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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.9 by jsr166, Mon Jul 20 22:26:03 2009 UTC vs.
Revision 1.32 by dl, Mon Aug 3 13:01:15 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.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
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 72 | Line 77 | import java.lang.reflect.*;
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 ForkJoinTask class is not usually directly subclassed.
81		* Instead, you subclass one of the abstract classes that support a
82	<	* particular style of fork/join processing.  Normally, a concrete
82	>	* particular style of fork/join processing, typically {@link
83	>	* RecursiveAction} for computations that do not return results, or
84	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
85		* ForkJoinTask subclass declares fields comprising its parameters,
86		* established in a constructor, and then defines a {@code compute}
87		* method that somehow uses the control methods supplied by this base
88		* class. While these methods have {@code public} access (to allow
89	<	* instances of different task subclasses to call each others
89	>	* instances of different task subclasses to call each other's
90		* methods), some of them may only be called from within other
91	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
92	<	* exceptions or errors possibly including ClassCastException.
91	>	* ForkJoinTasks (as may be determined using method {@link
92	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
93	>	* result in exceptions or errors, possibly including
94	>	* ClassCastException.
95		*
96	<	* <p>Most base support methods are {@code final} because their
97	<	* implementations are intrinsically tied to the underlying
98	<	* lightweight task scheduling framework, and so cannot be overridden.
99	<	* Developers creating new basic styles of fork/join processing should
100	<	* minimally implement {@code protected} methods
101	<	* {@code exec}, {@code setRawResult}, and
102	<	* {@code getRawResult}, while also introducing an abstract
103	<	* computational method that can be implemented in its subclasses,
104	<	* possibly relying on other {@code protected} methods provided
96	<	* by this class.
96	>	* <p>Most base support methods are {@code final}, to prevent
97	>	* overriding of implementations that are intrinsically tied to the
98	>	* underlying lightweight task scheduling framework.  Developers
99	>	* creating new basic styles of fork/join processing should minimally
100	>	* implement {@code protected} methods {@link #exec}, {@link
101	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
102	>	* an abstract computational method that can be implemented in its
103	>	* subclasses, possibly relying on other {@code protected} methods
104	>	* provided by this class.
105		*
106		* <p>ForkJoinTasks should perform relatively small amounts of
107	<	* computations, otherwise splitting into smaller tasks. As a very
108	<	* rough rule of thumb, a task should perform more than 100 and less
109	<	* than 10000 basic computational steps. If tasks are too big, then
110	<	* parallelism cannot improve throughput. If too small, then memory
111	<	* and internal task maintenance overhead may overwhelm processing.
107	>	* computation. Large tasks should be split into smaller subtasks,
108	>	* usually via recursive decomposition. As a very rough rule of thumb,
109	>	* a task should perform more than 100 and less than 10000 basic
110	>	* computational steps. If tasks are too big, then parallelism cannot
111	>	* improve throughput. If too small, then memory and internal task
112	>	* maintenance overhead may overwhelm processing.
113		*
114	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
115	<	* to be used in extensions such as remote execution frameworks. It is
116	<	* in general sensible to serialize tasks only before or after, but
117	<	* not during execution. Serialization is not relied on during
118	<	* execution itself.
114	>	* <p>This class provides {@code adapt} methods for {@link
115	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
116	>	* may be of use when mixing execution of ForkJoinTasks with other
117	>	* kinds of tasks. When all tasks are of this form, consider using a
118	>	* pool in {@link ForkJoinPool#setAsyncMode}.
119	>	*
120	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
121	>	* used in extensions such as remote execution frameworks. It is
122	>	* sensible to serialize tasks only before or after, but not during,
123	>	* execution. Serialization is not relied on during execution itself.
124	>	*
125	>	* @since 1.7
126	>	* @author Doug Lea
127		*/
128		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
129
#	Line 141 | Line 158 | public abstract class ForkJoinTask<V> im
158		/**
159		* Table of exceptions thrown by tasks, to enable reporting by
160		* callers. Because exceptions are rare, we don't directly keep
161	<	* them with task objects, but instead us a weak ref table.  Note
161	>	* them with task objects, but instead use a weak ref table.  Note
162		* that cancellation exceptions don't appear in the table, but are
163		* instead recorded as status values.
164	<	* Todo: Use ConcurrentReferenceHashMap
164	>	* TODO: Use ConcurrentReferenceHashMap
165		*/
166		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
167		Collections.synchronizedMap
#	Line 153 | Line 170 | public abstract class ForkJoinTask<V> im
170		// within-package utilities
171
172		/**
173	<	* Get current worker thread, or null if not a worker thread
173	>	* Gets current worker thread, or null if not a worker thread.
174		*/
175		static ForkJoinWorkerThread getWorker() {
176		Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread)?
178	<	(ForkJoinWorkerThread)t : null);
177	>	return ((t instanceof ForkJoinWorkerThread) ?
178	>	(ForkJoinWorkerThread) t : null);
179		}
180
181		final boolean casStatus(int cmp, int val) {
182	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
182	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183		}
184
185		/**
#	Line 170 | Line 187 | public abstract class ForkJoinTask<V> im
187		*/
188		static void rethrowException(Throwable ex) {
189		if (ex != null)
190	<	_unsafe.throwException(ex);
190	>	UNSAFE.throwException(ex);
191		}
192
193		// Setting completion status
194
195		/**
196	<	* Mark completion and wake up threads waiting to join this task.
