| /* |
| * 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 |
| * @hide |
| * @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; |
| } |
| |
| } |