- java.lang.Object
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- java.util.concurrent.ForkJoinTask<V>
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- java.util.concurrent.RecursiveTask<V>
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- All Implemented Interfaces:
Serializable,Future<V>
public abstract class RecursiveTask<V> extends ForkJoinTask<V>
A recursive result-bearingForkJoinTask.For a classic example, here is a task computing Fibonacci numbers:
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.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(); } }- Since:
- 1.7
- See Also:
- Serialized Form
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Constructor Summary
Constructors Constructor Description RecursiveTask()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method Description protected abstract Vcompute()The main computation performed by this task.protected booleanexec()Implements execution conventions for RecursiveTask.-
Methods declared in class java.util.concurrent.ForkJoinTask
adapt, adapt, adapt, cancel, compareAndSetForkJoinTaskTag, complete, completeExceptionally, fork, get, get, getException, getForkJoinTaskTag, getPool, getQueuedTaskCount, getRawResult, getSurplusQueuedTaskCount, helpQuiesce, inForkJoinPool, invoke, invokeAll, invokeAll, invokeAll, isCompletedAbnormally, isCompletedNormally, join, peekNextLocalTask, pollNextLocalTask, pollSubmission, pollTask, quietlyComplete, quietlyInvoke, quietlyJoin, reinitialize, setForkJoinTaskTag, setRawResult, tryUnfork
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Methods declared in class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods declared in interface java.util.concurrent.Future
isCancelled, isDone
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Method Detail
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compute
protected abstract V compute()
The main computation performed by this task.- Returns:
- the result of the computation
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exec
protected final boolean exec()
Implements execution conventions for RecursiveTask.- Specified by:
execin classForkJoinTask<V>- Returns:
trueif this task is known to have completed normally
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