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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.22 by jsr166, Sun Jul 26 17:33:37 2009 UTC vs.
Revision 1.44 by jsr166, Wed Aug 19 17:44:45 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
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 {@link RejectedExecutionException} stemming
60	>	* from internal resource exhaustion, such as failure to allocate
61	>	* internal 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 66 | Line 68 | import java.util.WeakHashMap;
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 #isCompletedNormally} is true if a task completed without
84	>	* cancellation or encountering an exception; {@link #isCancelled} is
85	>	* true if the task was cancelled (in which case {@link #getException}
86	>	* returns a {@link java.util.concurrent.CancellationException}); and
87	>	* {@link #isCompletedAbnormally} is true if a task was either
88	>	* cancelled or encountered an exception, in which case {@link
89	>	* #getException} will return either the encountered exception or
90	>	* {@link java.util.concurrent.CancellationException}.
91	>	*
92	>	* <p>The ForkJoinTask class is not usually directly subclassed.
93		* Instead, you subclass one of the abstract classes that support a
94	<	* particular style of fork/join processing.  Normally, a concrete
94	>	* particular style of fork/join processing, typically {@link
95	>	* RecursiveAction} for computations that do not return results, or
96	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
97		* ForkJoinTask subclass declares fields comprising its parameters,
98		* established in a constructor, and then defines a {@code compute}
99		* method that somehow uses the control methods supplied by this base
100		* class. While these methods have {@code public} access (to allow
101	<	* instances of different task subclasses to call each others
101	>	* instances of different task subclasses to call each other's
102		* methods), some of them may only be called from within other
103		* ForkJoinTasks (as may be determined using method {@link
104		* #inForkJoinPool}).  Attempts to invoke them in other contexts
105		* result in exceptions or errors, possibly including
106		* ClassCastException.
107		*
108	<	* <p>Most base support methods are {@code final} because their
109	<	* implementations are intrinsically tied to the underlying
110	<	* lightweight task scheduling framework, and so cannot be overridden.
111	<	* Developers creating new basic styles of fork/join processing should
112	<	* minimally implement {@code protected} methods
113	<	* {@code exec}, {@code setRawResult}, and
114	<	* {@code getRawResult}, while also introducing an abstract
115	<	* computational method that can be implemented in its subclasses,
116	<	* possibly relying on other {@code protected} methods provided
101	<	* by this class.
108	>	* <p>Most base support methods are {@code final}, to prevent
109	>	* overriding of implementations that are intrinsically tied to the
110	>	* underlying lightweight task scheduling framework.  Developers
111	>	* creating new basic styles of fork/join processing should minimally
112	>	* implement {@code protected} methods {@link #exec}, {@link
113	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
114	>	* an abstract computational method that can be implemented in its
115	>	* subclasses, possibly relying on other {@code protected} methods
116	>	* provided by this class.
117		*
118		* <p>ForkJoinTasks should perform relatively small amounts of
119	<	* computations, otherwise splitting into smaller tasks. As a very
120	<	* rough rule of thumb, a task should perform more than 100 and less
121	<	* than 10000 basic computational steps. If tasks are too big, then
122	<	* parallelism cannot improve throughput. If too small, then memory
123	<	* and internal task maintenance overhead may overwhelm processing.
119	>	* computation. Large tasks should be split into smaller subtasks,
120	>	* usually via recursive decomposition. As a very rough rule of thumb,
121	>	* a task should perform more than 100 and less than 10000 basic
122	>	* computational steps. If tasks are too big, then parallelism cannot
123	>	* improve throughput. If too small, then memory and internal task
124	>	* maintenance overhead may overwhelm processing.
125	>	*
126	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
127	>	* and {@link Callable}, that may be of use when mixing execution of
128	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
129	>	* are of this form, consider using a pool in
130	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
131		*
132	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
133	<	* to be used in extensions such as remote execution frameworks. It is
134	<	* in general sensible to serialize tasks only before or after, but
135	<	* not during execution. Serialization is not relied on during
114	<	* execution itself.
132	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
133	>	* used in extensions such as remote execution frameworks. It is
134	>	* sensible to serialize tasks only before or after, but not during,
135	>	* execution. Serialization is not relied on during execution itself.
