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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.16 by jsr166, Fri Jul 24 23:47:01 2009 UTC vs.
Revision 1.35 by dl, Tue Aug 4 12:41:27 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
10	>
11	>	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
19		/**
20	<	* Abstract base class for tasks that run within a {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22		* lighter weight than a normal thread.  Huge numbers of tasks and
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork}
30	<	* and {@code join}, or derivatives such as
31	<	* {@code invokeAll}.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
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 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.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
#	Line 61 | Line 68 | import java.util.concurrent.atomic.*;
68		* execute other tasks while awaiting joins, which is sometimes more
69		* efficient but only applies when all subtasks are known to be
70		* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76		* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	<	* <p> The ForkJoinTask class is not usually directly subclassed.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCancelled} is true if completion was due to cancellation;
84	>	* {@link #isCompletedNormally} is true if a task completed without
85	>	* cancellation or encountering an exception; {@link
86	>	* #isCompletedExceptionally} is true if if the task encountered an
87	>	* exception (in which case {@link #getException} returns the
88	>	* exception); {@link #isCancelled} is true if the task was cancelled
89	>	* (in which case {@link #getException} returns a {@link
90	>	* java.util.concurrent.CancellationException}; and {@link
91	>	* #isCompletedAbnormally} is true if a task was either cancelled or
92	>	* encountered an exception.
93	>	*
94	>	* <p>The ForkJoinTask class is not usually directly subclassed.
95		* Instead, you subclass one of the abstract classes that support a
96	<	* particular style of fork/join processing.  Normally, a concrete
96	>	* particular style of fork/join processing, typically {@link
97	>	* RecursiveAction} for computations that do not return results, or
98	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
99		* ForkJoinTask subclass declares fields comprising its parameters,
100		* established in a constructor, and then defines a {@code compute}
101		* method that somehow uses the control methods supplied by this base
102		* class. While these methods have {@code public} access (to allow
103	<	* instances of different task subclasses to call each others
103	>	* instances of different task subclasses to call each other's
104		* methods), some of them may only be called from within other
105		* ForkJoinTasks (as may be determined using method {@link
106		* #inForkJoinPool}).  Attempts to invoke them in other contexts
107		* result in exceptions or errors, possibly including
108		* ClassCastException.
109		*
110	<	* <p>Most base support methods are {@code final} because their
111	<	* implementations are intrinsically tied to the underlying
112	<	* lightweight task scheduling framework, and so cannot be overridden.
113	<	* Developers creating new basic styles of fork/join processing should
114	<	* minimally implement {@code protected} methods
115	<	* {@code exec}, {@code setRawResult}, and
116	<	* {@code getRawResult}, while also introducing an abstract
117	<	* computational method that can be implemented in its subclasses,
118	<	* possibly relying on other {@code protected} methods provided
96	<	* by this class.
110	>	* <p>Most base support methods are {@code final}, to prevent
111	>	* overriding of implementations that are intrinsically tied to the
112	>	* underlying lightweight task scheduling framework.  Developers
113	>	* creating new basic styles of fork/join processing should minimally
114	>	* implement {@code protected} methods {@link #exec}, {@link
115	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
116	>	* an abstract computational method that can be implemented in its
117	>	* subclasses, possibly relying on other {@code protected} methods
118	>	* provided by this class.
119		*
120		* <p>ForkJoinTasks should perform relatively small amounts of
121	<	* computations, otherwise splitting into smaller tasks. As a very
122	<	* rough rule of thumb, a task should perform more than 100 and less
123	<	* than 10000 basic computational steps. If tasks are too big, then
124	<	* parallelism cannot improve throughput. If too small, then memory
125	<	* and internal task maintenance overhead may overwhelm processing.
121	>	* computation. Large tasks should be split into smaller subtasks,
122	>	* usually via recursive decomposition. As a very rough rule of thumb,
123	>	* a task should perform more than 100 and less than 10000 basic
124	>	* computational steps. If tasks are too big, then parallelism cannot
125	>	* improve throughput. If too small, then memory and internal task
126	>	* maintenance overhead may overwhelm processing.
127	>	*
128	>	* <p>This class provides {@code adapt} methods for {@link
129	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
130	>	* may be of use when mixing execution of ForkJoinTasks with other
131	>	* kinds of tasks. When all tasks are of this form, consider using a
132	>	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
133		*
134	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
135	<	* to be used in extensions such as remote execution frameworks. It is
136	<	* in general sensible to serialize tasks only before or after, but
137	<	* not during execution. Serialization is not relied on during
109	<	* execution itself.
