |
| import java.util.function.LongSupplier; |
| import java.util.function.LongToDoubleFunction; |
| import java.util.function.LongToIntFunction; |
| import java.util.function.LongUnaryOperator; |
| import java.util.function.ObjLongConsumer; |
| import java.util.function.Supplier; |
| |
| /** |
| * A sequence of primitive long-valued elements supporting sequential and parallel |
| * aggregate operations. This is the {@code long} primitive specialization of |
| * {@link Stream}. |
| * |
| * <p>The following example illustrates an aggregate operation using |
| * {@link Stream} and {@link LongStream}, computing the sum of the weights of the |
| * red widgets: |
| * |
| * <pre>{@code |
| * long sum = widgets.stream() |
| * .filter(w -> w.getColor() == RED) |
| * .mapToLong(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 LongStream extends BaseStream<Long, LongStream> { |
| |
| /** |
| * 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 |
| */ |
| LongStream filter(LongPredicate 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 |
| */ |
| LongStream map(LongUnaryOperator 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(LongFunction<? extends U> mapper); |
| |
| /** |
| * Returns an {@code IntStream} 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 mapToInt(LongToIntFunction 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(LongToDoubleFunction 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 a |
| * {@code LongStream} of new values |
| * @return the new stream |
| * @see Stream#flatMap(Function) |
| */ |
| LongStream flatMap(LongFunction<? extends LongStream> mapper); |
| |
| /** |
| * Returns a stream consisting of the results of replacing each element of |
| * this stream with multiple elements, specifically zero or more elements. |
| * Replacement is performed by applying the provided mapping function to each |
| * element in conjunction with a {@linkplain LongConsumer consumer} argument |
| * that accepts replacement elements. The mapping function calls the consumer |
| * zero or more times to provide the replacement elements. |
| * |
| * <p>This is an <a href="package-summary.html#StreamOps">intermediate |
| * operation</a>. |
| * |
| * <p>If the {@linkplain LongConsumer consumer} argument is used outside the scope of |
| * its application to the mapping function, the results are undefined. |
| * |
| * @implSpec |
| * The default implementation invokes {@link #flatMap flatMap} on this stream, |
| * passing a function that behaves as follows. First, it calls the mapper function |
| * with a {@code LongConsumer} that accumulates replacement elements into a newly created |
| * internal buffer. When the mapper function returns, it creates a {@code LongStream} from the |
| * internal buffer. Finally, it returns this stream to {@code flatMap}. |
| * |
| * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, |
| * <a href="package-summary.html#Statelessness">stateless</a> |
| * function that generates replacement elements |
| * @return the new stream |
| * @see Stream#mapMulti Stream.mapMulti |
| * @since 16 |
| */ |
| default LongStream mapMulti(LongMapMultiConsumer mapper) { |
| Objects.requireNonNull(mapper); |
| return flatMap(e -> { |
| SpinedBuffer.OfLong buffer = new SpinedBuffer.OfLong(); |
| mapper.accept(e, buffer); |
| return StreamSupport.longStream(buffer.spliterator(), false); |
| }); |
| } |
| |
| /** |
| * 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 |
| */ |
| LongStream 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 |
| */ |
| LongStream 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 |
| * LongStream.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 |
| */ |
| LongStream peek(LongConsumer 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(LongSupplier)}) 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 |
| */ |
| LongStream 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(LongSupplier)}) 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 |
| */ |
| LongStream 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(LongSupplier)}) 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 LongStream takeWhile(LongPredicate 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.longStream( |
| new WhileOps.UnorderedWhileSpliterator.OfLong.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(LongSupplier)}) 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 LongStream dropWhile(LongPredicate 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.longStream( |
