/*

 * 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

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 */

/*

 * 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;

    }

}