136		*
137		* @since 1.7
138		* @author Doug Lea
#	Line 248 | Line 269 | public abstract class ForkJoinTask<V> im
269		synchronized (this) {
270		try {
271		while (status >= 0) {
272	<	long nt = nanos - System.nanoTime() - startTime;
272	>	long nt = nanos - (System.nanoTime() - startTime);
273		if (nt <= 0)
274		break;
275		wait(nt / 1000000, (int) (nt % 1000000));
#	Line 369 | Line 390 | public abstract class ForkJoinTask<V> im
390
391		/**
392		* Returns result or throws exception using j.u.c.Future conventions.
393	<	* Only call when {@code isDone} known to be true.
393	>	* Only call when {@code isDone} known to be true or thread known
394	>	* to be interrupted.
395		*/
396		private V reportFutureResult()
397	<	throws ExecutionException, InterruptedException {
397	>	throws InterruptedException, ExecutionException {
398	>	if (Thread.interrupted())
399	>	throw new InterruptedException();
400		int s = status & COMPLETION_MASK;
401		if (s < NORMAL) {
402		Throwable ex;
#	Line 380 | Line 404 | public abstract class ForkJoinTask<V> im
404		throw new CancellationException();
405		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
406		throw new ExecutionException(ex);
383	–	if (Thread.interrupted())
384	–	throw new InterruptedException();
407		}
408		return getRawResult();
409		}
#	Line 392 | Line 414 | public abstract class ForkJoinTask<V> im
414		*/
415		private V reportTimedFutureResult()
416		throws InterruptedException, ExecutionException, TimeoutException {
417	+	if (Thread.interrupted())
418	+	throw new InterruptedException();
419		Throwable ex;
420		int s = status & COMPLETION_MASK;
421		if (s == NORMAL)
422		return getRawResult();
423	<	if (s == CANCELLED)
423	>	else if (s == CANCELLED)
424		throw new CancellationException();
425	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
425	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426		throw new ExecutionException(ex);
427	<	if (Thread.interrupted())
428	<	throw new InterruptedException();
405	<	throw new TimeoutException();
427	>	else
428	>	throw new TimeoutException();
429		}
430
431		// internal execution methods
#	Line 487 | 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	>	* Subsequent modifications to the state of this task or any data
515	>	* it operates on are not necessarily consistently observable by
516	>	* any thread other than the one executing it unless preceded by a
517	>	* call to {@link #join} or related methods, or a call to {@link
518	>	* #isDone} returning {@code true}.
519	>	*
520	>	* <p>This method may be invoked only from within {@code
521	>	* ForkJoinTask} computations (as may be determined using method
522	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
523	>	* result in exceptions or errors, possibly including {@code
524	>	* ClassCastException}.
525		*
526	<	* @return {@code this}, to simplify usage.
526	>	* @return {@code this}, to simplify usage
527		*/
528		public final ForkJoinTask<V> fork() {
529		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 502 | Line 532 | public abstract class ForkJoinTask<V> im
532		}
533
534		/**
535	<	* Returns the result of the computation when it is ready.
536	<	* This method differs from {@code get} in that abnormal
537	<	* completion results in RuntimeExceptions or Errors, not
538	<	* ExecutionExceptions.
535	>	* Returns the result of the computation when it {@link #isDone is done}.
536	>	* This method differs from {@link #get()} in that
537	>	* abnormal completion results in {@code RuntimeException} or
538	>	* {@code Error}, not {@code ExecutionException}.
539		*
540		* @return the computed result
541		*/
#	Line 518 | Line 548 | public abstract class ForkJoinTask<V> im
548
549		/**
550		* Commences performing this task, awaits its completion if
551	<	* necessary, and return its result.
551	>	* necessary, and return its result, or throws an (unchecked)
552	>	* exception if the underlying computation did so.
553		*
523	–	* @throws Throwable (a RuntimeException, Error, or unchecked
524	–	* exception) if the underlying computation did so
554		* @return the computed result
555		*/
556		public final V invoke() {
#	Line 532 | Line 561 | public abstract class ForkJoinTask<V> im
561		}
562
563		/**
564	<	* Forks both tasks, returning when {@code isDone} holds for
565	<	* both of them or an exception is encountered. This method may be
566	<	* invoked only from within ForkJoinTask computations (as may be
567	<	* determined using method {@link #inForkJoinPool}). Attempts to
568	<	* invoke in other contexts result in exceptions or errors,
569	<	* possibly including ClassCastException.