134	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
135	>	* used in extensions such as remote execution frameworks. It is
136	>	* sensible to serialize tasks only before or after, but not during,
137	>	* execution. Serialization is not relied on during execution itself.
138		*
139		* @since 1.7
140		* @author Doug Lea
#	Line 243 | Line 271 | public abstract class ForkJoinTask<V> im
271		synchronized (this) {
272		try {
273		while (status >= 0) {
274	<	long nt = nanos - System.nanoTime() - startTime;
274	>	long nt = nanos - (System.nanoTime() - startTime);
275		if (nt <= 0)
276		break;
277		wait(nt / 1000000, (int) (nt % 1000000));
#	Line 368 | Line 396 | public abstract class ForkJoinTask<V> im
396		*/
397		private V reportFutureResult()
398		throws ExecutionException, InterruptedException {
399	+	if (Thread.interrupted())
400	+	throw new InterruptedException();
401		int s = status & COMPLETION_MASK;
402		if (s < NORMAL) {
403		Throwable ex;
#	Line 375 | Line 405 | public abstract class ForkJoinTask<V> im
405		throw new CancellationException();
406		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
407		throw new ExecutionException(ex);
378	–	if (Thread.interrupted())
379	–	throw new InterruptedException();
408		}
409		return getRawResult();
410		}
#	Line 387 | Line 415 | public abstract class ForkJoinTask<V> im
415		*/
416		private V reportTimedFutureResult()
417		throws InterruptedException, ExecutionException, TimeoutException {
418	+	if (Thread.interrupted())
419	+	throw new InterruptedException();
420		Throwable ex;
421		int s = status & COMPLETION_MASK;
422		if (s == NORMAL)
#	Line 395 | Line 425 | public abstract class ForkJoinTask<V> im
425		throw new CancellationException();
426		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427		throw new ExecutionException(ex);
398	–	if (Thread.interrupted())
399	–	throw new InterruptedException();
428		throw new TimeoutException();
429		}
430
#	Line 482 | Line 510 | public abstract class ForkJoinTask<V> im
510		/**
511		* Arranges to asynchronously execute this task.  While it is not
512		* necessarily enforced, it is a usage error to fork a task more
513	<	* than once unless it has completed and been reinitialized.  This
514	<	* method may be invoked only from within ForkJoinTask
515	<	* computations (as may be determined using method {@link
516	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
517	<	* in exceptions or errors, possibly including ClassCastException.
513	>	* than once unless it has completed and been reinitialized.
514	>	*
515	>	* <p>This method may be invoked only from within {@code
516	>	* ForkJoinTask} computations (as may be determined using method
517	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
518	>	* result in exceptions or errors, possibly including {@code
519	>	* ClassCastException}.
520	>	*
521	>	* @return {@code this}, to simplify usage
522		*/
523	<	public final void fork() {
523	>	public final ForkJoinTask<V> fork() {
524		((ForkJoinWorkerThread) Thread.currentThread())
525		.pushTask(this);
526	+	return this;
527		}
528
529		/**
530		* Returns the result of the computation when it is ready.
531	<	* This method differs from {@code get} in that abnormal
532	<	* completion results in RuntimeExceptions or Errors, not
533	<	* ExecutionExceptions.
531	>	* This method differs from {@link #get()} in that
532	>	* abnormal completion results in {@code RuntimeException} or
533	>	* {@code Error}, not {@code ExecutionException}.
534		*
535		* @return the computed result
536		*/
#	Line 510 | Line 543 | public abstract class ForkJoinTask<V> im
543
544		/**
545		* Commences performing this task, awaits its completion if
546	<	* necessary, and return its result.
546	>	* necessary, and return its result, or throws an (unchecked)
547	>	* exception if the underlying computation did so.
548		*
515	–	* @throws Throwable (a RuntimeException, Error, or unchecked
516	–	* exception) if the underlying computation did so
549		* @return the computed result
550		*/
551		public final V invoke() {
#	Line 524 | Line 556 | public abstract class ForkJoinTask<V> im
556		}
557
558		/**
559	<	* Forks both tasks, returning when {@code isDone} holds for
560	<	* both of them or an exception is encountered. This method may be
561	<	* invoked only from within ForkJoinTask computations (as may be
562	<	* determined using method {@link #inForkJoinPool}). Attempts to
563	<	* invoke in other contexts result in exceptions or errors,
564	<	* possibly including ClassCastException.
