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root/jsr166/jsr166/src/jsr166y/ForkJoinTask.java

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.29 by jsr166, Sun Aug 2 17:19:24 2009 UTC vs.
Revision 1.34 by dl, Tue Aug 4 11:44:33 2009 UTC

#	Line 12 | Line 12 | import java.io.Serializable;
12		import java.util.Collection;
13		import java.util.Collections;
14		import java.util.List;
15	+	import java.util.RandomAccess;
16		import java.util.Map;
17		import java.util.WeakHashMap;
18
#	Line 54 | Line 55 | import java.util.WeakHashMap;
55		* restriction is in part enforced by not permitting checked
56		* exceptions such as {@code IOExceptions} to be thrown. However,
57		* computations may still encounter unchecked exceptions, that are
58	<	* rethrown to callers attempting join them. These exceptions may
58	>	* rethrown to callers attempting to join them. These exceptions may
59		* additionally include RejectedExecutionExceptions stemming from
60		* internal resource exhaustion such as failure to allocate internal
61		* task queues.
#	Line 85 | Line 86 | import java.util.WeakHashMap;
86		* established in a constructor, and then defines a {@code compute}
87		* method that somehow uses the control methods supplied by this base
88		* class. While these methods have {@code public} access (to allow
89	<	* instances of different task subclasses to call each others
89	>	* instances of different task subclasses to call each other's
90		* methods), some of them may only be called from within other
91		* ForkJoinTasks (as may be determined using method {@link
92		* #inForkJoinPool}).  Attempts to invoke them in other contexts
93		* result in exceptions or errors, possibly including
94		* ClassCastException.
95		*
96	<	* <p>Most base support methods are {@code final} because their
97	<	* implementations are intrinsically tied to the underlying
98	<	* lightweight task scheduling framework, and so cannot be overridden.
99	<	* Developers creating new basic styles of fork/join processing should
100	<	* minimally implement {@code protected} methods
101	<	* {@link #exec}, {@link #setRawResult}, and
102	<	* {@link #getRawResult}, while also introducing an abstract
103	<	* computational method that can be implemented in its subclasses,
104	<	* possibly relying on other {@code protected} methods provided
104	<	* by this class.
96	>	* <p>Most base support methods are {@code final}, to prevent
97	>	* overriding of implementations that are intrinsically tied to the
98	>	* underlying lightweight task scheduling framework.  Developers
99	>	* creating new basic styles of fork/join processing should minimally
100	>	* implement {@code protected} methods {@link #exec}, {@link
101	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
102	>	* an abstract computational method that can be implemented in its
103	>	* subclasses, possibly relying on other {@code protected} methods
104	>	* provided by this class.
105		*
106		* <p>ForkJoinTasks should perform relatively small amounts of
107	<	* computations, otherwise splitting into smaller tasks. As a very
108	<	* rough rule of thumb, a task should perform more than 100 and less
109	<	* than 10000 basic computational steps. If tasks are too big, then
110	<	* parallelism cannot improve throughput. If too small, then memory
111	<	* and internal task maintenance overhead may overwhelm processing.
107	>	* computation. Large tasks should be split into smaller subtasks,
108	>	* usually via recursive decomposition. As a very rough rule of thumb,
109	>	* a task should perform more than 100 and less than 10000 basic
110	>	* computational steps. If tasks are too big, then parallelism cannot
111	>	* improve throughput. If too small, then memory and internal task
112	>	* maintenance overhead may overwhelm processing.
113		*
114		* <p>This class provides {@code adapt} methods for {@link
115		* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
116		* may be of use when mixing execution of ForkJoinTasks with other
117		* kinds of tasks. When all tasks are of this form, consider using a
118	<	* pool in {@link ForkJoinPool#setAsyncMode}.
118	>	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
119		*
120	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
121	<	* to be used in extensions such as remote execution frameworks. It is
122	<	* in general sensible to serialize tasks only before or after, but
123	<	* not during execution. Serialization is not relied on during
123	<	* execution itself.
120	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
121	>	* used in extensions such as remote execution frameworks. It is
122	>	* sensible to serialize tasks only before or after, but not during,
123	>	* execution. Serialization is not relied on during execution itself.