196	>	* Marks completion and wakes up threads waiting to join this task.
197	>	*
198		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
199		*/
200		final void setCompletion(int completion) {
201		ForkJoinPool pool = getPool();
202		if (pool != null) {
203		int s; // Clear signal bits while setting completion status
204	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
204	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
205
206		if ((s & SIGNAL_MASK) != 0) {
207		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208		pool.updateRunningCount(s);
209	<	synchronized(this) { notifyAll(); }
209	>	synchronized (this) { notifyAll(); }
210		}
211		}
212		else
#	Line 201 | Line 219 | public abstract class ForkJoinTask<V> im
219		*/
220		private void externallySetCompletion(int completion) {
221		int s;
222	<	do;while ((s = status) >= 0 &&
223	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	<	synchronized(this) { notifyAll(); }
222	>	do {} while ((s = status) >= 0 &&
223	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	>	synchronized (this) { notifyAll(); }
225		}
226
227		/**
228	<	* Sets status to indicate normal completion
228	>	* Sets status to indicate normal completion.
229		*/
230		final void setNormalCompletion() {
231		// Try typical fast case -- single CAS, no signal, not already done.
232		// Manually expand casStatus to improve chances of inlining it
233	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
233	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234		setCompletion(NORMAL);
235		}
236
237		// internal waiting and notification
238
239		/**
240	<	* Performs the actual monitor wait for awaitDone
240	>	* Performs the actual monitor wait for awaitDone.
241		*/
242		private void doAwaitDone() {
243		// Minimize lock bias and in/de-flation effects by maximizing
244		// chances of waiting inside sync
245		try {
246		while (status >= 0)
247	<	synchronized(this) { if (status >= 0) wait(); }
247	>	synchronized (this) { if (status >= 0) wait(); }
248		} catch (InterruptedException ie) {
249		onInterruptedWait();
250		}
251		}
252
253		/**
254	<	* Performs the actual monitor wait for awaitDone
254	>	* Performs the actual timed monitor wait for awaitDone.
255		*/
256		private void doAwaitDone(long startTime, long nanos) {
257	<	synchronized(this) {
257	>	synchronized (this) {
258		try {
259		while (status >= 0) {
260	<	long nt = nanos - System.nanoTime() - startTime;
260	>	long nt = nanos - (System.nanoTime() - startTime);
261		if (nt <= 0)
262		break;
263	<	wait(nt / 1000000, (int)(nt % 1000000));
263	>	wait(nt / 1000000, (int) (nt % 1000000));
264		}
265		} catch (InterruptedException ie) {
266		onInterruptedWait();
#	Line 255 | Line 273 | public abstract class ForkJoinTask<V> im
273		/**
274		* Sets status to indicate there is joiner, then waits for join,
275		* surrounded with pool notifications.
276	+	*
277		* @return status upon exit
278		*/
279	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
280	<	ForkJoinPool pool = w == null? null : w.pool;
279	>	private int awaitDone(ForkJoinWorkerThread w,
280	>	boolean maintainParallelism) {
281	>	ForkJoinPool pool = (w == null) ? null : w.pool;
282		int s;
283		while ((s = status) >= 0) {
284	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
284	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285		if (pool == null || !pool.preJoin(this, maintainParallelism))
286		doAwaitDone();
287		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 294 | public abstract class ForkJoinTask<V> im
294
295		/**
296		* Timed version of awaitDone
297	+	*
298		* @return status upon exit
299		*/
300		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = w == null? null : w.pool;
301	>	ForkJoinPool pool = (w == null) ? null : w.pool;
302		int s;
303		while ((s = status) >= 0) {
304	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
304	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
305		long startTime = System.nanoTime();
306		if (pool == null || !pool.preJoin(this, false))
307		doAwaitDone(startTime, nanos);
#	Line 297 | Line 318 | public abstract class ForkJoinTask<V> im
318		}
319
320		/**
321	<	* Notify pool that thread is unblocked. Called by signalled
321	>	* Notifies pool that thread is unblocked. Called by signalled
322		* threads when woken by non-FJ threads (which is atypical).
323		*/
324		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
325		int s;
326	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
326	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
327		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
328		pool.updateRunningCount(s);
329		}
330
331		/**
332	<	* Notify pool to adjust counts on cancelled or timed out wait
332	>	* Notifies pool to adjust counts on cancelled or timed out wait.
333		*/
334		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
335		if (pool != null) {
#	Line 323 | Line 344 | public abstract class ForkJoinTask<V> im
344		}
345
346		/**
347	<	* Handle interruptions during waits.
347	>	* Handles interruptions during waits.
348		*/
349		private void onInterruptedWait() {
350		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Throws the exception associated with status s;
366	>	* Throws the exception associated with status s.
367	>	*
368		* @throws the exception
369		*/
370		private void reportException(int s) {
#	Line 355 | Line 377 | public abstract class ForkJoinTask<V> im
377		}
378
379		/**
380	<	* Returns result or throws exception using j.u.c.Future conventions
381	<	* Only call when isDone known to be true.
380	>	* Returns result or throws exception using j.u.c.Future conventions.
381	>	* Only call when {@code isDone} known to be true.
382		*/
383		private V reportFutureResult()
384		throws ExecutionException, InterruptedException {
#	Line 375 | Line 397 | public abstract class ForkJoinTask<V> im
397
398		/**
399		* Returns result or throws exception using j.u.c.Future conventions
400	<	* with timeouts
400	>	* with timeouts.