565	<	*
566	<	* @param t1 one task
567	<	* @param t2 the other task
568	<	* @throws NullPointerException if t1 or t2 are null
569	<	* @throws RuntimeException or Error if either task did so
559	>	* Forks the given tasks, returning when {@code isDone} holds for
560	>	* each task or an (unchecked) exception is encountered, in which
561	>	* case the exception is rethrown.  If more than one task
562	>	* encounters an exception, then this method throws any one of
563	>	* these exceptions.  The individual status of each task may be
564	>	* checked using {@link #getException()} and related methods.
565	>	*
566	>	* <p>This method may be invoked only from within {@code
567	>	* ForkJoinTask} computations (as may be determined using method
568	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
569	>	* result in exceptions or errors, possibly including {@code
570	>	* ClassCastException}.
571	>	*
572	>	* @param t1 the first task
573	>	* @param t2 the second task
574	>	* @throws NullPointerException if any task is null
575		*/
576	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
576	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
577		t2.fork();
578		t1.invoke();
579		t2.join();
580		}
581
582		/**
583	<	* Forks the given tasks, returning when {@code isDone} holds
584	<	* for all of them. If any task encounters an exception, others
585	<	* may be cancelled.  This method may be invoked only from within
586	<	* ForkJoinTask computations (as may be determined using method
587	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
588	<	* result in exceptions or errors, possibly including
589	<	* ClassCastException.
583	>	* Forks the given tasks, returning when {@code isDone} holds for
584	>	* each task or an (unchecked) exception is encountered, in which
585	>	* case the exception is rethrown. If any task encounters an
586	>	* exception, others may be, but are not guaranteed to be,
587	>	* cancelled.  If more than one task encounters an exception, then
588	>	* this method throws any one of these exceptions.  The individual
589	>	* status of each task may be checked using {@link #getException()}
590	>	* and related methods.
591	>	*
592	>	* <p>This method may be invoked only from within {@code
593	>	* ForkJoinTask} computations (as may be determined using method
594	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
595	>	* result in exceptions or errors, possibly including {@code
596	>	* ClassCastException}.
597		*
598	<	* @param tasks the array of tasks
599	<	* @throws NullPointerException if tasks or any element are null
556	<	* @throws RuntimeException or Error if any task did so
598	>	* @param tasks the tasks
599	>	* @throws NullPointerException if any task is null
600		*/
601		public static void invokeAll(ForkJoinTask<?>... tasks) {
602		Throwable ex = null;
#	Line 589 | Line 632 | public abstract class ForkJoinTask<V> im
632		}
633
634		/**
635	<	* Forks all tasks in the collection, returning when
636	<	* {@code isDone} holds for all of them. If any task
637	<	* encounters an exception, others may be cancelled.  This method
638	<	* may be invoked only from within ForkJoinTask computations (as
639	<	* may be determined using method {@link
640	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
641	<	* in exceptions or errors, possibly including ClassCastException.
635	>	* Forks all tasks in the specified collection, returning when
636	>	* {@code isDone} holds for each task or an (unchecked) exception
637	>	* is encountered.  If any task encounters an exception, others
638	>	* may be, but are not guaranteed to be, cancelled.  If more than
639	>	* one task encounters an exception, then this method throws any
640	>	* one of these exceptions.  The individual status of each task
641	>	* may be checked using {@link #getException()} and related
642	>	* methods.  The behavior of this operation is undefined if the
643	>	* specified collection is modified while the operation is in
644	>	* progress.
645	>	*
646	>	* <p>This method may be invoked only from within {@code
647	>	* ForkJoinTask} computations (as may be determined using method
648	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
649	>	* result in exceptions or errors, possibly including {@code
650	>	* ClassCastException}.
651		*
652		* @param tasks the collection of tasks
653	+	* @return the tasks argument, to simplify usage
654		* @throws NullPointerException if tasks or any element are null
602	–	* @throws RuntimeException or Error if any task did so
655		*/
656	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
657	<	if (!(tasks instanceof List<?>)) {
656	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
657	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
658		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
659	<	return;
659	>	return tasks;
660		}
661		@SuppressWarnings("unchecked")
662		List<? extends ForkJoinTask<?>> ts =
#	Line 639 | Line 691 | public abstract class ForkJoinTask<V> im
691		}
692		if (ex != null)
693		rethrowException(ex);
694	+	return tasks;
695	+	}
696	+
697	+	/**
698	+	* Attempts to cancel execution of this task. This attempt will
699	+	* fail if the task has already completed, has already been
700	+	* cancelled, or could not be cancelled for some other reason. If
701	+	* successful, and this task has not started when cancel is
702	+	* called, execution of this task is suppressed, {@link
703	+	* #isCancelled} will report true, and {@link #join} will result
704	+	* in a {@code CancellationException} being thrown.