570	<	*
571	<	* @param t1 one task
572	<	* @param t2 the other task
573	<	* @throws NullPointerException if t1 or t2 are null
574	<	* @throws RuntimeException or Error if either task did so
564	>	* Forks the given tasks, returning when {@code isDone} holds for
565	>	* each task or an (unchecked) exception is encountered, in which
566	>	* case the exception is rethrown.  If either task encounters an
567	>	* exception, the other one may be, but is not guaranteed to be,
568	>	* cancelled.  If both tasks throw an exception, then this method
569	>	* throws one of them.  The individual status of each task may be
570	>	* checked using {@link #getException()} and related methods.
571	>	*
572	>	* <p>This method may be invoked only from within {@code
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 {@code
576	>	* ClassCastException}.
577	>	*
578	>	* @param t1 the first task
579	>	* @param t2 the second task
580	>	* @throws NullPointerException if any task is null
581		*/
582	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
582	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
583		t2.fork();
584		t1.invoke();
585		t2.join();
586		}
587
588		/**
589	<	* Forks the given tasks, returning when {@code isDone} holds
590	<	* for all of them. If any task encounters an exception, others
591	<	* may be cancelled.  This method may be invoked only from within
592	<	* ForkJoinTask computations (as may be determined using method
593	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
594	<	* result in exceptions or errors, possibly including
595	<	* ClassCastException.
589	>	* Forks the given tasks, returning when {@code isDone} holds for
590	>	* each task or an (unchecked) exception is encountered, in which
591	>	* case the exception is rethrown. If any task encounters an
592	>	* exception, others may be, but are not guaranteed to be,
593	>	* cancelled.  If more than one task encounters an exception, then
594	>	* this method throws any one of these exceptions.  The individual
595	>	* status of each task may be checked using {@link #getException()}
596	>	* and related methods.
597	>	*
598	>	* <p>This method may be invoked only from within {@code
599	>	* ForkJoinTask} computations (as may be determined using method
600	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
601	>	* result in exceptions or errors, possibly including {@code
602	>	* ClassCastException}.
603		*
604	<	* @param tasks the array of tasks
605	<	* @throws NullPointerException if tasks or any element are null
564	<	* @throws RuntimeException or Error if any task did so
604	>	* @param tasks the tasks
605	>	* @throws NullPointerException if any task is null
606		*/
607		public static void invokeAll(ForkJoinTask<?>... tasks) {
608		Throwable ex = null;
#	Line 597 | Line 638 | public abstract class ForkJoinTask<V> im
638		}
639
640		/**
641	<	* Forks all tasks in the collection, returning when
642	<	* {@code isDone} holds for all of them. If any task
643	<	* encounters an exception, others may be cancelled.  This method
644	<	* may be invoked only from within ForkJoinTask computations (as
645	<	* may be determined using method {@link
646	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
647	<	* in exceptions or errors, possibly including ClassCastException.
641	>	* Forks all tasks in the specified collection, returning when
642	>	* {@code isDone} holds for each task or an (unchecked) exception
643	>	* is encountered.  If any task encounters an exception, others
644	>	* may be, but are not guaranteed to be, cancelled.  If more than
645	>	* one task encounters an exception, then this method throws any
646	>	* one of these exceptions.  The individual status of each task
647	>	* may be checked using {@link #getException()} and related
648	>	* methods.  The behavior of this operation is undefined if the
649	>	* specified collection is modified while the operation is in
650	>	* progress.
651	>	*
652	>	* <p>This method may be invoked only from within {@code
653	>	* ForkJoinTask} computations (as may be determined using method
654	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
655	>	* result in exceptions or errors, possibly including {@code
656	>	* ClassCastException}.
657		*
658		* @param tasks the collection of tasks
659		* @return the tasks argument, to simplify usage
660		* @throws NullPointerException if tasks or any element are null
611	–	* @throws RuntimeException or Error if any task did so
661		*/
662		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
663	<	if (!(tasks instanceof List<?>)) {
663	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
664		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
665		return tasks;
666		}
#	Line 652 | Line 701 | public abstract class ForkJoinTask<V> im
701		}
702
703		/**
704	<	* Returns true if the computation performed by this task has
705	<	* completed (or has been cancelled).