| new WhileOps.UnorderedWhileSpliterator.OfLong.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(LongConsumer action); |
| |
| /** |
| * Performs an action for each element of this stream, guaranteeing that |
| * each element is processed in encounter order for streams that have a |
| * defined encounter order. |
| * |
| * <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(LongConsumer) |
| */ |
| void forEachOrdered(LongConsumer 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 |
| */ |
| long[] 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 |
| * long result = identity; |
| * for (long element : this stream) |
| * result = accumulator.applyAsLong(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 |
| * long sum = integers.reduce(0, (a, b) -> a+b); |
| * }</pre> |
| * |
| * or more compactly: |
| * |
| * <pre>{@code |
| * long sum = integers.reduce(0, Long::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() |
| */ |
| long reduce(long identity, LongBinaryOperator 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 OptionalLong} describing the reduced value, |
| * if any. This is equivalent to: |
| * <pre>{@code |
| * boolean foundAny = false; |
| * long result = null; |
| * for (long element : this stream) { |
| * if (!foundAny) { |
| * foundAny = true; |
| * result = element; |
| * } |
| * else |
| * result = accumulator.applyAsLong(result, element); |
| * } |
| * return foundAny ? OptionalLong.of(result) : OptionalLong.empty(); |
| * }</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(long, LongBinaryOperator) |
| */ |
| OptionalLong reduce(LongBinaryOperator 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 (long element : this stream) |
| * accumulator.accept(result, element); |
| * return result; |
| * }</pre> |
| * |
| * <p>Like {@link #reduce(long, LongBinaryOperator)}, {@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, |
| ObjLongConsumer<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, Long::sum); |
| * }</pre> |
| * |
| * <p>This is a <a href="package-summary.html#StreamOps">terminal |
| * operation</a>. |
| * |
| * @return the sum of elements in this stream |
| */ |
| long sum(); |
| |
| /** |
| * Returns an {@code OptionalLong} 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(Long::min); |
| * }</pre> |
| * |
| * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. |
| * |
| * @return an {@code OptionalLong} containing the minimum element of this |
| * stream, or an empty {@code OptionalLong} if the stream is empty |
| */ |
| OptionalLong min(); |
| |
| /** |
| * Returns an {@code OptionalLong} 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(Long::max); |
| * }</pre> |
| * |
| * <p>This is a <a href="package-summary.html#StreamOps">terminal |
| * operation</a>. |
| * |
| * @return an {@code OptionalLong} containing the maximum element of this |
| * stream, or an empty {@code OptionalLong} if the stream is empty |
| */ |
| OptionalLong 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 map(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 |
| * LongStream s = LongStream.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 a {@code LongSummaryStatistics} 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 a {@code LongSummaryStatistics} describing various summary data |
| * about the elements of this stream |
| */ |
| LongSummaryStatistics 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(LongPredicate predicate); |
| |
| /** |
| * Returns whether all elements of this stream match the provided predicate. |
| * May not evaluate the predicate on all elements if not necessary for |
| * determining the result. If the stream is empty then {@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(LongPredicate predicate); |
| |
| /** |
| * Returns whether no elements of this stream match the provided predicate. |
| * May not evaluate the predicate on all elements if not necessary for |
| * determining the result. If the stream is empty then {@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(LongPredicate predicate); |
| |
| /** |
| * Returns an {@link OptionalLong} describing the first element of this |
| * stream, or an empty {@code OptionalLong} 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 OptionalLong} describing the first element of this |
| * stream, or an empty {@code OptionalLong} if the stream is empty |
| */ |
| OptionalLong findFirst(); |
| |
| /** |
| * Returns an {@link OptionalLong} describing some element of the stream, or |