705	+	*
706	+	* <p>This method may be overridden in subclasses, but if so, must
707	+	* still ensure that these minimal properties hold. In particular,
708	+	* the {@code cancel} method itself must not throw exceptions.
709	+	*
710	+	* <p>This method is designed to be invoked by <em>other</em>
711	+	* tasks. To terminate the current task, you can just return or
712	+	* throw an unchecked exception from its computation method, or
713	+	* invoke {@link #completeExceptionally}.
714	+	*
715	+	* @param mayInterruptIfRunning this value is ignored in the
716	+	* default implementation because tasks are not
717	+	* cancelled via interruption
718	+	*
719	+	* @return {@code true} if this task is now cancelled
720	+	*/
721	+	public boolean cancel(boolean mayInterruptIfRunning) {
722	+	setCompletion(CANCELLED);
723	+	return (status & COMPLETION_MASK) == CANCELLED;
724		}
725
726		/**
727	<	* Returns true if the computation performed by this task has
728	<	* completed (or has been cancelled).
727	>	* Returns {@code true} if the computation performed by this task
728	>	* has completed (or has been cancelled).
729		*
730	<	* @return true if this computation has completed
730	>	* @return {@code true} if this computation has completed
731		*/
732		public final boolean isDone() {
733		return status < 0;
734		}
735
736		/**
737	<	* Returns true if this task was cancelled.
737	>	* Returns {@code true} if this task was cancelled.
738		*
739	<	* @return true if this task was cancelled
739	>	* @return {@code true} if this task was cancelled
740		*/
741		public final boolean isCancelled() {
742		return (status & COMPLETION_MASK) == CANCELLED;
743		}
744
745		/**
746	<	* Asserts that the results of this task's computation will not be
665	<	* used. If a cancellation occurs before attempting to execute this
666	<	* task, then execution will be suppressed, {@code isCancelled}
667	<	* will report true, and {@code join} will result in a
668	<	* {@code CancellationException} being thrown. Otherwise, when
669	<	* cancellation races with completion, there are no guarantees
670	<	* about whether {@code isCancelled} will report true, whether
671	<	* {@code join} will return normally or via an exception, or
672	<	* whether these behaviors will remain consistent upon repeated
673	<	* invocation.
674	<	*
675	<	* <p>This method may be overridden in subclasses, but if so, must
676	<	* still ensure that these minimal properties hold. In particular,
677	<	* the cancel method itself must not throw exceptions.
678	<	*
679	<	* <p> This method is designed to be invoked by <em>other</em>
680	<	* tasks. To terminate the current task, you can just return or
681	<	* throw an unchecked exception from its computation method, or
682	<	* invoke {@code completeExceptionally}.
746	>	* Returns {@code true} if this task threw an exception or was cancelled.
747		*
748	<	* @param mayInterruptIfRunning this value is ignored in the
749	<	* default implementation because tasks are not in general
750	<	* cancelled via interruption
748	>	* @return {@code true} if this task threw an exception or was cancelled
749	>	*/
750	>	public final boolean isCompletedAbnormally() {
751	>	return (status & COMPLETION_MASK) < NORMAL;
752	>	}
753	>
754	>	/**
755	>	* Returns {@code true} if this task completed without throwing an
756	>	* exception and was not cancelled.
757		*
758	<	* @return true if this task is now cancelled
758	>	* @return {@code true} if this task completed without throwing an
759	>	* exception and was not cancelled
760		*/
761	<	public boolean cancel(boolean mayInterruptIfRunning) {
762	<	setCompletion(CANCELLED);
692	<	return (status & COMPLETION_MASK) == CANCELLED;
761	>	public final boolean isCompletedNormally() {
762	>	return (status & COMPLETION_MASK) == NORMAL;
763		}
764
765		/**
766	<	* Returns true if this task threw an exception or was cancelled.
766	>	* Returns {@code true} if this task threw an exception.
767		*
768	<	* @return true if this task threw an exception or was cancelled
768	>	* @return {@code true} if this task threw an exception
769		*/
770	<	public final boolean isCompletedAbnormally() {
771	<	return (status & COMPLETION_MASK) < NORMAL;
770	>	public final boolean isCompletedExceptionally() {
771	>	return (status & COMPLETION_MASK) == EXCEPTIONAL;
772		}
773
774		/**
775		* Returns the exception thrown by the base computation, or a
776	<	* CancellationException if cancelled, or null if none or if the
777	<	* method has not yet completed.