124		*
125		* @since 1.7
126		* @author Doug Lea
#	Line 382 | Line 382 | public abstract class ForkJoinTask<V> im
382		*/
383		private V reportFutureResult()
384		throws ExecutionException, InterruptedException {
385	+	if (Thread.interrupted())
386	+	throw new InterruptedException();
387		int s = status & COMPLETION_MASK;
388		if (s < NORMAL) {
389		Throwable ex;
#	Line 389 | Line 391 | public abstract class ForkJoinTask<V> im
391		throw new CancellationException();
392		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
393		throw new ExecutionException(ex);
392	–	if (Thread.interrupted())
393	–	throw new InterruptedException();
394		}
395		return getRawResult();
396		}
#	Line 401 | Line 401 | public abstract class ForkJoinTask<V> im
401		*/
402		private V reportTimedFutureResult()
403		throws InterruptedException, ExecutionException, TimeoutException {
404	+	if (Thread.interrupted())
405	+	throw new InterruptedException();
406		Throwable ex;
407		int s = status & COMPLETION_MASK;
408		if (s == NORMAL)
#	Line 409 | Line 411 | public abstract class ForkJoinTask<V> im
411		throw new CancellationException();
412		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
413		throw new ExecutionException(ex);
412	–	if (Thread.interrupted())
413	–	throw new InterruptedException();
414		throw new TimeoutException();
415		}
416
#	Line 496 | Line 496 | public abstract class ForkJoinTask<V> im
496		/**
497		* Arranges to asynchronously execute this task.  While it is not
498		* necessarily enforced, it is a usage error to fork a task more
499	<	* than once unless it has completed and been reinitialized.  This
500	<	* method may be invoked only from within ForkJoinTask
501	<	* computations (as may be determined using method {@link
502	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
503	<	* in exceptions or errors, possibly including ClassCastException.
499	>	* than once unless it has completed and been reinitialized.
500	>	*
501	>	* <p>This method may be invoked only from within {@code
502	>	* ForkJoinTask} computations (as may be determined using method
503	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
504	>	* result in exceptions or errors, possibly including {@code
505	>	* ClassCastException}.
506		*
507	<	* @return {@code this}, to simplify usage.
507	>	* @return {@code this}, to simplify usage
508		*/
509		public final ForkJoinTask<V> fork() {
510		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 512 | Line 514 | public abstract class ForkJoinTask<V> im
514
515		/**
516		* Returns the result of the computation when it is ready.
517	<	* This method differs from {@code get} in that abnormal
518	<	* completion results in RuntimeExceptions or Errors, not
519	<	* ExecutionExceptions.
517	>	* This method differs from {@link #get()} in that
518	>	* abnormal completion results in {@code RuntimeException} or
519	>	* {@code Error}, not {@code ExecutionException}.
520		*
521		* @return the computed result
522		*/
#	Line 527 | Line 529 | public abstract class ForkJoinTask<V> im
529
530		/**
531		* Commences performing this task, awaits its completion if
532	<	* necessary, and return its result.
532	>	* necessary, and return its result, or throws an (unchecked)
533	>	* exception if the underlying computation did so.
534		*
532	–	* @throws Throwable (a RuntimeException, Error, or unchecked
533	–	* exception) if the underlying computation did so
535		* @return the computed result
536		*/
537		public final V invoke() {
#	Line 542 | Line 543 | public abstract class ForkJoinTask<V> im
543
544		/**
545		* Forks the given tasks, returning when {@code isDone} holds for
546	<	* each task or an exception is encountered. This method may be
547	<	* invoked only from within ForkJoinTask computations (as may be
548	<	* determined using method {@link #inForkJoinPool}). Attempts to
549	<	* invoke in other contexts result in exceptions or errors,
550	<	* possibly including ClassCastException.
546	>	* each task or an (unchecked) exception is encountered, in which
547	>	* case the exception is rethrown.  If more than one task
548	>	* encounters an exception, then this method throws any one of
549	>	* these exceptions.  The individual status of each task may be
550	>	* checked using {@link #getException()} and related methods.
551	>	*
552	>	* <p>This method may be invoked only from within {@code
553	>	* ForkJoinTask} computations (as may be determined using method
554	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
555	>	* result in exceptions or errors, possibly including {@code
556	>	* ClassCastException}.
