1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/rt/emul/compact/src/main/java/java/util/concurrent/RecursiveTask.java	Sat Mar 19 10:46:31 2016 +0100
     1.3 @@ -0,0 +1,97 @@
     1.4 +/*
     1.5 + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
     1.6 + *
     1.7 + * This code is free software; you can redistribute it and/or modify it
     1.8 + * under the terms of the GNU General Public License version 2 only, as
     1.9 + * published by the Free Software Foundation.  Oracle designates this
    1.10 + * particular file as subject to the "Classpath" exception as provided
    1.11 + * by Oracle in the LICENSE file that accompanied this code.
    1.12 + *
    1.13 + * This code is distributed in the hope that it will be useful, but WITHOUT
    1.14 + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
    1.15 + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    1.16 + * version 2 for more details (a copy is included in the LICENSE file that
    1.17 + * accompanied this code).
    1.18 + *
    1.19 + * You should have received a copy of the GNU General Public License version
    1.20 + * 2 along with this work; if not, write to the Free Software Foundation,
    1.21 + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
    1.22 + *
    1.23 + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
    1.24 + * or visit www.oracle.com if you need additional information or have any
    1.25 + * questions.
    1.26 + */
    1.27 +
    1.28 +/*
    1.29 + * This file is available under and governed by the GNU General Public
    1.30 + * License version 2 only, as published by the Free Software Foundation.
    1.31 + * However, the following notice accompanied the original version of this
    1.32 + * file:
    1.33 + *
    1.34 + * Written by Doug Lea with assistance from members of JCP JSR-166
    1.35 + * Expert Group and released to the public domain, as explained at
    1.36 + * http://creativecommons.org/publicdomain/zero/1.0/
    1.37 + */
    1.38 +
    1.39 +package java.util.concurrent;
    1.40 +
    1.41 +/**
    1.42 + * A recursive result-bearing {@link ForkJoinTask}.
    1.43 + *
    1.44 + * <p>For a classic example, here is a task computing Fibonacci numbers:
    1.45 + *
    1.46 + *  <pre> {@code
    1.47 + * class Fibonacci extends RecursiveTask<Integer> {
    1.48 + *   final int n;
    1.49 + *   Fibonacci(int n) { this.n = n; }
    1.50 + *   Integer compute() {
    1.51 + *     if (n <= 1)
    1.52 + *        return n;
    1.53 + *     Fibonacci f1 = new Fibonacci(n - 1);
    1.54 + *     f1.fork();
    1.55 + *     Fibonacci f2 = new Fibonacci(n - 2);
    1.56 + *     return f2.compute() + f1.join();
    1.57 + *   }
    1.58 + * }}</pre>
    1.59 + *
    1.60 + * However, besides being a dumb way to compute Fibonacci functions
    1.61 + * (there is a simple fast linear algorithm that you'd use in
    1.62 + * practice), this is likely to perform poorly because the smallest
    1.63 + * subtasks are too small to be worthwhile splitting up. Instead, as
    1.64 + * is the case for nearly all fork/join applications, you'd pick some
    1.65 + * minimum granularity size (for example 10 here) for which you always
    1.66 + * sequentially solve rather than subdividing.
    1.67 + *
    1.68 + * @since 1.7
    1.69 + * @author Doug Lea
    1.70 + */
    1.71 +public abstract class RecursiveTask<V> extends ForkJoinTask<V> {
    1.72 +    private static final long serialVersionUID = 5232453952276485270L;
    1.73 +
    1.74 +    /**
    1.75 +     * The result of the computation.
    1.76 +     */
    1.77 +    V result;
    1.78 +
    1.79 +    /**
    1.80 +     * The main computation performed by this task.
    1.81 +     */
    1.82 +    protected abstract V compute();
    1.83 +
    1.84 +    public final V getRawResult() {
    1.85 +        return result;
    1.86 +    }
    1.87 +
    1.88 +    protected final void setRawResult(V value) {
    1.89 +        result = value;
    1.90 +    }
    1.91 +
    1.92 +    /**
    1.93 +     * Implements execution conventions for RecursiveTask.
    1.94 +     */
    1.95 +    protected final boolean exec() {
    1.96 +        result = compute();
    1.97 +        return true;
    1.98 +    }
    1.99 +
   1.100 +}