706	<	*
707	<	* @return true if this computation has completed
708	<	*/
709	<	public final boolean isDone() {
710	<	return status < 0;
662	<	}
663	<
664	<	/**
665	<	* Returns true if this task was cancelled.
666	<	*
667	<	* @return true if this task was cancelled
668	<	*/
669	<	public final boolean isCancelled() {
670	<	return (status & COMPLETION_MASK) == CANCELLED;
671	<	}
672	<
673	<	/**
674	<	* Asserts that the results of this task's computation will not be
675	<	* used. If a cancellation occurs before attempting to execute this
676	<	* task, then execution will be suppressed, {@code isCancelled}
677	<	* will report true, and {@code join} will result in a
678	<	* {@code CancellationException} being thrown. Otherwise, when
679	<	* cancellation races with completion, there are no guarantees
680	<	* about whether {@code isCancelled} will report true, whether
681	<	* {@code join} will return normally or via an exception, or
682	<	* whether these behaviors will remain consistent upon repeated
683	<	* invocation.
704	>	* Attempts to cancel execution of this task. This attempt will
705	>	* fail if the task has already completed, has already been
706	>	* cancelled, or could not be cancelled for some other reason. If
707	>	* successful, and this task has not started when cancel is
708	>	* called, execution of this task is suppressed, {@link
709	>	* #isCancelled} will report true, and {@link #join} will result
710	>	* in a {@code CancellationException} being thrown.
711		*
712		* <p>This method may be overridden in subclasses, but if so, must
713		* still ensure that these minimal properties hold. In particular,
714	<	* the cancel method itself must not throw exceptions.
714	>	* the {@code cancel} method itself must not throw exceptions.
715		*
716	<	* <p> This method is designed to be invoked by <em>other</em>
716	>	* <p>This method is designed to be invoked by <em>other</em>
717		* tasks. To terminate the current task, you can just return or
718		* throw an unchecked exception from its computation method, or
719	<	* invoke {@code completeExceptionally}.
719	>	* invoke {@link #completeExceptionally}.
720		*
721		* @param mayInterruptIfRunning this value is ignored in the
722	<	* default implementation because tasks are not in general
722	>	* default implementation because tasks are not
723		* cancelled via interruption
724		*
725	<	* @return true if this task is now cancelled
725	>	* @return {@code true} if this task is now cancelled
726		*/
727		public boolean cancel(boolean mayInterruptIfRunning) {
728		setCompletion(CANCELLED);
729		return (status & COMPLETION_MASK) == CANCELLED;
730		}
731
732	+	public final boolean isDone() {
733	+	return status < 0;
734	+	}
735	+
736	+	public final boolean isCancelled() {
737	+	return (status & COMPLETION_MASK) == CANCELLED;
738	+	}
739	+
740		/**
741	<	* Returns true if this task threw an exception or was cancelled.
741	>	* Returns {@code true} if this task threw an exception or was cancelled.
742		*
743	<	* @return true if this task threw an exception or was cancelled
743	>	* @return {@code true} if this task threw an exception or was cancelled
744		*/
745		public final boolean isCompletedAbnormally() {
746		return (status & COMPLETION_MASK) < NORMAL;
747		}
748
749		/**
750	+	* Returns {@code true} if this task completed without throwing an
751	+	* exception and was not cancelled.
752	+	*
753	+	* @return {@code true} if this task completed without throwing an
754	+	* exception and was not cancelled
755	+	*/
756	+	public final boolean isCompletedNormally() {
757	+	return (status & COMPLETION_MASK) == NORMAL;
758	+	}
759	+
760	+	/**
761		* Returns the exception thrown by the base computation, or a
762	<	* CancellationException if cancelled, or null if none or if the
763	<	* method has not yet completed.
762	>	* {@code CancellationException} if cancelled, or {@code null} if
763	>	* none or if the method has not yet completed.