557		*
558		* @param t1 the first task
559		* @param t2 the second task
560		* @throws NullPointerException if any task is null
554	–	* @throws RuntimeException or Error if a task did so
561		*/
562	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
562	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
563		t2.fork();
564		t1.invoke();
565		t2.join();
#	Line 561 | Line 567 | public abstract class ForkJoinTask<V> im
567
568		/**
569		* Forks the given tasks, returning when {@code isDone} holds for
570	<	* each task or an exception is encountered. If any task
571	<	* encounters an exception, others may be, but are not guaranteed
572	<	* to be, cancelled.  This method may be invoked only from within
573	<	* ForkJoinTask computations (as may be determined using method
574	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
575	<	* result in exceptions or errors, possibly including
576	<	* ClassCastException.
577	<	*
578	<	* Overloadings of this method exist for the special cases
579	<	* of one to four arguments.
570	>	* each task or an (unchecked) exception is encountered, in which
571	>	* case the exception is rethrown. If any task encounters an
572	>	* exception, others may be, but are not guaranteed to be,
573	>	* cancelled.  If more than one task encounters an exception, then
574	>	* this method throws any one of these exceptions.  The individual
575	>	* status of each task may be checked using {@link #getException()}
576	>	* and related methods.
577	>	*
578	>	* <p>This method may be invoked only from within {@code
579	>	* ForkJoinTask} computations (as may be determined using method
580	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
581	>	* result in exceptions or errors, possibly including {@code
582	>	* ClassCastException}.
583		*
584		* @param tasks the tasks
585	<	* @throws NullPointerException if tasks or any element are null
577	<	* @throws RuntimeException or Error if any task did so
585	>	* @throws NullPointerException if any task is null
586		*/
587		public static void invokeAll(ForkJoinTask<?>... tasks) {
588		Throwable ex = null;
#	Line 610 | Line 618 | public abstract class ForkJoinTask<V> im
618		}
619
620		/**
621	<	* Forks all tasks in the collection, returning when {@code
622	<	* isDone} holds for each task or an exception is encountered. If
623	<	* any task encounters an exception, others may be, but are not
624	<	* guaranteed to be, cancelled.  This method may be invoked only
625	<	* from within ForkJoinTask computations (as may be determined
626	<	* using method {@link #inForkJoinPool}). Attempts to invoke in
627	<	* other contexts result in exceptions or errors, possibly
628	<	* including ClassCastException.
621	>	* Forks all tasks in the specified collection, returning when
622	>	* {@code isDone} holds for each task or an (unchecked) exception
623	>	* is encountered.  If any task encounters an exception, others
624	>	* may be, but are not guaranteed to be, cancelled.  If more than
625	>	* one task encounters an exception, then this method throws any
626	>	* one of these exceptions.  The individual status of each task
627	>	* may be checked using {@link #getException()} and related
628	>	* methods.  The behavior of this operation is undefined if the
629	>	* specified collection is modified while the operation is in
630	>	* progress.
631	>	*
632	>	* <p>This method may be invoked only from within {@code
633	>	* ForkJoinTask} computations (as may be determined using method
634	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
635	>	* result in exceptions or errors, possibly including {@code
636	>	* ClassCastException}.
637		*
638		* @param tasks the collection of tasks
639		* @return the tasks argument, to simplify usage
640		* @throws NullPointerException if tasks or any element are null
625	–	* @throws RuntimeException or Error if any task did so
641		*/
642		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
643	<	if (!(tasks instanceof List<?>)) {
643	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
644		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
645		return tasks;
646		}
#	Line 666 | Line 681 | public abstract class ForkJoinTask<V> im
681		}
682
683		/**
684	<	* Returns {@code true} if the computation performed by this task
685	<	* has completed (or has been cancelled).
686	<	*
687	<	* @return {@code true} if this computation has completed
688	<	*/
689	<	public final boolean isDone() {
690	<	return status < 0;
676	<	}
677	<
678	<	/**
679	<	* Returns {@code true} if this task was cancelled.
680	<	*
681	<	* @return {@code true} if this task was cancelled
682	<	*/
683	<	public final boolean isCancelled() {
684	<	return (status & COMPLETION_MASK) == CANCELLED;
685	<	}
686	<
687	<	/**
688	<	* Asserts that the results of this task's computation will not be
689	<	* used. If a cancellation occurs before attempting to execute this
690	<	* task, execution will be suppressed, {@link #isCancelled}
691	<	* will report true, and {@link #join} will result in a
692	<	* {@code CancellationException} being thrown. Otherwise, when
693	<	* cancellation races with completion, there are no guarantees
694	<	* about whether {@code isCancelled} will report {@code true},
695	<	* whether {@code join} will return normally or via an exception,
696	<	* or whether these behaviors will remain consistent upon repeated
697	<	* invocation.
