| /* |
| * 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. |
| */ |
| |
| /* |
| * This file is available under and governed by the GNU General Public |
| * License version 2 only, as published by the Free Software Foundation. |
| * However, the following notice accompanied the original version of this |
| * file: |
| * |
| * Written by Doug Lea with assistance from members of JCP JSR-166 |
| * Expert Group and released to the public domain, as explained at |
| * http://creativecommons.org/publicdomain/zero/1.0/ |
| */ |
| |
| package java.util.concurrent; |
| |
| /** |
| * A recursive result-bearing {@link ForkJoinTask}. |
| * |
| * <p>For a classic example, here is a task computing Fibonacci numbers: |
| * |
| * <pre> {@code |
| * class Fibonacci extends RecursiveTask<Integer> { |
| * final int n; |
| * Fibonacci(int n) { this.n = n; } |
| * protected Integer compute() { |
| * if (n <= 1) |
| * return n; |
| * Fibonacci f1 = new Fibonacci(n - 1); |
| * f1.fork(); |
| * Fibonacci f2 = new Fibonacci(n - 2); |
| * return f2.compute() + f1.join(); |
| * } |
| * }}</pre> |
| * |
| * However, besides being a dumb way to compute Fibonacci functions |
| * (there is a simple fast linear algorithm that you'd use in |
| * practice), this is likely to perform poorly because the smallest |
| * subtasks are too small to be worthwhile splitting up. Instead, as |
| * is the case for nearly all fork/join applications, you'd pick some |
| * minimum granularity size (for example 10 here) for which you always |
| * sequentially solve rather than subdividing. |
| * |
| * @since 1.7 |
| * @author Doug Lea |
| */ |
| public abstract class RecursiveTask<V> extends ForkJoinTask<V> { |
| private static final long serialVersionUID = 5232453952276485270L; |
| |
| /** |
| * The result of the computation. |
| */ |
| V result; |
| |
| /** |
| * The main computation performed by this task. |
| * @return the result of the computation |
| */ |
| protected abstract V compute(); |
| |
| public final V getRawResult() { |
| return result; |
| } |
| |
| protected final void setRawResult(V value) { |
| result = value; |
| } |
| |
| /** |
| * Implements execution conventions for RecursiveTask. |
| */ |
| protected final boolean exec() { |
| result = compute(); |
| return true; |
| } |
| |
| } |