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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 1.37 by jsr166, Tue Aug 4 20:24:54 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 63 | Line 68 | import java.lang.reflect.*;
68		* execute other tasks while awaiting joins, which is sometimes more
69		* efficient but only applies when all subtasks are known to be
70		* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76		* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	<	* <p> The ForkJoinTask class is not usually directly subclassed.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCancelled} is true if completion was due to cancellation;
84	>	* {@link #isCompletedNormally} is true if a task completed without
85	>	* cancellation or encountering an exception; {@link
86	>	* #isCompletedExceptionally} is true if if the task encountered an
87	>	* exception (in which case {@link #getException} returns the
88	>	* exception); {@link #isCancelled} is true if the task was cancelled
89	>	* (in which case {@link #getException} returns a {@link
90	>	* java.util.concurrent.CancellationException}); and {@link
91	>	* #isCompletedAbnormally} is true if a task was either cancelled or
92	>	* encountered an exception.
93	>	*
94	>	* <p>The ForkJoinTask class is not usually directly subclassed.
95		* Instead, you subclass one of the abstract classes that support a
96	<	* particular style of fork/join processing.  Normally, a concrete
96	>	* particular style of fork/join processing, typically {@link
97	>	* RecursiveAction} for computations that do not return results, or
98	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
99		* ForkJoinTask subclass declares fields comprising its parameters,
100		* established in a constructor, and then defines a {@code compute}
101		* method that somehow uses the control methods supplied by this base
102		* class. While these methods have {@code public} access (to allow
103	<	* instances of different task subclasses to call each others
103	>	* instances of different task subclasses to call each other's
104		* methods), some of them may only be called from within other
105	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
106	<	* exceptions or errors possibly including ClassCastException.
105	>	* ForkJoinTasks (as may be determined using method {@link
106	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
107	>	* result in exceptions or errors, possibly including
108	>	* ClassCastException.
109		*
110	<	* <p>Most base support methods are {@code final} because their
111	<	* implementations are intrinsically tied to the underlying
112	<	* lightweight task scheduling framework, and so cannot be overridden.
113	<	* Developers creating new basic styles of fork/join processing should
114	<	* minimally implement {@code protected} methods
115	<	* {@code exec}, {@code setRawResult}, and
116	<	* {@code getRawResult}, while also introducing an abstract
117	<	* computational method that can be implemented in its subclasses,
118	<	* possibly relying on other {@code protected} methods provided
96	<	* by this class.
110	>	* <p>Most base support methods are {@code final}, to prevent
111	>	* overriding of implementations that are intrinsically tied to the
112	>	* underlying lightweight task scheduling framework.  Developers
113	>	* creating new basic styles of fork/join processing should minimally
114	>	* implement {@code protected} methods {@link #exec}, {@link
115	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
116	>	* an abstract computational method that can be implemented in its
117	>	* subclasses, possibly relying on other {@code protected} methods
118	>	* provided by this class.
119		*
120		* <p>ForkJoinTasks should perform relatively small amounts of
121	<	* computations, otherwise splitting into smaller tasks. As a very
122	<	* rough rule of thumb, a task should perform more than 100 and less
123	<	* than 10000 basic computational steps. If tasks are too big, then
124	<	* parallelism cannot improve throughput. If too small, then memory
125	<	* and internal task maintenance overhead may overwhelm processing.
121	>	* computation. Large tasks should be split into smaller subtasks,
122	>	* usually via recursive decomposition. As a very rough rule of thumb,
123	>	* a task should perform more than 100 and less than 10000 basic
124	>	* computational steps. If tasks are too big, then parallelism cannot
125	>	* improve throughput. If too small, then memory and internal task
126	>	* maintenance overhead may overwhelm processing.
127		*
128	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
129	<	* to be used in extensions such as remote execution frameworks. It is
130	<	* in general sensible to serialize tasks only before or after, but
131	<	* not during execution. Serialization is not relied on during
132	<	* execution itself.
128	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
129	>	* and {@link Callable}, that may be of use when mixing execution of
130	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
131	>	* are of this form, consider using a pool in
132	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
133	>	*
134	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
135	>	* used in extensions such as remote execution frameworks. It is
136	>	* sensible to serialize tasks only before or after, but not during,
137	>	* execution. Serialization is not relied on during execution itself.
138	>	*
139	>	* @since 1.7
140	>	* @author Doug Lea
141		*/
142		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
143
#	Line 141 | Line 172 | public abstract class ForkJoinTask<V> im
172		/**
173		* Table of exceptions thrown by tasks, to enable reporting by
174		* callers. Because exceptions are rare, we don't directly keep
175	<	* them with task objects, but instead us a weak ref table.  Note
175	>	* them with task objects, but instead use a weak ref table.  Note
176		* that cancellation exceptions don't appear in the table, but are
177		* instead recorded as status values.