684	>	* Attempts to cancel execution of this task. This attempt will
685	>	* fail if the task has already completed, has already been
686	>	* cancelled, or could not be cancelled for some other reason. If
687	>	* successful, and this task has not started when cancel is
688	>	* called, execution of this task is suppressed, {@link
689	>	* #isCancelled} will report true, and {@link #join} will result
690	>	* in a {@code CancellationException} being thrown.
691		*
692		* <p>This method may be overridden in subclasses, but if so, must
693		* still ensure that these minimal properties hold. In particular,
#	Line 706 | Line 699 | public abstract class ForkJoinTask<V> im
699		* invoke {@link #completeExceptionally}.
700		*
701		* @param mayInterruptIfRunning this value is ignored in the
702	<	* default implementation because tasks are not in general
702	>	* default implementation because tasks are not
703		* cancelled via interruption
704		*
705		* @return {@code true} if this task is now cancelled
#	Line 717 | Line 710 | public abstract class ForkJoinTask<V> im
710		}
711
712		/**
713	+	* Returns {@code true} if the computation performed by this task
714	+	* has completed (or has been cancelled).
715	+	*
716	+	* @return {@code true} if this computation has completed
717	+	*/
718	+	public final boolean isDone() {
719	+	return status < 0;
720	+	}
721	+
722	+	/**
723	+	* Returns {@code true} if this task was cancelled.
724	+	*
725	+	* @return {@code true} if this task was cancelled
726	+	*/
727	+	public final boolean isCancelled() {
728	+	return (status & COMPLETION_MASK) == CANCELLED;
729	+	}
730	+
731	+	/**
732		* Returns {@code true} if this task threw an exception or was cancelled.
733		*
734		* @return {@code true} if this task threw an exception or was cancelled
#	Line 726 | Line 738 | public abstract class ForkJoinTask<V> im
738		}
739
740		/**
741	+	* Returns {@code true} if this task completed without throwing an
742	+	* exception and was not cancelled.
743	+	*
744	+	* @return {@code true} if this task completed without throwing an
745	+	* exception and was not cancelled
746	+	*/
747	+	public final boolean isCompletedNormally() {
748	+	return (status & COMPLETION_MASK) == NORMAL;
749	+	}
750	+
751	+	/**
752	+	* Returns {@code true} if this task threw an exception.
753	+	*
754	+	* @return {@code true} if this task threw an exception
755	+	*/
756	+	public final boolean isCompletedExceptionally() {
757	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
758	+	}
759	+
760	+	/**
761		* Returns the exception thrown by the base computation, or a
762		* {@code CancellationException} if cancelled, or {@code null} if
763		* none or if the method has not yet completed.
#	Line 806 | Line 838 | public abstract class ForkJoinTask<V> im
838		* there are no potential dependencies between continuation of the
839		* current task and that of any other task that might be executed
840		* while helping. (This usually holds for pure divide-and-conquer
841	<	* tasks). This method may be invoked only from within
842	<	* ForkJoinTask computations (as may be determined using method
843	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
844	<	* result in exceptions or errors, possibly including
845	<	* ClassCastException.
841	>	* tasks).
842	>	*
843	>	* <p>This method may be invoked only from within {@code
844	>	* ForkJoinTask} computations (as may be determined using method
845	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
846	>	* result in exceptions or errors, possibly including {@code
847	>	* ClassCastException}.
848		*
849		* @return the computed result
850		*/
#	Line 823 | Line 857 | public abstract class ForkJoinTask<V> im
857
858		/**
859		* Possibly executes other tasks until this task is ready.  This
860	<	* method may be invoked only from within ForkJoinTask
861	<	* computations (as may be determined using method {@link
862	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
863	<	* in exceptions or errors, possibly including ClassCastException.
860	>	* method may be useful when processing collections of tasks when
861	>	* some have been cancelled or otherwise known to have aborted.
862	>	*
863	>	* <p>This method may be invoked only from within {@code
864	>	* ForkJoinTask} computations (as may be determined using method
865	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
866	>	* result in exceptions or errors, possibly including {@code
867	>	* ClassCastException}.