764		*
765	<	* @return the exception, or null if none
765	>	* @return the exception, or {@code null} if none
766		*/
767		public final Throwable getException() {
768		int s = status & COMPLETION_MASK;
769	<	if (s >= NORMAL)
770	<	return null;
771	<	if (s == CANCELLED)
726	<	return new CancellationException();
727	<	return exceptionMap.get(this);
769	>	return ((s >= NORMAL)    ? null :
770	>	(s == CANCELLED) ? new CancellationException() :
771	>	exceptionMap.get(this));
772		}
773
774		/**
#	Line 733 | Line 777 | public abstract class ForkJoinTask<V> im
777		* {@code join} and related operations. This method may be used
778		* to induce exceptions in asynchronous tasks, or to force
779		* completion of tasks that would not otherwise complete.  Its use
780	<	* in other situations is likely to be wrong.  This method is
780	>	* in other situations is discouraged.  This method is
781		* overridable, but overridden versions must invoke {@code super}
782		* implementation to maintain guarantees.
783		*
784	<	* @param ex the exception to throw. If this exception is
785	<	* not a RuntimeException or Error, the actual exception thrown
786	<	* will be a RuntimeException with cause ex.
784	>	* @param ex the exception to throw. If this exception is not a
785	>	* {@code RuntimeException} or {@code Error}, the actual exception
786	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
787		*/
788		public void completeExceptionally(Throwable ex) {
789		setDoneExceptionally((ex instanceof RuntimeException) ||
#	Line 753 | Line 797 | public abstract class ForkJoinTask<V> im
797		* operations. This method may be used to provide results for
798		* asynchronous tasks, or to provide alternative handling for
799		* tasks that would not otherwise complete normally. Its use in
800	<	* other situations is likely to be wrong. This method is
800	>	* other situations is discouraged. This method is
801		* overridable, but overridden versions must invoke {@code super}
802		* implementation to maintain guarantees.
803		*
#	Line 778 | Line 822 | public abstract class ForkJoinTask<V> im
822
823		public final V get(long timeout, TimeUnit unit)
824		throws InterruptedException, ExecutionException, TimeoutException {
825	+	long nanos = unit.toNanos(timeout);
826		ForkJoinWorkerThread w = getWorker();
827		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
828	<	awaitDone(w, unit.toNanos(timeout));
828	>	awaitDone(w, nanos);
829		return reportTimedFutureResult();
830		}
831
832		/**
833	<	* Possibly executes other tasks until this task is ready, then
834	<	* returns the result of the computation.  This method may be more
835	<	* efficient than {@code join}, but is only applicable when
836	<	* there are no potential dependencies between continuation of the
837	<	* current task and that of any other task that might be executed
838	<	* while helping. (This usually holds for pure divide-and-conquer
839	<	* tasks). This method may be invoked only from within
840	<	* ForkJoinTask computations (as may be determined using method
841	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
842	<	* result in exceptions or errors, possibly including
843	<	* ClassCastException.
833	>	* Possibly executes other tasks until this task {@link #isDone is
834	>	* done}, then returns the result of the computation.  This method
835	>	* may be more efficient than {@code join}, but is only applicable
836	>	* when there are no potential dependencies between continuation
837	>	* of the current task and that of any other task that might be
838	>	* executed while helping. (This usually holds for pure
839	>	* divide-and-conquer tasks).
840	>	*
841	>	* <p>This method may be invoked only from within {@code
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 {@code
845	>	* ClassCastException}.
846		*
847		* @return the computed result
848		*/
#	Line 807 | Line 854 | public abstract class ForkJoinTask<V> im
854		}
855
856		/**
857	<	* Possibly executes other tasks until this task is ready.  This
858	<	* method may be invoked only from within ForkJoinTask
859	<	* computations (as may be determined using method {@link
860	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
861	<	* in exceptions or errors, possibly including ClassCastException.
857	>	* Possibly executes other tasks until this task {@link #isDone is
858	>	* done}.  This method may be useful when processing collections
859	>	* of tasks when some have been cancelled or otherwise known to
860	>	* have aborted.
861	>	*
862	>	* <p>This method may be invoked only from within {@code
863	>	* ForkJoinTask} computations (as may be determined using method
864	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
865	>	* result in exceptions or errors, possibly including {@code
866	>	* ClassCastException}.
