/* * 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; } * 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. */ 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; }}
/*
* 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; }
* 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.
*/
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;
}
}