868		*/
869		public final void quietlyHelpJoin() {
870		if (status >= 0) {
#	Line 865 | Line 903 | public abstract class ForkJoinTask<V> im
903
904		/**
905		* Possibly executes tasks until the pool hosting the current task
906	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
907	<	* designs in which many tasks are forked, but none are explicitly
908	<	* joined, instead executing them until all are processed.  This
909	<	* method may be invoked only from within ForkJoinTask
910	<	* computations (as may be determined using method {@link
911	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
912	<	* in exceptions or errors, possibly including ClassCastException.
906	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
907	>	* be of use in designs in which many tasks are forked, but none
908	>	* are explicitly joined, instead executing them until all are
909	>	* processed.
910	>	*
911	>	* <p>This method may be invoked only from within {@code
912	>	* ForkJoinTask} computations (as may be determined using method
913	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
914	>	* result in exceptions or errors, possibly including {@code
915	>	* ClassCastException}.
916		*/
917		public static void helpQuiesce() {
918		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 884 | Line 925 | public abstract class ForkJoinTask<V> im
925		* this task, but only if reuse occurs when this task has either
926		* never been forked, or has been forked, then completed and all
927		* outstanding joins of this task have also completed. Effects
928	<	* under any other usage conditions are not guaranteed, and are
929	<	* discouraged. This method may be useful when executing
928	>	* under any other usage conditions are not guaranteed.
929	>	* This method may be useful when executing
930		* pre-constructed trees of subtasks in loops.
931		*/
932		public void reinitialize() {
#	Line 924 | Line 965 | public abstract class ForkJoinTask<V> im
965		* by the current thread, and has not commenced executing in
966		* another thread.  This method may be useful when arranging
967		* alternative local processing of tasks that could have been, but
968	<	* were not, stolen. This method may be invoked only from within
969	<	* ForkJoinTask computations (as may be determined using method
970	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
971	<	* result in exceptions or errors, possibly including
972	<	* ClassCastException.
968	>	* were not, stolen.
969	>	*
970	>	* <p>This method may be invoked only from within {@code
971	>	* ForkJoinTask} computations (as may be determined using method
972	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
973	>	* result in exceptions or errors, possibly including {@code
974	>	* ClassCastException}.
975		*
976		* @return {@code true} if unforked
977		*/
#	Line 941 | Line 984 | public abstract class ForkJoinTask<V> im
984		* Returns an estimate of the number of tasks that have been
985		* forked by the current worker thread but not yet executed. This
986		* value may be useful for heuristic decisions about whether to
987	<	* fork other tasks.  This method may be invoked only from within
988	<	* ForkJoinTask computations (as may be determined using method
989	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
990	<	* result in exceptions or errors, possibly including
991	<	* ClassCastException.
987	>	* fork other tasks.
988	>	*
989	>	* <p>This method may be invoked only from within {@code
990	>	* ForkJoinTask} computations (as may be determined using method
991	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
992	>	* result in exceptions or errors, possibly including {@code
993	>	* ClassCastException}.
994	>	*
995		* @return the number of tasks
996		*/
997		public static int getQueuedTaskCount() {
#	Line 961 | Line 1007 | public abstract class ForkJoinTask<V> im
1007		* usages of ForkJoinTasks, at steady state, each worker should
1008		* aim to maintain a small constant surplus (for example, 3) of
1009		* tasks, and to process computations locally if this threshold is
1010	<	* exceeded.  This method may be invoked only from within
1011	<	* ForkJoinTask computations (as may be determined using method
1012	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1013	<	* result in exceptions or errors, possibly including
1014	<	* ClassCastException.  *
1010	>	* exceeded.
1011	>	*
1012	>	* <p>This method may be invoked only from within {@code
1013	>	* ForkJoinTask} computations (as may be determined using method
1014	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1015	>	* result in exceptions or errors, possibly including {@code
1016	>	* ClassCastException}.
1017	>	*
1018		* @return the surplus number of tasks, which may be negative
1019		*/
1020		public static int getSurplusQueuedTaskCount() {
#	Line 1001 | Line 1050 | public abstract class ForkJoinTask<V> im
1050		* called otherwise. The return value controls whether this task
1051		* is considered to be done normally. It may return false in
1052		* asynchronous actions that require explicit invocations of
1053	<	* {@link #complete} to become joinable. It may throw exceptions
1054	<	* to indicate abnormal exit.
1053	>	* {@link #complete} to become joinable. It may also throw an
1054	>	* (unchecked) exception to indicate abnormal exit.