401		*/
402		private V reportTimedFutureResult()
403		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 418 | public abstract class ForkJoinTask<V> im
418
419		/**
420		* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling
421	>	* encountered. Caller should normally check status before calling.
422	>	*
423		* @return true if completed normally
424		*/
425		private boolean tryExec() {
#	Line 414 | Line 437 | public abstract class ForkJoinTask<V> im
437
438		/**
439		* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete
440	>	* base computation unless already complete.
441		*/
442		final void quietlyExec() {
443		if (status >= 0) {
444		try {
445		if (!exec())
446		return;
447	<	} catch(Throwable rex) {
447	>	} catch (Throwable rex) {
448		setDoneExceptionally(rex);
449		return;
450		}
#	Line 430 | Line 453 | public abstract class ForkJoinTask<V> im
453		}
454
455		/**
456	<	* Calls exec, recording but not rethrowing exception
457	<	* Caller should normally check status before calling
456	>	* Calls exec(), recording but not rethrowing exception.
457	>	* Caller should normally check status before calling.
458	>	*
459		* @return true if completed normally
460		*/
461		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 471 | public abstract class ForkJoinTask<V> im
471		}
472
473		/**
474	<	* Cancel, ignoring any exceptions it throws
474	>	* Cancels, ignoring any exceptions it throws.
475		*/
476		final void cancelIgnoringExceptions() {
477		try {
478		cancel(false);
479	<	} catch(Throwable ignore) {
479	>	} catch (Throwable ignore) {
480		}
481		}
482
#	Line 464 | Line 488 | public abstract class ForkJoinTask<V> im
488		ForkJoinTask<?> t;
489		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
490		t.quietlyExec();
491	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
491	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
492		}
493
494		// public methods
#	Line 472 | Line 496 | public abstract class ForkJoinTask<V> im
496		/**
497		* Arranges to asynchronously execute this task.  While it is not
498		* necessarily enforced, it is a usage error to fork a task more
499	<	* than once unless it has completed and been reinitialized.  This
500	<	* method may be invoked only from within ForkJoinTask
501	<	* computations. Attempts to invoke in other contexts result in
502	<	* exceptions or errors possibly including ClassCastException.
499	>	* than once unless it has completed and been reinitialized.
500	>	*
501	>	* <p>This method may be invoked only from within {@code
502	>	* ForkJoinTask} computations (as may be determined using method
503	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
504	>	* result in exceptions or errors, possibly including {@code
505	>	* ClassCastException}.
506	>	*
507	>	* @return {@code this}, to simplify usage
508		*/
509	<	public final void fork() {
510	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
509	>	public final ForkJoinTask<V> fork() {
510	>	((ForkJoinWorkerThread) Thread.currentThread())
511	>	.pushTask(this);
512	>	return this;
513		}
514
515		/**
516		* Returns the result of the computation when it is ready.
517	<	* This method differs from {@code get} in that abnormal
518	<	* completion results in RuntimeExceptions or Errors, not
519	<	* ExecutionExceptions.
517	>	* This method differs from {@link #get()} in that
518	>	* abnormal completion results in {@code RuntimeException} or
519	>	* {@code Error}, not {@code ExecutionException}.
520		*
521		* @return the computed result
522		*/
#	Line 499 | Line 530 | public abstract class ForkJoinTask<V> im
530		/**
531		* Commences performing this task, awaits its completion if
532		* necessary, and return its result.
533	+	*
534		* @throws Throwable (a RuntimeException, Error, or unchecked
535	<	* exception) if the underlying computation did so.
535	>	* exception) if the underlying computation did so
536		* @return the computed result
537		*/
538		public final V invoke() {
#	Line 511 | Line 543 | public abstract class ForkJoinTask<V> im
543		}
544
545		/**
546	<	* Forks both tasks, returning when {@code isDone} holds for
547	<	* both of them or an exception is encountered. This method may be
548	<	* invoked only from within ForkJoinTask computations. Attempts to
549	<	* invoke in other contexts result in exceptions or errors
550	<	* possibly including ClassCastException.
551	<	* @param t1 one task
552	<	* @param t2 the other task
553	<	* @throws NullPointerException if t1 or t2 are null
554	<	* @throws RuntimeException or Error if either task did so.
546	>	* Forks the given tasks, returning when {@code isDone} holds
547	>	* for each task or an exception is encountered.
548	>	*
549	>	* <p>This method may be invoked only from within {@code
550	>	* ForkJoinTask} computations (as may be determined using method
551	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
552	>	* result in exceptions or errors, possibly including {@code
553	>	* ClassCastException}.
554	>	*
555	>	* @param t1 the first task
556	>	* @param t2 the second task
557	>	* @throws NullPointerException if any task is null
558	>	* @throws RuntimeException or Error if a task did so
559		*/
560	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
560	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
561		t2.fork();
562		t1.invoke();
563		t2.join();
564		}
565
566		/**
567	<	* Forks the given tasks, returning when {@code isDone} holds
568	<	* for all of them. If any task encounters an exception, others
569	<	* may be cancelled.  This method may be invoked only from within
570	<	* ForkJoinTask computations. Attempts to invoke in other contexts
571	<	* result in exceptions or errors possibly including ClassCastException.