776	>	* {@code CancellationException} if cancelled, or {@code null} if
777	>	* none or if the method has not yet completed.
778		*
779	<	* @return the exception, or null if none
779	>	* @return the exception, or {@code null} if none
780		*/
781		public final Throwable getException() {
782		int s = status & COMPLETION_MASK;
#	Line 723 | Line 793 | public abstract class ForkJoinTask<V> im
793		* {@code join} and related operations. This method may be used
794		* to induce exceptions in asynchronous tasks, or to force
795		* completion of tasks that would not otherwise complete.  Its use
796	<	* in other situations is likely to be wrong.  This method is
796	>	* in other situations is discouraged.  This method is
797		* overridable, but overridden versions must invoke {@code super}
798		* implementation to maintain guarantees.
799		*
#	Line 743 | Line 813 | public abstract class ForkJoinTask<V> im
813		* operations. This method may be used to provide results for
814		* asynchronous tasks, or to provide alternative handling for
815		* tasks that would not otherwise complete normally. Its use in
816	<	* other situations is likely to be wrong. This method is
816	>	* other situations is discouraged. This method is
817		* overridable, but overridden versions must invoke {@code super}
818		* implementation to maintain guarantees.
819		*
#	Line 768 | Line 838 | public abstract class ForkJoinTask<V> im
838
839		public final V get(long timeout, TimeUnit unit)
840		throws InterruptedException, ExecutionException, TimeoutException {
841	+	long nanos = unit.toNanos(timeout);
842		ForkJoinWorkerThread w = getWorker();
843		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
844	<	awaitDone(w, unit.toNanos(timeout));
844	>	awaitDone(w, nanos);
845		return reportTimedFutureResult();
846		}
847
#	Line 781 | Line 852 | public abstract class ForkJoinTask<V> im
852		* there are no potential dependencies between continuation of the
853		* current task and that of any other task that might be executed
854		* while helping. (This usually holds for pure divide-and-conquer
855	<	* tasks). This method may be invoked only from within
856	<	* ForkJoinTask computations (as may be determined using method
857	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
858	<	* result in exceptions or errors, possibly including
859	<	* ClassCastException.
855	>	* tasks).
856	>	*
857	>	* <p>This method may be invoked only from within {@code
858	>	* ForkJoinTask} computations (as may be determined using method
859	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
860	>	* result in exceptions or errors, possibly including {@code
861	>	* ClassCastException}.
862		*
863		* @return the computed result
864		*/
#	Line 798 | Line 871 | public abstract class ForkJoinTask<V> im
871
872		/**
873		* Possibly executes other tasks until this task is ready.  This
874	<	* method may be invoked only from within ForkJoinTask
875	<	* computations (as may be determined using method {@link
876	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
877	<	* in exceptions or errors, possibly including ClassCastException.
874	>	* method may be useful when processing collections of tasks when
875	>	* some have been cancelled or otherwise known to have aborted.
876	>	*
877	>	* <p>This method may be invoked only from within {@code
878	>	* ForkJoinTask} computations (as may be determined using method
879	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
880	>	* result in exceptions or errors, possibly including {@code
881	>	* ClassCastException}.
882		*/
883		public final void quietlyHelpJoin() {
884		if (status >= 0) {
#	Line 840 | Line 917 | public abstract class ForkJoinTask<V> im
917
918		/**
919		* Possibly executes tasks until the pool hosting the current task
920	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
921	<	* designs in which many tasks are forked, but none are explicitly
922	<	* joined, instead executing them until all are processed.
920	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
921	>	* be of use in designs in which many tasks are forked, but none
922	>	* are explicitly joined, instead executing them until all are
923	>	* processed.
924	>	*
925	>	* <p>This method may be invoked only from within {@code
926	>	* ForkJoinTask} computations (as may be determined using method
927	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
928	>	* result in exceptions or errors, possibly including {@code
929	>	* ClassCastException}.
930		*/
931		public static void helpQuiesce() {
932		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 855 | Line 939 | public abstract class ForkJoinTask<V> im
939		* this task, but only if reuse occurs when this task has either
940		* never been forked, or has been forked, then completed and all
941		* outstanding joins of this task have also completed. Effects
942	<	* under any other usage conditions are not guaranteed, and are
943	<	* almost surely wrong. This method may be useful when executing
942	>	* under any other usage conditions are not guaranteed.