1055		*
1056		* @return {@code true} if completed normally
1008	–	* @throws Error or RuntimeException if encountered during computation
1057		*/
1058		protected abstract boolean exec();
1059
#	Line 1017 | Line 1065 | public abstract class ForkJoinTask<V> im
1065		* null even if a task exists but cannot be accessed without
1066		* contention with other threads.  This method is designed
1067		* primarily to support extensions, and is unlikely to be useful
1068	<	* otherwise.  This method may be invoked only from within
1069	<	* ForkJoinTask computations (as may be determined using method
1070	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1071	<	* result in exceptions or errors, possibly including
1072	<	* ClassCastException.
1068	>	* otherwise.
1069	>	*
1070	>	* <p>This method may be invoked only from within {@code
1071	>	* ForkJoinTask} computations (as may be determined using method
1072	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1073	>	* result in exceptions or errors, possibly including {@code
1074	>	* ClassCastException}.
1075		*
1076		* @return the next task, or {@code null} if none are available
1077		*/
#	Line 1034 | Line 1084 | public abstract class ForkJoinTask<V> im
1084		* Unschedules and returns, without executing, the next task
1085		* queued by the current thread but not yet executed.  This method
1086		* is designed primarily to support extensions, and is unlikely to
1087	<	* be useful otherwise.  This method may be invoked only from
1088	<	* within ForkJoinTask computations (as may be determined using
1089	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1090	<	* contexts result in exceptions or errors, possibly including
1091	<	* ClassCastException.
1087	>	* be useful otherwise.
1088	>	*
1089	>	* <p>This method may be invoked only from within {@code
1090	>	* ForkJoinTask} computations (as may be determined using method
1091	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1092	>	* result in exceptions or errors, possibly including {@code
1093	>	* ClassCastException}.
1094		*
1095		* @return the next task, or {@code null} if none are available
1096		*/
#	Line 1055 | Line 1107 | public abstract class ForkJoinTask<V> im
1107		* {@code null} result does not necessarily imply quiescence
1108		* of the pool this task is operating in.  This method is designed
1109		* primarily to support extensions, and is unlikely to be useful
1110	<	* otherwise.  This method may be invoked only from within
1111	<	* ForkJoinTask computations (as may be determined using method
1112	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1113	<	* result in exceptions or errors, possibly including
1114	<	* ClassCastException.
1110	>	* otherwise.
1111	>	*
1112	>	* <p>This method may be invoked only from within {@code
1113	>	* ForkJoinTask} computations (as may be determined using method
1114	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1115	>	* result in exceptions or errors, possibly including {@code
1116	>	* ClassCastException}.
1117		*
1118		* @return a task, or {@code null} if none are available
1119		*/
#	Line 1124 | Line 1178 | public abstract class ForkJoinTask<V> im
1178		}
1179
1180		/**
1181	<	* Returns a new ForkJoinTask that performs the {@code run}
1182	<	* method of the given Runnable as its action, and returns a null
1183	<	* result upon {@code join}.
1181	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1182	>	* method of the given {@code Runnable} as its action, and returns
1183	>	* a null result upon {@link #join}.
1184		*
1185		* @param runnable the runnable action
1186		* @return the task
#	Line 1136 | Line 1190 | public abstract class ForkJoinTask<V> im
1190		}
1191
1192		/**
1193	<	* Returns a new ForkJoinTask that performs the {@code run}
1194	<	* method of the given Runnable as its action, and returns the
1195	<	* given result upon {@code join}.
1193	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1194	>	* method of the given {@code Runnable} as its action, and returns
1195	>	* the given result upon {@link #join}.
1196		*
1197		* @param runnable the runnable action
1198		* @param result the result upon completion
#	Line 1149 | Line 1203 | public abstract class ForkJoinTask<V> im
1203		}
1204
1205		/**
1206	<	* Returns a new ForkJoinTask that performs the {@code call}
1207	<	* method of the given Callable as its action, and returns its
1208	<	* result upon {@code join}, translating any checked
1209	<	* exceptions encountered into {@code RuntimeException}.
1206	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1207	>	* method of the given {@code Callable} as its action, and returns
1208	>	* its result upon {@link #join}, translating any checked exceptions
1209	>	* encountered into {@code RuntimeException}.
1210		*
1211		* @param callable the callable action
1212		* @return the task

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