572	<	* @param tasks the array of tasks
573	<	* @throws NullPointerException if tasks or any element are null.
574	<	* @throws RuntimeException or Error if any task did so.
567	>	* Forks the given tasks, returning when {@code isDone} holds for
568	>	* each task or an exception is encountered. If any task
569	>	* encounters an exception, others may be, but are not guaranteed
570	>	* to be, cancelled.
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 tasks the tasks
579	>	* @throws NullPointerException if tasks or any element are null
580	>	* @throws RuntimeException or Error if any task did so
581		*/
582		public static void invokeAll(ForkJoinTask<?>... tasks) {
583		Throwable ex = null;
#	Line 571 | Line 613 | public abstract class ForkJoinTask<V> im
613		}
614
615		/**
616	<	* Forks all tasks in the collection, returning when
617	<	* {@code isDone} holds for all of them. If any task
618	<	* encounters an exception, others may be cancelled.  This method
619	<	* may be invoked only from within ForkJoinTask
620	<	* computations. Attempts to invoke in other contexts result in
621	<	* exceptions or errors possibly including ClassCastException.
616	>	* Forks all tasks in the specified collection, returning when
617	>	* {@code isDone} holds for each task or an exception is
618	>	* encountered.  If any task encounters an exception, others may
619	>	* be, but are not guaranteed to be, cancelled. The behavior of
620	>	* this operation is undefined if the specified collection is
621	>	* modified while the operation is in progress.
622	>	*
623	>	* <p>This method may be invoked only from within {@code
624	>	* ForkJoinTask} computations (as may be determined using method
625	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
626	>	* result in exceptions or errors, possibly including {@code
627	>	* ClassCastException}.
628	>	*
629		* @param tasks the collection of tasks
630	<	* @throws NullPointerException if tasks or any element are null.
631	<	* @throws RuntimeException or Error if any task did so.
632	<	*/
633	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
634	<	if (!(tasks instanceof List)) {
635	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
636	<	return;
630	>	* @return the tasks argument, to simplify usage
631	>	* @throws NullPointerException if tasks or any element are null
632	>	* @throws RuntimeException or Error if any task did so
633	>	*/
634	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
635	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
636	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
637	>	return tasks;
638		}
639	+	@SuppressWarnings("unchecked")
640		List<? extends ForkJoinTask<?>> ts =
641	<	(List<? extends ForkJoinTask<?>>)tasks;
641	>	(List<? extends ForkJoinTask<?>>) tasks;
642		Throwable ex = null;
643		int last = ts.size() - 1;
644		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 669 | public abstract class ForkJoinTask<V> im
669		}
670		if (ex != null)
671		rethrowException(ex);
672	+	return tasks;
673		}
674
675		/**
676	<	* Returns true if the computation performed by this task has
677	<	* completed (or has been cancelled).
678	<	* @return true if this computation has completed
676	>	* Returns {@code true} if the computation performed by this task
677	>	* has completed (or has been cancelled).
678	>	*
679	>	* @return {@code true} if this computation has completed
680		*/
681		public final boolean isDone() {
682		return status < 0;
683		}
684
685		/**
686	<	* Returns true if this task was cancelled.
687	<	* @return true if this task was cancelled
686	>	* Returns {@code true} if this task was cancelled.
687	>	*
688	>	* @return {@code true} if this task was cancelled
689		*/
690		public final boolean isCancelled() {
691		return (status & COMPLETION_MASK) == CANCELLED;
#	Line 640 | Line 694 | public abstract class ForkJoinTask<V> im
694		/**
695		* Asserts that the results of this task's computation will not be
696		* used. If a cancellation occurs before attempting to execute this
697	<	* task, then execution will be suppressed, {@code isCancelled}
698	<	* will report true, and {@code join} will result in a
697	>	* task, execution will be suppressed, {@link #isCancelled}
698	>	* will report true, and {@link #join} will result in a
699		* {@code CancellationException} being thrown. Otherwise, when
700		* cancellation races with completion, there are no guarantees
701	<	* about whether {@code isCancelled} will report true, whether
702	<	* {@code join} will return normally or via an exception, or
703	<	* whether these behaviors will remain consistent upon repeated
701	>	* about whether {@code isCancelled} will report {@code true},
702	>	* whether {@code join} will return normally or via an exception,
703	>	* or whether these behaviors will remain consistent upon repeated
704		* invocation.
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 cancel method itself must not throw exceptions.
708	>	* the {@code cancel} method itself must not throw exceptions.
709		*
710	<	* <p> This method is designed to be invoked by <em>other</em>
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 {@code completeExceptionally}.
713	>	* invoke {@link #completeExceptionally}.
714		*
715		* @param mayInterruptIfRunning this value is ignored in the
716		* default implementation because tasks are not in general
717	<	* cancelled via interruption.
717	>	* cancelled via interruption
718		*
719	<	* @return true if this task is now cancelled
719	>	* @return {@code true} if this task is now cancelled
720		*/
721		public boolean cancel(boolean mayInterruptIfRunning) {
722		setCompletion(CANCELLED);
#	Line 670 | Line 724 | public abstract class ForkJoinTask<V> im
724		}
725
726		/**
727	<	* Returns true if this task threw an exception or was cancelled
728	<	* @return true if this task threw an exception or was cancelled
727	>	* Returns {@code true} if this task threw an exception or was cancelled.