943	>	* This method may be useful when executing
944		* pre-constructed trees of subtasks in loops.
945		*/
946		public void reinitialize() {
#	Line 869 | Line 953 | public abstract class ForkJoinTask<V> im
953		* Returns the pool hosting the current task execution, or null
954		* if this task is executing outside of any ForkJoinPool.
955		*
956	<	* @return the pool, or null if none
956	>	* @see #inForkJoinPool
957	>	* @return the pool, or {@code null} if none
958		*/
959		public static ForkJoinPool getPool() {
960		Thread t = Thread.currentThread();
#	Line 894 | Line 979 | public abstract class ForkJoinTask<V> im
979		* by the current thread, and has not commenced executing in
980		* another thread.  This method may be useful when arranging
981		* alternative local processing of tasks that could have been, but
982	<	* were not, stolen. This method may be invoked only from within
983	<	* ForkJoinTask computations (as may be determined using method
984	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
985	<	* result in exceptions or errors, possibly including
986	<	* ClassCastException.
982	>	* were not, stolen.
983	>	*
984	>	* <p>This method may be invoked only from within {@code
985	>	* ForkJoinTask} computations (as may be determined using method
986	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
987	>	* result in exceptions or errors, possibly including {@code
988	>	* ClassCastException}.
989		*
990	<	* @return true if unforked
990	>	* @return {@code true} if unforked
991		*/
992		public boolean tryUnfork() {
993		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 913 | Line 1000 | public abstract class ForkJoinTask<V> im
1000		* value may be useful for heuristic decisions about whether to
1001		* fork other tasks.
1002		*
1003	+	* <p>This method may be invoked only from within {@code
1004	+	* ForkJoinTask} computations (as may be determined using method
1005	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1006	+	* result in exceptions or errors, possibly including {@code
1007	+	* ClassCastException}.
1008	+	*
1009		* @return the number of tasks
1010		*/
1011		public static int getQueuedTaskCount() {
#	Line 930 | Line 1023 | public abstract class ForkJoinTask<V> im
1023		* tasks, and to process computations locally if this threshold is
1024		* exceeded.
1025		*
1026	+	* <p>This method may be invoked only from within {@code
1027	+	* ForkJoinTask} computations (as may be determined using method
1028	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1029	+	* result in exceptions or errors, possibly including {@code
1030	+	* ClassCastException}.
1031	+	*
1032		* @return the surplus number of tasks, which may be negative
1033		*/
1034		public static int getSurplusQueuedTaskCount() {
#	Line 940 | Line 1039 | public abstract class ForkJoinTask<V> im
1039		// Extension methods
1040
1041		/**
1042	<	* Returns the result that would be returned by {@code join},
1043	<	* even if this task completed abnormally, or null if this task is
1044	<	* not known to have been completed.  This method is designed to
1045	<	* aid debugging, as well as to support extensions. Its use in any
1046	<	* other context is discouraged.
1042	>	* Returns the result that would be returned by {@link #join}, even
1043	>	* if this task completed abnormally, or {@code null} if this task
1044	>	* is not known to have been completed.  This method is designed
1045	>	* to aid debugging, as well as to support extensions. Its use in
1046	>	* any other context is discouraged.
1047		*
1048	<	* @return the result, or null if not completed
1048	>	* @return the result, or {@code null} if not completed
1049		*/
1050		public abstract V getRawResult();
1051
#	Line 965 | Line 1064 | public abstract class ForkJoinTask<V> im
1064		* called otherwise. The return value controls whether this task
1065		* is considered to be done normally. It may return false in
1066		* asynchronous actions that require explicit invocations of
1067	<	* {@code complete} to become joinable. It may throw exceptions
1068	<	* to indicate abnormal exit.
1067	>	* {@link #complete} to become joinable. It may also throw an
1068	>	* (unchecked) exception to indicate abnormal exit.
1069		*
1070	<	* @return true if completed normally
972	<	* @throws Error or RuntimeException if encountered during computation
1070	>	* @return {@code true} if completed normally
1071		*/
1072		protected abstract boolean exec();
1073
1074		/**
1075	<	* Returns, but does not unschedule or execute, the task queued by
1076	<	* the current thread but not yet executed, if one is
1075	>	* Returns, but does not unschedule or execute, a task queued by
1076	>	* the current thread but not yet executed, if one is immediately
1077		* available. There is no guarantee that this task will actually
1078	<	* be polled or executed next.  This method is designed primarily
1079	<	* to support extensions, and is unlikely to be useful otherwise.
