java.lang.Object
java.util.concurrent.ForkJoinTask<V>
java.util.concurrent.RecursiveTask<V>
 All Implemented Interfaces:
Serializable
,Future<V>
A recursive resultbearing
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. Since:
 1.7
 See Also:
 Serialized Form

Constructor Summary

Method Summary
Modifier and TypeMethodDescriptionprotected abstract V
compute()
The main computation performed by this task.protected boolean
exec()
Implements execution conventions for RecursiveTask.Returns the result that would be returned byForkJoinTask.join()
, even if this task completed abnormally, ornull
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.Methods declared in class java.util.concurrent.ForkJoinTask
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

Constructor Details

RecursiveTask
public RecursiveTask()Constructor for subclasses to call.


Method Details

compute
The main computation performed by this task. Returns:
 the result of the computation

getRawResult
Description copied from class:ForkJoinTask
Returns the result that would be returned byForkJoinTask.join()
, even if this task completed abnormally, ornull
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. Specified by:
getRawResult
in classForkJoinTask<V>
 Returns:
 the result, or
null
if not completed

setRawResult
Description copied from class:ForkJoinTask
Forces the given value to be returned as a result. This method is designed to support extensions, and should not in general be called otherwise. Specified by:
setRawResult
in classForkJoinTask<V>
 Parameters:
value
 the value

exec
protected final boolean exec()Implements execution conventions for RecursiveTask. Specified by:
exec
in classForkJoinTask<V>
 Returns:
true
if this task is known to have completed normally