867		*/
868		public final void quietlyHelpJoin() {
869		if (status >= 0) {
#	Line 850 | Line 902 | public abstract class ForkJoinTask<V> im
902
903		/**
904		* Possibly executes tasks until the pool hosting the current task
905	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
906	<	* designs in which many tasks are forked, but none are explicitly
907	<	* joined, instead executing them until all are processed.
905	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
906	>	* be of use in designs in which many tasks are forked, but none
907	>	* are explicitly joined, instead executing them until all are
908	>	* processed.
909	>	*
910	>	* <p>This method may be invoked only from within {@code
911	>	* ForkJoinTask} computations (as may be determined using method
912	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
913	>	* result in exceptions or errors, possibly including {@code
914	>	* ClassCastException}.
915		*/
916		public static void helpQuiesce() {
917		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 865 | Line 924 | public abstract class ForkJoinTask<V> im
924		* this task, but only if reuse occurs when this task has either
925		* never been forked, or has been forked, then completed and all
926		* outstanding joins of this task have also completed. Effects
927	<	* under any other usage conditions are not guaranteed, and are
928	<	* almost surely wrong. This method may be useful when executing
927	>	* under any other usage conditions are not guaranteed.
928	>	* This method may be useful when executing
929		* pre-constructed trees of subtasks in loops.
930		*/
931		public void reinitialize() {
#	Line 879 | Line 938 | public abstract class ForkJoinTask<V> im
938		* Returns the pool hosting the current task execution, or null
939		* if this task is executing outside of any ForkJoinPool.
940		*
941	<	* @return the pool, or null if none
941	>	* @see #inForkJoinPool
942	>	* @return the pool, or {@code null} if none
943		*/
944		public static ForkJoinPool getPool() {
945		Thread t = Thread.currentThread();
#	Line 904 | Line 964 | public abstract class ForkJoinTask<V> im
964		* by the current thread, and has not commenced executing in
965		* another thread.  This method may be useful when arranging
966		* alternative local processing of tasks that could have been, but
967	<	* were not, stolen. This method may be invoked only from within
968	<	* ForkJoinTask computations (as may be determined using method
969	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
970	<	* result in exceptions or errors, possibly including
971	<	* ClassCastException.
967	>	* were not, stolen.
968	>	*
969	>	* <p>This method may be invoked only from within {@code
970	>	* ForkJoinTask} computations (as may be determined using method
971	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
972	>	* result in exceptions or errors, possibly including {@code
973	>	* ClassCastException}.
974		*
975	<	* @return true if unforked
975	>	* @return {@code true} if unforked
976		*/
977		public boolean tryUnfork() {
978		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 923 | Line 985 | public abstract class ForkJoinTask<V> im
985		* value may be useful for heuristic decisions about whether to
986		* fork other tasks.
987		*
988	+	* <p>This method may be invoked only from within {@code
989	+	* ForkJoinTask} computations (as may be determined using method
990	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
991	+	* result in exceptions or errors, possibly including {@code
992	+	* ClassCastException}.
993	+	*
994		* @return the number of tasks
995		*/
996		public static int getQueuedTaskCount() {
#	Line 940 | Line 1008 | public abstract class ForkJoinTask<V> im
1008		* tasks, and to process computations locally if this threshold is
1009		* exceeded.
1010		*
1011	+	* <p>This method may be invoked only from within {@code
1012	+	* ForkJoinTask} computations (as may be determined using method
1013	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1014	+	* result in exceptions or errors, possibly including {@code
1015	+	* ClassCastException}.
1016	+	*
1017		* @return the surplus number of tasks, which may be negative
1018		*/
1019		public static int getSurplusQueuedTaskCount() {
#	Line 950 | Line 1024 | public abstract class ForkJoinTask<V> im
1024		// Extension methods
1025
1026		/**
1027	<	* Returns the result that would be returned by {@code join},
1028	<	* even if this task completed abnormally, or null if this task is
1029	<	* not known to have been completed.  This method is designed to
1030	<	* aid debugging, as well as to support extensions. Its use in any
1031	<	* other context is discouraged.
1027	>	* Returns the result that would be returned by {@link #join}, even
1028	>	* if this task completed abnormally, or {@code null} if this task
1029	>	* is not known to have been completed.  This method is designed
1030	>	* to aid debugging, as well as to support extensions. Its use in
1031	>	* any other context is discouraged.