| * an empty {@code OptionalLong} 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 OptionalLong} describing some element of this stream, |
| * or an empty {@code OptionalLong} if the stream is empty |
| * @see #findFirst() |
| */ |
| OptionalLong findAny(); |
| |
| /** |
| * 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 a {@code Long}. |
| * |
| * <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 {@code Long} |
| */ |
| Stream<Long> boxed(); |
| |
| @Override |
| LongStream sequential(); |
| |
| @Override |
| LongStream parallel(); |
| |
| @Override |
| PrimitiveIterator.OfLong iterator(); |
| |
| @Override |
| Spliterator.OfLong spliterator(); |
| |
| // Static factories |
| |
| /** |
| * Returns a builder for a {@code LongStream}. |
| * |
| * @return a stream builder |
| */ |
| public static Builder builder() { |
| return new Streams.LongStreamBuilderImpl(); |
| } |
| |
| /** |
| * Returns an empty sequential {@code LongStream}. |
| * |
| * @return an empty sequential stream |
| */ |
| public static LongStream empty() { |
| return StreamSupport.longStream(Spliterators.emptyLongSpliterator(), false); |
| } |
| |
| /** |
| * Returns a sequential {@code LongStream} containing a single element. |
| * |
| * @param t the single element |
| * @return a singleton sequential stream |
| */ |
| public static LongStream of(long t) { |
| return StreamSupport.longStream(new Streams.LongStreamBuilderImpl(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 LongStream of(long... values) { |
| return Arrays.stream(values); |
| } |
| |
| /** |
| * Returns an infinite sequential ordered {@code LongStream} 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 LongStream} 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 LongStream} |
| */ |
| public static LongStream iterate(final long seed, final LongUnaryOperator f) { |
| Objects.requireNonNull(f); |
| Spliterator.OfLong spliterator = new Spliterators.AbstractLongSpliterator(Long.MAX_VALUE, |
| Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) { |
| long prev; |
| boolean started; |
| |
| @Override |
| public boolean tryAdvance(LongConsumer action) { |
| Objects.requireNonNull(action); |
| long t; |
| if (started) |
| t = f.applyAsLong(prev); |
| else { |
| t = seed; |
| started = true; |
| } |
| action.accept(prev = t); |
| return true; |
| } |
| }; |
| return StreamSupport.longStream(spliterator, false); |
| } |
| |
| /** |
| * Returns a sequential ordered {@code LongStream} 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 LongStream.iterate} should produce the same sequence of elements as |
| * produced by the corresponding for-loop: |
| * <pre>{@code |
| * for (long index=seed; hasNext.test(index); index = next.applyAsLong(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 LongStream} |
| * @since 9 |
| */ |
| public static LongStream iterate(long seed, LongPredicate hasNext, LongUnaryOperator next) { |
| Objects.requireNonNull(next); |
| Objects.requireNonNull(hasNext); |
| Spliterator.OfLong spliterator = new Spliterators.AbstractLongSpliterator(Long.MAX_VALUE, |
| Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL) { |
| long prev; |
| boolean started, finished; |
| |
| @Override |
| public boolean tryAdvance(LongConsumer action) { |
| Objects.requireNonNull(action); |
| if (finished) |
| return false; |
| long t; |
| if (started) |
| t = next.applyAsLong(prev); |
| else { |
| t = seed; |
| started = true; |
| } |
| if (!hasNext.test(t)) { |
| finished = true; |
| return false; |
| } |
| action.accept(prev = t); |
| return true; |
| } |
| |
| @Override |
| public void forEachRemaining(LongConsumer action) { |
| Objects.requireNonNull(action); |
| if (finished) |
| return; |
| finished = true; |
| long t = started ? next.applyAsLong(prev) : seed; |
| while (hasNext.test(t)) { |
| action.accept(t); |
| t = next.applyAsLong(t); |
| } |
| } |
| }; |
| return StreamSupport.longStream(spliterator, false); |
| } |
| |
| /** |
| * Returns an infinite sequential unordered stream where each element is |
| * generated by the provided {@code LongSupplier}. This is suitable for |
| * generating constant streams, streams of random elements, etc. |
| * |
| * @param s the {@code LongSupplier} for generated elements |
| * @return a new infinite sequential unordered {@code LongStream} |
| */ |
| public static LongStream generate(LongSupplier s) { |
| Objects.requireNonNull(s); |
| return StreamSupport.longStream( |
| new StreamSpliterators.InfiniteSupplyingSpliterator.OfLong(Long.MAX_VALUE, s), false); |
| } |
| |
| /** |