728	>	*
729	>	* @return {@code true} if this task threw an exception or was cancelled
730		*/
731		public final boolean isCompletedAbnormally() {
732		return (status & COMPLETION_MASK) < NORMAL;
#	Line 679 | Line 734 | public abstract class ForkJoinTask<V> im
734
735		/**
736		* Returns the exception thrown by the base computation, or a
737	<	* CancellationException if cancelled, or null if none or if the
738	<	* method has not yet completed.
739	<	* @return the exception, or null if none
737	>	* {@code CancellationException} if cancelled, or {@code null} if
738	>	* none or if the method has not yet completed.
739	>	*
740	>	* @return the exception, or {@code null} if none
741		*/
742		public final Throwable getException() {
743		int s = status & COMPLETION_MASK;
#	Line 698 | Line 754 | public abstract class ForkJoinTask<V> im
754		* {@code join} and related operations. This method may be used
755		* to induce exceptions in asynchronous tasks, or to force
756		* completion of tasks that would not otherwise complete.  Its use
757	<	* in other situations is likely to be wrong.  This method is
757	>	* in other situations is discouraged.  This method is
758		* overridable, but overridden versions must invoke {@code super}
759		* implementation to maintain guarantees.
760		*
#	Line 708 | Line 764 | public abstract class ForkJoinTask<V> im
764		*/
765		public void completeExceptionally(Throwable ex) {
766		setDoneExceptionally((ex instanceof RuntimeException) ||
767	<	(ex instanceof Error)? ex :
767	>	(ex instanceof Error) ? ex :
768		new RuntimeException(ex));
769		}
770
#	Line 718 | Line 774 | public abstract class ForkJoinTask<V> im
774		* operations. This method may be used to provide results for
775		* asynchronous tasks, or to provide alternative handling for
776		* tasks that would not otherwise complete normally. Its use in
777	<	* other situations is likely to be wrong. This method is
777	>	* other situations is discouraged. This method is
778		* overridable, but overridden versions must invoke {@code super}
779		* implementation to maintain guarantees.
780		*
781	<	* @param value the result value for this task.
781	>	* @param value the result value for this task
782		*/
783		public void complete(V value) {
784		try {
785		setRawResult(value);
786	<	} catch(Throwable rex) {
786	>	} catch (Throwable rex) {
787		setDoneExceptionally(rex);
788		return;
789		}
#	Line 743 | Line 799 | public abstract class ForkJoinTask<V> im
799
800		public final V get(long timeout, TimeUnit unit)
801		throws InterruptedException, ExecutionException, TimeoutException {
802	+	long nanos = unit.toNanos(timeout);
803		ForkJoinWorkerThread w = getWorker();
804		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
805	<	awaitDone(w, unit.toNanos(timeout));
805	>	awaitDone(w, nanos);
806		return reportTimedFutureResult();
807		}
808
#	Line 756 | Line 813 | public abstract class ForkJoinTask<V> im
813		* there are no potential dependencies between continuation of the
814		* current task and that of any other task that might be executed
815		* while helping. (This usually holds for pure divide-and-conquer
816	<	* tasks). This method may be invoked only from within
817	<	* ForkJoinTask computations. Attempts to invoke in other contexts
818	<	* result in exceptions or errors possibly including ClassCastException.
816	>	* tasks).
817	>	*
818	>	* <p>This method may be invoked only from within {@code
819	>	* ForkJoinTask} computations (as may be determined using method
820	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
821	>	* result in exceptions or errors, possibly including {@code
822	>	* ClassCastException}.
823	>	*
824		* @return the computed result
825		*/
826		public final V helpJoin() {
827	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
827	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
828		if (status < 0 || !w.unpushTask(this) || !tryExec())
829		reportException(busyJoin(w));
830		return getRawResult();
#	Line 770 | Line 832 | public abstract class ForkJoinTask<V> im
832
833		/**
834		* Possibly executes other tasks until this task is ready.  This
835	<	* method may be invoked only from within ForkJoinTask
836	<	* computations. Attempts to invoke in other contexts result in
837	<	* exceptions or errors possibly including ClassCastException.
835	>	* method may be useful when processing collections of tasks when
836	>	* some have been cancelled or otherwise known to have aborted.
837	>	*
838	>	* <p>This method may be invoked only from within {@code
839	>	* ForkJoinTask} computations (as may be determined using method
840	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
841	>	* result in exceptions or errors, possibly including {@code
842	>	* ClassCastException}.
843		*/
844		public final void quietlyHelpJoin() {
845		if (status >= 0) {
846		ForkJoinWorkerThread w =
847	<	(ForkJoinWorkerThread)(Thread.currentThread());
847	>	(ForkJoinWorkerThread) Thread.currentThread();
848		if (!w.unpushTask(this) || !tryQuietlyInvoke())
849		busyJoin(w);
850		}
#	Line 814 | Line 881 | public abstract class ForkJoinTask<V> im
881		* {@link ForkJoinPool#isQuiescent}. This method may be of use in
882		* designs in which many tasks are forked, but none are explicitly
883		* joined, instead executing them until all are processed.
884	+	*
885	+	* <p>This method may be invoked only from within {@code
886	+	* ForkJoinTask} computations (as may be determined using method
887	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
888	+	* result in exceptions or errors, possibly including {@code
889	+	* ClassCastException}.
890		*/
891		public static void helpQuiesce() {
892	<	((ForkJoinWorkerThread)(Thread.currentThread())).