1080	<	* This method may be invoked only from within ForkJoinTask
1081	<	* computations (as may be determined using method {@link
1082	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
1083	<	* in exceptions or errors, possibly including ClassCastException.
1078	>	* be polled or executed next. Conversely, this method may return
1079	>	* null even if a task exists but cannot be accessed without
1080	>	* contention with other threads.  This method is designed
1081	>	* primarily to support extensions, and is unlikely to be useful
1082	>	* otherwise.
1083	>	*
1084	>	* <p>This method may be invoked only from within {@code
1085	>	* ForkJoinTask} computations (as may be determined using method
1086	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1087	>	* result in exceptions or errors, possibly including {@code
1088	>	* ClassCastException}.
1089		*
1090	<	* @return the next task, or null if none are available
1090	>	* @return the next task, or {@code null} if none are available
1091		*/
1092		protected static ForkJoinTask<?> peekNextLocalTask() {
1093		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 995 | Line 1098 | public abstract class ForkJoinTask<V> im
1098		* Unschedules and returns, without executing, the next task
1099		* queued by the current thread but not yet executed.  This method
1100		* is designed primarily to support extensions, and is unlikely to
1101	<	* be useful otherwise.  This method may be invoked only from
999	<	* within ForkJoinTask computations (as may be determined using
1000	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1001	<	* contexts result in exceptions or errors, possibly including
1002	<	* ClassCastException.
1101	>	* be useful otherwise.
1102		*
1103	<	* @return the next task, or null if none are available
1103	>	* <p>This method may be invoked only from within {@code
1104	>	* ForkJoinTask} computations (as may be determined using method
1105	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1106	>	* result in exceptions or errors, possibly including {@code
1107	>	* ClassCastException}.
1108	>	*
1109	>	* @return the next task, or {@code null} if none are available
1110		*/
1111		protected static ForkJoinTask<?> pollNextLocalTask() {
1112		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1016 | Line 1121 | public abstract class ForkJoinTask<V> im
1121		* {@code null} result does not necessarily imply quiescence
1122		* of the pool this task is operating in.  This method is designed
1123		* primarily to support extensions, and is unlikely to be useful
1124	<	* otherwise.  This method may be invoked only from within
1125	<	* ForkJoinTask computations (as may be determined using method
1126	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1127	<	* result in exceptions or errors, possibly including
1128	<	* ClassCastException.
1124	>	* otherwise.
1125	>	*
1126	>	* <p>This method may be invoked only from within {@code
1127	>	* ForkJoinTask} computations (as may be determined using method
1128	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1129	>	* result in exceptions or errors, possibly including {@code
1130	>	* ClassCastException}.
1131		*
1132	<	* @return a task, or null if none are available
1132	>	* @return a task, or {@code null} if none are available
1133		*/
1134		protected static ForkJoinTask<?> pollTask() {
1135		return ((ForkJoinWorkerThread) Thread.currentThread())
1136		.pollTask();
1137		}
1138
1139	+	/**
1140	+	* Adaptor for Runnables. This implements RunnableFuture
1141	+	* to be compliant with AbstractExecutorService constraints
1142	+	* when used in ForkJoinPool.
1143	+	*/
1144	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1145	+	implements RunnableFuture<T> {
1146	+	final Runnable runnable;
1147	+	final T resultOnCompletion;
1148	+	T result;
1149	+	AdaptedRunnable(Runnable runnable, T result) {
1150	+	if (runnable == null) throw new NullPointerException();
1151	+	this.runnable = runnable;
1152	+	this.resultOnCompletion = result;
1153	+	}
1154	+	public T getRawResult() { return result; }
1155	+	public void setRawResult(T v) { result = v; }
1156	+	public boolean exec() {
1157	+	runnable.run();
1158	+	result = resultOnCompletion;
1159	+	return true;
1160	+	}
1161	+	public void run() { invoke(); }
1162	+	private static final long serialVersionUID = 5232453952276885070L;
1163	+	}
1164	+
1165	+	/**
1166	+	* Adaptor for Callables
1167	+	*/
1168	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1169	+	implements RunnableFuture<T> {
1170	+	final Callable<? extends T> callable;
1171	+	T result;
1172	+	AdaptedCallable(Callable<? extends T> callable) {
1173	+	if (callable == null) throw new NullPointerException();
1174	+	this.callable = callable;
1175	+	}
1176	+	public T getRawResult() { return result; }
1177	+	public void setRawResult(T v) { result = v; }
1178	+	public boolean exec() {
1179	+	try {
1180	+	result = callable.call();
1181	+	return true;
1182	+	} catch (Error err) {
1183	+	throw err;
1184	+	} catch (RuntimeException rex) {
1185	+	throw rex;
1186	+	} catch (Exception ex) {
1187	+	throw new RuntimeException(ex);
1188	+	}
1189	+	}
1190	+	public void run() { invoke(); }
1191	+	private static final long serialVersionUID = 2838392045355241008L;
1192	+	}
1193	+
1194	+	/**
1195	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1196	+	* method of the given {@code Runnable} as its action, and returns
1197	+	* a null result upon {@link #join}.
