--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/util/concurrent/RecursiveTask.java Mon Nov 02 17:25:38 2009 -0800
@@ -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. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.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/licenses/publicdomain
+ */
+
+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;
+ }
+
+}