Serializable
, Future<V>
public abstract class RecursiveTask<V> extends ForkJoinTask<V>
ForkJoinTask
.
For a classic example, here is a task computing Fibonacci numbers:
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();
}
}
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.Constructor  Description 

RecursiveTask() 
Modifier and Type  Method  Description 

protected abstract V 
compute() 
The main computation performed by this task.

protected boolean 
exec() 
Implements execution conventions for RecursiveTask.

V 
getRawResult() 
Returns the result that would be returned by
ForkJoinTask.join() , even
if this task completed abnormally, or null if this task
is not known to have been completed. 
protected void 
setRawResult(V value) 
Forces the given value to be returned as a result.

adapt, adapt, adapt, cancel, compareAndSetForkJoinTaskTag, complete, completeExceptionally, fork, get, get, getException, getForkJoinTaskTag, getPool, getQueuedTaskCount, getSurplusQueuedTaskCount, helpQuiesce, inForkJoinPool, invoke, invokeAll, invokeAll, invokeAll, isCancelled, isCompletedAbnormally, isCompletedNormally, isDone, join, peekNextLocalTask, pollNextLocalTask, pollSubmission, pollTask, quietlyComplete, quietlyInvoke, quietlyJoin, reinitialize, setForkJoinTaskTag, tryUnfork
protected abstract V compute()
public final V getRawResult()
ForkJoinTask
ForkJoinTask.join()
, even
if this task completed abnormally, or null
if this task
is not known to have been completed. This method is designed
to aid debugging, as well as to support extensions. Its use in
any other context is discouraged.getRawResult
in class ForkJoinTask<V>
null
if not completedprotected final void setRawResult(V value)
ForkJoinTask
setRawResult
in class ForkJoinTask<V>
value
 the valueprotected final boolean exec()
exec
in class ForkJoinTask<V>
true
if this task is known to have completed normally