| * Returns a sequential ordered {@code LongStream} 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 (long i = startInclusive; i < endExclusive ; i++) { ... } |
| * }</pre> |
| * |
| * @param startInclusive the (inclusive) initial value |
| * @param endExclusive the exclusive upper bound |
| * @return a sequential {@code LongStream} for the range of {@code long} |
| * elements |
| */ |
| public static LongStream range(long startInclusive, final long endExclusive) { |
| if (startInclusive >= endExclusive) { |
| return empty(); |
| } else if (endExclusive - startInclusive < 0) { |
| // Size of range > Long.MAX_VALUE |
| // Split the range in two and concatenate |
| // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE) then |
| // the lower range, [Long.MIN_VALUE, 0) will be further split in two |
| long m = startInclusive + Long.divideUnsigned(endExclusive - startInclusive, 2) + 1; |
| return concat(range(startInclusive, m), range(m, endExclusive)); |
| } else { |
| return StreamSupport.longStream( |
| new Streams.RangeLongSpliterator(startInclusive, endExclusive, false), false); |
| } |
| } |
| |
| /** |
| * Returns a sequential ordered {@code LongStream} 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 (long i = startInclusive; i <= endInclusive ; i++) { ... } |
| * }</pre> |
| * |
| * @param startInclusive the (inclusive) initial value |
| * @param endInclusive the inclusive upper bound |
| * @return a sequential {@code LongStream} for the range of {@code long} |
| * elements |
| */ |
| public static LongStream rangeClosed(long startInclusive, final long endInclusive) { |
| if (startInclusive > endInclusive) { |
| return empty(); |
| } else if (endInclusive - startInclusive + 1 <= 0) { |
| // Size of range > Long.MAX_VALUE |
| // Split the range in two and concatenate |
| // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE] then |
| // the lower range, [Long.MIN_VALUE, 0), and upper range, |
| // [0, Long.MAX_VALUE], will both be further split in two |
| long m = startInclusive + Long.divideUnsigned(endInclusive - startInclusive, 2) + 1; |
| return concat(range(startInclusive, m), rangeClosed(m, endInclusive)); |
| } else { |
| return StreamSupport.longStream( |
| new Streams.RangeLongSpliterator(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 |
| * LongStream concat = Stream.of(s1, s2, s3, s4).flatMapToLong(s -> s); |
| * }</pre> |
| * |
| * @param a the first stream |
| * @param b the second stream |
| * @return the concatenation of the two input streams |
| */ |
| public static LongStream concat(LongStream a, LongStream b) { |
| Objects.requireNonNull(a); |
| Objects.requireNonNull(b); |
| |
| Spliterator.OfLong split = new Streams.ConcatSpliterator.OfLong( |
| a.spliterator(), b.spliterator()); |
| LongStream stream = StreamSupport.longStream(split, a.isParallel() || b.isParallel()); |
| return stream.onClose(Streams.composedClose(a, b)); |
| } |
| |
| /** |
| * A mutable builder for a {@code LongStream}. |
| * |
| * <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 |
| * 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 LongStream#builder() |
| * @since 1.8 |
| */ |
| public interface Builder extends LongConsumer { |
| |
| /** |
| * Adds an element to the stream being built. |
| * |
| * @throws IllegalStateException if the builder has already transitioned |
| * to the built state |
| */ |
| @Override |
| void accept(long 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(long 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 |
| */ |
| LongStream build(); |
| } |
| |
| /** |
| * Represents an operation that accepts a {@code long}-valued argument |
| * and a LongConsumer, and returns no result. This functional interface is |
| * used by {@link LongStream#mapMulti(LongStream.LongMapMultiConsumer) LongStream.mapMulti} |
| * to replace a long value with zero or more long values. |
| * |
| * <p>This is a <a href="../function/package-summary.html">functional interface</a> |
| * whose functional method is {@link #accept(long, LongConsumer)}. |
| * |
| * @see LongStream#mapMulti(LongStream.LongMapMultiConsumer) |
| * |
| * @since 16 |
| */ |
| @FunctionalInterface |
| interface LongMapMultiConsumer { |
| |
| /** |
| * Replaces the given {@code value} with zero or more values by feeding the mapped |
| * values to the {@code lc} consumer. |
| * |
| * @param value the long value coming from upstream |
| * @param lc a {@code LongConsumer} accepting the mapped values |
| */ |
| void accept(long value, LongConsumer lc); |
| } |
| } |