893	<	helpQuiescePool();
892	>	((ForkJoinWorkerThread) Thread.currentThread())
893	>	.helpQuiescePool();
894		}
895
896		/**
#	Line 826 | Line 899 | public abstract class ForkJoinTask<V> im
899		* this task, but only if reuse occurs when this task has either
900		* never been forked, or has been forked, then completed and all
901		* outstanding joins of this task have also completed. Effects
902	<	* under any other usage conditions are not guaranteed, and are
903	<	* almost surely wrong. This method may be useful when executing
902	>	* under any other usage conditions are not guaranteed.
903	>	* This method may be useful when executing
904		* pre-constructed trees of subtasks in loops.
905		*/
906		public void reinitialize() {
#	Line 838 | Line 911 | public abstract class ForkJoinTask<V> im
911
912		/**
913		* Returns the pool hosting the current task execution, or null
914	<	* if this task is executing outside of any pool.
915	<	* @return the pool, or null if none.
914	>	* if this task is executing outside of any ForkJoinPool.
915	>	*
916	>	* @see #inForkJoinPool
917	>	* @return the pool, or {@code null} if none
918		*/
919		public static ForkJoinPool getPool() {
920		Thread t = Thread.currentThread();
921	<	return ((t instanceof ForkJoinWorkerThread)?
922	<	((ForkJoinWorkerThread)t).pool : null);
921	>	return (t instanceof ForkJoinWorkerThread) ?
922	>	((ForkJoinWorkerThread) t).pool : null;
923	>	}
924	>
925	>	/**
926	>	* Returns {@code true} if the current thread is executing as a
927	>	* ForkJoinPool computation.
928	>	*
929	>	* @return {@code true} if the current thread is executing as a
930	>	* ForkJoinPool computation, or false otherwise
931	>	*/
932	>	public static boolean inForkJoinPool() {
933	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
934		}
935
936		/**
#	Line 853 | Line 939 | public abstract class ForkJoinTask<V> im
939		* by the current thread, and has not commenced executing in
940		* another thread.  This method may be useful when arranging
941		* alternative local processing of tasks that could have been, but
942	<	* were not, stolen. This method may be invoked only from within
943	<	* ForkJoinTask computations. Attempts to invoke in other contexts
944	<	* result in exceptions or errors possibly including ClassCastException.
945	<	* @return true if unforked
942	>	* were not, stolen.
943	>	*
944	>	* <p>This method may be invoked only from within {@code
945	>	* ForkJoinTask} computations (as may be determined using method
946	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
947	>	* result in exceptions or errors, possibly including {@code
948	>	* ClassCastException}.
949	>	*
950	>	* @return {@code true} if unforked
951		*/
952		public boolean tryUnfork() {
953	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
953	>	return ((ForkJoinWorkerThread) Thread.currentThread())
954	>	.unpushTask(this);
955		}
956
957		/**
#	Line 867 | Line 959 | public abstract class ForkJoinTask<V> im
959		* forked by the current worker thread but not yet executed. This
960		* value may be useful for heuristic decisions about whether to
961		* fork other tasks.
962	+	*
963	+	* <p>This method may be invoked only from within {@code
964	+	* ForkJoinTask} computations (as may be determined using method
965	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
966	+	* result in exceptions or errors, possibly including {@code
967	+	* ClassCastException}.
968	+	*
969		* @return the number of tasks
970		*/
971		public static int getQueuedTaskCount() {
972	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
973	<	getQueueSize();
972	>	return ((ForkJoinWorkerThread) Thread.currentThread())
973	>	.getQueueSize();
974		}
975
976		/**
977	<	* Returns a estimate of how many more locally queued tasks are
977	>	* Returns an estimate of how many more locally queued tasks are
978		* held by the current worker thread than there are other worker
979		* threads that might steal them.  This value may be useful for
980		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 982 | public abstract class ForkJoinTask<V> im
982		* aim to maintain a small constant surplus (for example, 3) of
983		* tasks, and to process computations locally if this threshold is
984		* exceeded.
985	+	*
986	+	* <p>This method may be invoked only from within {@code
987	+	* ForkJoinTask} computations (as may be determined using method
988	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
989	+	* result in exceptions or errors, possibly including {@code
990	+	* ClassCastException}.
991	+	*
992		* @return the surplus number of tasks, which may be negative
993		*/
994		public static int getSurplusQueuedTaskCount() {
995	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
995	>	return ((ForkJoinWorkerThread) Thread.currentThread())
996		.getEstimatedSurplusTaskCount();
997		}
998
999		// Extension methods
1000
1001		/**
1002	<	* Returns the result that would be returned by {@code join},
1003	<	* even if this task completed abnormally, or null if this task is
1004	<	* not known to have been completed.  This method is designed to
1005	<	* aid debugging, as well as to support extensions. Its use in any
1006	<	* other context is discouraged.
1002	>	* Returns the result that would be returned by {@link #join}, even
1003	>	* if this task completed abnormally, or {@code null} if this task
1004	>	* is not known to have been completed.  This method is designed
1005	>	* to aid debugging, as well as to support extensions. Its use in
1006	>	* any other context is discouraged.
1007		*
1008	<	* @return the result, or null if not completed.