1032		*
1033	<	* @return the result, or null if not completed
1033	>	* @return the result, or {@code null} if not completed
1034		*/
1035		public abstract V getRawResult();
1036
#	Line 975 | Line 1049 | public abstract class ForkJoinTask<V> im
1049		* called otherwise. The return value controls whether this task
1050		* is considered to be done normally. It may return false in
1051		* asynchronous actions that require explicit invocations of
1052	<	* {@code complete} to become joinable. It may throw exceptions
1053	<	* to indicate abnormal exit.
1052	>	* {@link #complete} to become joinable. It may also throw an
1053	>	* (unchecked) exception to indicate abnormal exit.
1054		*
1055	<	* @return true if completed normally
982	<	* @throws Error or RuntimeException if encountered during computation
1055	>	* @return {@code true} if completed normally
1056		*/
1057		protected abstract boolean exec();
1058
1059		/**
1060	<	* Returns, but does not unschedule or execute, the task queued by
1061	<	* the current thread but not yet executed, if one is
1060	>	* Returns, but does not unschedule or execute, a task queued by
1061	>	* the current thread but not yet executed, if one is immediately
1062		* available. There is no guarantee that this task will actually
1063	<	* be polled or executed next.  This method is designed primarily
1064	<	* to support extensions, and is unlikely to be useful otherwise.
1065	<	* This method may be invoked only from within ForkJoinTask
1066	<	* computations (as may be determined using method {@link
1067	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
1068	<	* in exceptions or errors, possibly including ClassCastException.
1063	>	* be polled or executed next. Conversely, this method may return
1064	>	* null even if a task exists but cannot be accessed without
1065	>	* contention with other threads.  This method is designed
1066	>	* primarily to support extensions, and is unlikely to be useful
1067	>	* otherwise.
1068	>	*
1069	>	* <p>This method may be invoked only from within {@code
1070	>	* ForkJoinTask} computations (as may be determined using method
1071	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1072	>	* result in exceptions or errors, possibly including {@code
1073	>	* ClassCastException}.
1074		*
1075	<	* @return the next task, or null if none are available
1075	>	* @return the next task, or {@code null} if none are available
1076		*/
1077		protected static ForkJoinTask<?> peekNextLocalTask() {
1078		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1005 | Line 1083 | public abstract class ForkJoinTask<V> im
1083		* Unschedules and returns, without executing, the next task
1084		* queued by the current thread but not yet executed.  This method
1085		* is designed primarily to support extensions, and is unlikely to
1086	<	* be useful otherwise.  This method may be invoked only from
1009	<	* within ForkJoinTask computations (as may be determined using
1010	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1011	<	* contexts result in exceptions or errors, possibly including
1012	<	* ClassCastException.
1086	>	* be useful otherwise.
1087		*
1088	<	* @return the next task, or null if none are available
1088	>	* <p>This method may be invoked only from within {@code
1089	>	* ForkJoinTask} computations (as may be determined using method
1090	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1091	>	* result in exceptions or errors, possibly including {@code
1092	>	* ClassCastException}.
1093	>	*
1094	>	* @return the next task, or {@code null} if none are available
1095		*/
1096		protected static ForkJoinTask<?> pollNextLocalTask() {
1097		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1026 | Line 1106 | public abstract class ForkJoinTask<V> im
1106		* {@code null} result does not necessarily imply quiescence
1107		* of the pool this task is operating in.  This method is designed
1108		* primarily to support extensions, and is unlikely to be useful
1109	<	* otherwise.  This method may be invoked only from within
1110	<	* ForkJoinTask computations (as may be determined using method
1111	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1112	<	* result in exceptions or errors, possibly including
1113	<	* ClassCastException.
1109	>	* otherwise.
1110	>	*
1111	>	* <p>This method may be invoked only from within {@code
1112	>	* ForkJoinTask} computations (as may be determined using method
1113	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1114	>	* result in exceptions or errors, possibly including {@code
1115	>	* ClassCastException}.
1116		*
1117	<	* @return a task, or null if none are available
1117	>	* @return a task, or {@code null} if none are available
1118		*/
1119		protected static ForkJoinTask<?> pollTask() {
1120		return ((ForkJoinWorkerThread) Thread.currentThread())
1121		.pollTask();
1122		}
1123
1124	<	// adaptors
1124	>	/**
1125	>	* Adaptor for Runnables. This implements RunnableFuture
1126	>	* to be compliant with AbstractExecutorService constraints
1127	>	* when used in ForkJoinPool.