1198	+	*
1199	+	* @param runnable the runnable action
1200	+	* @return the task
1201	+	*/
1202	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1203	+	return new AdaptedRunnable<Void>(runnable, null);
1204	+	}
1205	+
1206	+	/**
1207	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1208	+	* method of the given {@code Runnable} as its action, and returns
1209	+	* the given result upon {@link #join}.
1210	+	*
1211	+	* @param runnable the runnable action
1212	+	* @param result the result upon completion
1213	+	* @return the task
1214	+	*/
1215	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1216	+	return new AdaptedRunnable<T>(runnable, result);
1217	+	}
1218	+
1219	+	/**
1220	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1221	+	* method of the given {@code Callable} as its action, and returns
1222	+	* its result upon {@link #join}, translating any checked exceptions
1223	+	* encountered into {@code RuntimeException}.
1224	+	*
1225	+	* @param callable the callable action
1226	+	* @return the task
1227	+	*/
1228	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1229	+	return new AdaptedCallable<T>(callable);
1230	+	}
1231	+
1232		// Serialization support
1233
1234		private static final long serialVersionUID = -7721805057305804111L;
#	Line 1037 | Line 1237 | public abstract class ForkJoinTask<V> im
1237		* Save the state to a stream.
1238		*
1239		* @serialData the current run status and the exception thrown
1240	<	* during execution, or null if none
1240	>	* during execution, or {@code null} if none
1241		* @param s the stream
1242		*/
1243		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1061 | Line 1261 | public abstract class ForkJoinTask<V> im
1261		setDoneExceptionally((Throwable) ex);
1262		}
1263
1264	<	// Unsafe mechanics for jsr166y 3rd party package.
1264	>	// Unsafe mechanics
1265	>
1266	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1267	>	private static final long statusOffset =
1268	>	objectFieldOffset("status", ForkJoinTask.class);
1269	>
1270	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1271	>	try {
1272	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1273	>	} catch (NoSuchFieldException e) {
1274	>	// Convert Exception to corresponding Error
1275	>	NoSuchFieldError error = new NoSuchFieldError(field);
1276	>	error.initCause(e);
1277	>	throw error;
1278	>	}
1279	>	}
1280	>
1281	>	/**
1282	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1283	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1284	>	* into a jdk.
1285	>	*
1286	>	* @return a sun.misc.Unsafe
1287	>	*/
1288		private static sun.misc.Unsafe getUnsafe() {
1289		try {
1290		return sun.misc.Unsafe.getUnsafe();
1291		} catch (SecurityException se) {
1292		try {
1293		return java.security.AccessController.doPrivileged
1294	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1294	>	(new java.security
1295	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1296		public sun.misc.Unsafe run() throws Exception {
1297	<	return getUnsafeByReflection();
1297	>	java.lang.reflect.Field f = sun.misc
1298	>	.Unsafe.class.getDeclaredField("theUnsafe");
1299	>	f.setAccessible(true);
1300	>	return (sun.misc.Unsafe) f.get(null);
1301		}});
1302		} catch (java.security.PrivilegedActionException e) {
1303		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1078 | Line 1305 | public abstract class ForkJoinTask<V> im
1305		}
1306		}
1307		}
1081	–
1082	–	private static sun.misc.Unsafe getUnsafeByReflection()
1083	–	throws NoSuchFieldException, IllegalAccessException {
1084	–	java.lang.reflect.Field f =
1085	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1086	–	f.setAccessible(true);
1087	–	return (sun.misc.Unsafe) f.get(null);
1088	–	}
1089	–
1090	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1091	–	try {
1092	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1093	–	} catch (NoSuchFieldException e) {
1094	–	// Convert Exception to Error
1095	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1096	–	error.initCause(e);
1097	–	throw error;
1098	–	}
1099	–	}
1100	–
1101	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1102	–	static final long statusOffset =
1103	–	fieldOffset("status", ForkJoinTask.class);
1104	–
1308		}

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