1008	>	* @return the result, or {@code null} if not completed
1009		*/
1010		public abstract V getRawResult();
1011
#	Line 918 | Line 1024 | public abstract class ForkJoinTask<V> im
1024		* called otherwise. The return value controls whether this task
1025		* is considered to be done normally. It may return false in
1026		* asynchronous actions that require explicit invocations of
1027	<	* {@code complete} to become joinable. It may throw exceptions
1027	>	* {@link #complete} to become joinable. It may throw exceptions
1028		* to indicate abnormal exit.
1029	<	* @return true if completed normally
1029	>	*
1030	>	* @return {@code true} if completed normally
1031		* @throws Error or RuntimeException if encountered during computation
1032		*/
1033		protected abstract boolean exec();
1034
1035		/**
1036	<	* Returns, but does not unschedule or execute, the task queued by
1037	<	* the current thread but not yet executed, if one is
1036	>	* Returns, but does not unschedule or execute, a task queued by
1037	>	* the current thread but not yet executed, if one is immediately
1038		* available. There is no guarantee that this task will actually
1039	<	* be polled or executed next.  This method is designed primarily
1040	<	* to support extensions, and is unlikely to be useful otherwise.
1041	<	* This method may be invoked only from within ForkJoinTask
1042	<	* computations. Attempts to invoke in other contexts result in
1043	<	* exceptions or errors possibly including ClassCastException.
1039	>	* be polled or executed next. Conversely, this method may return
1040	>	* null even if a task exists but cannot be accessed without
1041	>	* contention with other threads.  This method is designed
1042	>	* primarily to support extensions, and is unlikely to be useful
1043	>	* otherwise.
1044	>	*
1045	>	* <p>This method may be invoked only from within {@code
1046	>	* ForkJoinTask} computations (as may be determined using method
1047	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1048	>	* result in exceptions or errors, possibly including {@code
1049	>	* ClassCastException}.
1050		*
1051	<	* @return the next task, or null if none are available
1051	>	* @return the next task, or {@code null} if none are available
1052		*/
1053		protected static ForkJoinTask<?> peekNextLocalTask() {
1054	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
1054	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1055	>	.peekTask();
1056		}
1057
1058		/**
1059		* Unschedules and returns, without executing, the next task
1060		* queued by the current thread but not yet executed.  This method
1061		* is designed primarily to support extensions, and is unlikely to
1062	<	* be useful otherwise.  This method may be invoked only from
1063	<	* within ForkJoinTask computations. Attempts to invoke in other
1064	<	* contexts result in exceptions or errors possibly including
1065	<	* ClassCastException.
1062	>	* be useful otherwise.
1063	>	*
1064	>	* <p>This method may be invoked only from within {@code
1065	>	* ForkJoinTask} computations (as may be determined using method
1066	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1067	>	* result in exceptions or errors, possibly including {@code
1068	>	* ClassCastException}.
1069		*
1070	<	* @return the next task, or null if none are available
1070	>	* @return the next task, or {@code null} if none are available
1071		*/
1072		protected static ForkJoinTask<?> pollNextLocalTask() {
1073	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1073	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1074	>	.pollLocalTask();
1075		}
1076
1077		/**
#	Line 964 | Line 1082 | public abstract class ForkJoinTask<V> im
1082		* {@code null} result does not necessarily imply quiescence
1083		* of the pool this task is operating in.  This method is designed
1084		* primarily to support extensions, and is unlikely to be useful
1085	<	* otherwise.  This method may be invoked only from within
968	<	* ForkJoinTask computations. Attempts to invoke in other contexts
969	<	* result in exceptions or errors possibly including
970	<	* ClassCastException.
1085	>	* otherwise.
1086		*
1087	<	* @return a task, or null if none are available
1087	>	* <p>This method may be invoked only from within {@code
1088	>	* ForkJoinTask} computations (as may be determined using method
1089	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1090	>	* result in exceptions or errors, possibly including {@code
1091	>	* ClassCastException}.
1092	>	*
1093	>	* @return a task, or {@code null} if none are available
1094		*/
1095		protected static ForkJoinTask<?> pollTask() {
1096	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1097	<	pollTask();
1096	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1097	>	.pollTask();
1098	>	}
1099	>
1100	>	/**
1101	>	* Adaptor for Runnables. This implements RunnableFuture
1102	>	* to be compliant with AbstractExecutorService constraints
1103	>	* when used in ForkJoinPool.
1104	>	*/
1105	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1106	>	implements RunnableFuture<T> {
1107	>	final Runnable runnable;
1108	>	final T resultOnCompletion;
1109	>	T result;
1110	>	AdaptedRunnable(Runnable runnable, T result) {
1111	>	if (runnable == null) throw new NullPointerException();
1112	>	this.runnable = runnable;
1113	>	this.resultOnCompletion = result;
1114	>	}
1115	>	public T getRawResult() { return result; }
1116	>	public void setRawResult(T v) { result = v; }
1117	>	public boolean exec() {
1118	>	runnable.run();
1119	>	result = resultOnCompletion;
1120	>	return true;
1121	>	}
1122	>	public void run() { invoke(); }
1123	>	private static final long serialVersionUID = 5232453952276885070L;
1124	>	}
1125	>
1126	>	/**
1127	>	* Adaptor for Callables
1128	>	*/
1129	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1130	>	implements RunnableFuture<T> {
1131	>	final Callable<? extends T> callable;
1132	>	T result;
1133	>	AdaptedCallable(Callable<? extends T> callable) {
1134	>	if (callable == null) throw new NullPointerException();
1135	>	this.callable = callable;
1136	>	}
1137	>	public T getRawResult() { return result; }
1138	>	public void setRawResult(T v) { result = v; }
1139	>	public boolean exec() {
1140	>	try {
1141	>	result = callable.call();
1142	>	return true;
1143	>	} catch (Error err) {
1144	>	throw err;
1145	>	} catch (RuntimeException rex) {
1146	>	throw rex;
1147	>	} catch (Exception ex) {
1148	>	throw new RuntimeException(ex);
1149	>	}
1150	>	}
1151	>	public void run() { invoke(); }
1152	>	private static final long serialVersionUID = 2838392045355241008L;
1153	>	}
1154	>
1155	>	/**
1156	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1157	>	* method of the given {@code Runnable} as its action, and returns
1158	>	* a null result upon {@link #join}.
