compact1, compact2, compact3
java.util.concurrent
Class RecursiveTask<V>
- 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; } 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 and Description RecursiveTask()
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Method Summary
All Methods Instance Methods Abstract Methods Concrete Methods Modifier and Type Method and Description protected abstract Vcompute()The main computation performed by this task.protected booleanexec()Implements execution conventions for RecursiveTask.VgetRawResult()Returns the result that would be returned byForkJoinTask.join(), even if this task completed abnormally, ornullif this task is not known to have been completed.protected voidsetRawResult(V value)Forces the given value to be returned as a result.-
Methods inherited from 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, pollTask, quietlyComplete, quietlyInvoke, quietlyJoin, reinitialize, setForkJoinTaskTag, tryUnfork
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Method Detail
compute
protected abstract V compute()
The main computation performed by this task.- Returns:
- the result of the computation
getRawResult
public final V getRawResult()
Description copied from class:ForkJoinTaskReturns the result that would be returned byForkJoinTask.join(), even if this task completed abnormally, ornullif 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:
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getRawResultin classForkJoinTask<V> - Returns:
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the result, or
nullif not completed
setRawResult
protected final void setRawResult(V value)
Description copied from class:ForkJoinTaskForces 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:
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setRawResultin classForkJoinTask<V> - Parameters:
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value- the value
exec
protected final boolean exec()
Implements execution conventions for RecursiveTask.- Specified by:
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execin classForkJoinTask<V> - Returns:
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trueif this task is known to have completed normally
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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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