diff -r 000000000000 -r 212417b74b72 rt/emul/compact/src/main/java/java/util/concurrent/RecursiveTask.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/RecursiveTask.java Sat Mar 19 10:46:31 2016 +0100 @@ -0,0 +1,97 @@ +/* + * 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}. + * + *

For a classic example, here is a task computing Fibonacci numbers: + * + *

 {@code
+ * class Fibonacci extends RecursiveTask {
+ *   final int n;
+ *   Fibonacci(int n) { this.n = n; }
+ *   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();
+ *   }
+ * }}
+ * + * 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 extends ForkJoinTask { + private static final long serialVersionUID = 5232453952276485270L; + + /** + * The result of the computation. + */ + V result; + + /** + * The main computation performed by this task. + */ + 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; + } + +}