1159	>	*
1160	>	* @param runnable the runnable action
1161	>	* @return the task
1162	>	*/
1163	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1164	>	return new AdaptedRunnable<Void>(runnable, null);
1165	>	}
1166	>
1167	>	/**
1168	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1169	>	* method of the given {@code Runnable} as its action, and returns
1170	>	* the given result upon {@link #join}.
1171	>	*
1172	>	* @param runnable the runnable action
1173	>	* @param result the result upon completion
1174	>	* @return the task
1175	>	*/
1176	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1177	>	return new AdaptedRunnable<T>(runnable, result);
1178	>	}
1179	>
1180	>	/**
1181	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1182	>	* method of the given {@code Callable} as its action, and returns
1183	>	* its result upon {@link #join}, translating any checked exceptions
1184	>	* encountered into {@code RuntimeException}.
1185	>	*
1186	>	* @param callable the callable action
1187	>	* @return the task
1188	>	*/
1189	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1190	>	return new AdaptedCallable<T>(callable);
1191		}
1192
1193		// Serialization support
#	Line 984 | Line 1198 | public abstract class ForkJoinTask<V> im
1198		* Save the state to a stream.
1199		*
1200		* @serialData the current run status and the exception thrown
1201	<	* during execution, or null if none.
1201	>	* during execution, or {@code null} if none
1202		* @param s the stream
1203		*/
1204		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1209 | public abstract class ForkJoinTask<V> im
1209
1210		/**
1211		* Reconstitute the instance from a stream.
1212	+	*
1213		* @param s the stream
1214		*/
1215		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1219 | public abstract class ForkJoinTask<V> im
1219		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1220		Object ex = s.readObject();
1221		if (ex != null)
1222	<	setDoneExceptionally((Throwable)ex);
1222	>	setDoneExceptionally((Throwable) ex);
1223	>	}
1224	>
1225	>	// Unsafe mechanics
1226	>
1227	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1228	>	private static final long statusOffset =
1229	>	objectFieldOffset("status", ForkJoinTask.class);
1230	>
1231	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1232	>	try {
1233	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1234	>	} catch (NoSuchFieldException e) {
1235	>	// Convert Exception to corresponding Error
1236	>	NoSuchFieldError error = new NoSuchFieldError(field);
1237	>	error.initCause(e);
1238	>	throw error;
1239	>	}
1240		}
1241
1242	<	// Temporary Unsafe mechanics for preliminary release
1243	<	private static Unsafe getUnsafe() throws Throwable {
1242	>	/**
1243	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1244	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1245	>	* into a jdk.
1246	>	*
1247	>	* @return a sun.misc.Unsafe
1248	>	*/
1249	>	private static sun.misc.Unsafe getUnsafe() {
1250		try {
1251	<	return Unsafe.getUnsafe();
1251	>	return sun.misc.Unsafe.getUnsafe();
1252		} catch (SecurityException se) {
1253		try {
1254		return java.security.AccessController.doPrivileged
1255	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1256	<	public Unsafe run() throws Exception {
1257	<	return getUnsafePrivileged();
1255	>	(new java.security
1256	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1257	>	public sun.misc.Unsafe run() throws Exception {
1258	>	java.lang.reflect.Field f = sun.misc
1259	>	.Unsafe.class.getDeclaredField("theUnsafe");
1260	>	f.setAccessible(true);
1261	>	return (sun.misc.Unsafe) f.get(null);
1262		}});
1263		} catch (java.security.PrivilegedActionException e) {
1264	<	throw e.getCause();
1264	>	throw new RuntimeException("Could not initialize intrinsics",
1265	>	e.getCause());
1266		}
1267		}
1268		}
1026	–
1027	–	private static Unsafe getUnsafePrivileged()
1028	–	throws NoSuchFieldException, IllegalAccessException {
1029	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1030	–	f.setAccessible(true);
1031	–	return (Unsafe) f.get(null);
1032	–	}
1033	–
1034	–	private static long fieldOffset(String fieldName)
1035	–	throws NoSuchFieldException {
1036	–	return _unsafe.objectFieldOffset
1037	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1038	–	}
1039	–
1040	–	static final Unsafe _unsafe;
1041	–	static final long statusOffset;
1042	–
1043	–	static {
1044	–	try {
1045	–	_unsafe = getUnsafe();
1046	–	statusOffset = fieldOffset("status");
1047	–	} catch (Throwable e) {
1048	–	throw new RuntimeException("Could not initialize intrinsics", e);
1049	–	}
1050	–	}
1051	–
1269		}

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