1128	>	*/
1129	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1130	>	implements RunnableFuture<T> {
1131	>	final Runnable runnable;
1132	>	final T resultOnCompletion;
1133	>	T result;
1134	>	AdaptedRunnable(Runnable runnable, T result) {
1135	>	if (runnable == null) throw new NullPointerException();
1136	>	this.runnable = runnable;
1137	>	this.resultOnCompletion = result;
1138	>	}
1139	>	public T getRawResult() { return result; }
1140	>	public void setRawResult(T v) { result = v; }
1141	>	public boolean exec() {
1142	>	runnable.run();
1143	>	result = resultOnCompletion;
1144	>	return true;
1145	>	}
1146	>	public void run() { invoke(); }
1147	>	private static final long serialVersionUID = 5232453952276885070L;
1148	>	}
1149	>
1150	>	/**
1151	>	* Adaptor for Callables
1152	>	*/
1153	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1154	>	implements RunnableFuture<T> {
1155	>	final Callable<? extends T> callable;
1156	>	T result;
1157	>	AdaptedCallable(Callable<? extends T> callable) {
1158	>	if (callable == null) throw new NullPointerException();
1159	>	this.callable = callable;
1160	>	}
1161	>	public T getRawResult() { return result; }
1162	>	public void setRawResult(T v) { result = v; }
1163	>	public boolean exec() {
1164	>	try {
1165	>	result = callable.call();
1166	>	return true;
1167	>	} catch (Error err) {
1168	>	throw err;
1169	>	} catch (RuntimeException rex) {
1170	>	throw rex;
1171	>	} catch (Exception ex) {
1172	>	throw new RuntimeException(ex);
1173	>	}
1174	>	}
1175	>	public void run() { invoke(); }
1176	>	private static final long serialVersionUID = 2838392045355241008L;
1177	>	}
1178
1179		/**
1180	<	* Returns a new ForkJoinTask that performs the {@code run}
1181	<	* method of the given Runnable as its action, and returns a null
1182	<	* result upon {@code join}.
1180	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1181	>	* method of the given {@code Runnable} as its action, and returns
1182	>	* a null result upon {@link #join}.
1183		*
1184		* @param runnable the runnable action
1185		* @return the task
1186		*/
1187	<	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1188	<	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1187	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1188	>	return new AdaptedRunnable<Void>(runnable, null);
1189		}
1190
1191		/**
1192	<	* Returns a new ForkJoinTask that performs the {@code run}
1193	<	* method of the given Runnable as its action, and returns the
1194	<	* given result upon {@code join}.
1192	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1193	>	* method of the given {@code Runnable} as its action, and returns
1194	>	* the given result upon {@link #join}.
1195		*
1196		* @param runnable the runnable action
1197		* @param result the result upon completion
1198		* @return the task
1199		*/
1200		public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1201	<	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1201	>	return new AdaptedRunnable<T>(runnable, result);
1202		}
1203
1204		/**
1205	<	* Returns a new ForkJoinTask that performs the {@code call}
1206	<	* method of the given Callable as its action, and returns its
1207	<	* result upon {@code join}, translating any checked
1208	<	* exceptions encountered into {@code RuntimeException}.
1205	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1206	>	* method of the given {@code Callable} as its action, and returns
1207	>	* its result upon {@link #join}, translating any checked exceptions
1208	>	* encountered into {@code RuntimeException}.
1209		*
1210		* @param callable the callable action
1211		* @return the task
1212		*/
1213	<	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1214	<	return new ForkJoinPool.AdaptedCallable<T>(callable);
1213	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1214	>	return new AdaptedCallable<T>(callable);
1215		}
1216
1217		// Serialization support
#	Line 1087 | Line 1222 | public abstract class ForkJoinTask<V> im
1222		* Save the state to a stream.
1223		*
1224		* @serialData the current run status and the exception thrown
1225	<	* during execution, or null if none
1225	>	* during execution, or {@code null} if none
1226		* @param s the stream
1227		*/
1228		private void writeObject(java.io.ObjectOutputStream s)

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