178	<	* Todo: Use ConcurrentReferenceHashMap
178	>	* TODO: Use ConcurrentReferenceHashMap
179		*/
180		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
181		Collections.synchronizedMap
#	Line 153 | Line 184 | public abstract class ForkJoinTask<V> im
184		// within-package utilities
185
186		/**
187	<	* Get current worker thread, or null if not a worker thread
187	>	* Gets current worker thread, or null if not a worker thread.
188		*/
189		static ForkJoinWorkerThread getWorker() {
190		Thread t = Thread.currentThread();
191	<	return ((t instanceof ForkJoinWorkerThread)?
192	<	(ForkJoinWorkerThread)t : null);
191	>	return ((t instanceof ForkJoinWorkerThread) ?
192	>	(ForkJoinWorkerThread) t : null);
193		}
194
195		final boolean casStatus(int cmp, int val) {
196	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
196	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
197		}
198
199		/**
#	Line 170 | Line 201 | public abstract class ForkJoinTask<V> im
201		*/
202		static void rethrowException(Throwable ex) {
203		if (ex != null)
204	<	_unsafe.throwException(ex);
204	>	UNSAFE.throwException(ex);
205		}
206
207		// Setting completion status
208
209		/**
210	<	* Mark completion and wake up threads waiting to join this task.
210	>	* Marks completion and wakes up threads waiting to join this task.
211	>	*
212		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
213		*/
214		final void setCompletion(int completion) {
215		ForkJoinPool pool = getPool();
216		if (pool != null) {
217		int s; // Clear signal bits while setting completion status
218	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
218	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
219
220		if ((s & SIGNAL_MASK) != 0) {
221		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
222		pool.updateRunningCount(s);
223	<	synchronized(this) { notifyAll(); }
223	>	synchronized (this) { notifyAll(); }
224		}
225		}
226		else
#	Line 201 | Line 233 | public abstract class ForkJoinTask<V> im
233		*/
234		private void externallySetCompletion(int completion) {
235		int s;
236	<	do;while ((s = status) >= 0 &&
237	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
238	<	synchronized(this) { notifyAll(); }
236	>	do {} while ((s = status) >= 0 &&
237	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
238	>	synchronized (this) { notifyAll(); }
239		}
240
241		/**
242	<	* Sets status to indicate normal completion
242	>	* Sets status to indicate normal completion.
243		*/
244		final void setNormalCompletion() {
245		// Try typical fast case -- single CAS, no signal, not already done.
246		// Manually expand casStatus to improve chances of inlining it
247	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
247	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
248		setCompletion(NORMAL);
249		}
250
251		// internal waiting and notification
252
253		/**
254	<	* Performs the actual monitor wait for awaitDone
254	>	* Performs the actual monitor wait for awaitDone.
255		*/
256		private void doAwaitDone() {
257		// Minimize lock bias and in/de-flation effects by maximizing
258		// chances of waiting inside sync
259		try {
260		while (status >= 0)
261	<	synchronized(this) { if (status >= 0) wait(); }
261	>	synchronized (this) { if (status >= 0) wait(); }
262		} catch (InterruptedException ie) {
263		onInterruptedWait();
264		}
265		}
266
267		/**
268	<	* Performs the actual monitor wait for awaitDone
268	>	* Performs the actual timed monitor wait for awaitDone.
269		*/
270		private void doAwaitDone(long startTime, long nanos) {
271	<	synchronized(this) {
271	>	synchronized (this) {
272		try {
273		while (status >= 0) {
274	<	long nt = nanos - System.nanoTime() - startTime;
274	>	long nt = nanos - (System.nanoTime() - startTime);
275		if (nt <= 0)
276		break;
277	<	wait(nt / 1000000, (int)(nt % 1000000));
277	>	wait(nt / 1000000, (int) (nt % 1000000));
278		}
279		} catch (InterruptedException ie) {
280		onInterruptedWait();
#	Line 255 | Line 287 | public abstract class ForkJoinTask<V> im
287		/**
288		* Sets status to indicate there is joiner, then waits for join,
289		* surrounded with pool notifications.
290	+	*
291		* @return status upon exit
292		*/
293	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
294	<	ForkJoinPool pool = w == null? null : w.pool;
293	>	private int awaitDone(ForkJoinWorkerThread w,
294	>	boolean maintainParallelism) {
295	>	ForkJoinPool pool = (w == null) ? null : w.pool;
296		int s;
297		while ((s = status) >= 0) {
298	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
298	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
299		if (pool == null || !pool.preJoin(this, maintainParallelism))
300		doAwaitDone();
301		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 308 | public abstract class ForkJoinTask<V> im
308
309		/**
310		* Timed version of awaitDone
311	+	*
312		* @return status upon exit
313		*/
314		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
315	<	ForkJoinPool pool = w == null? null : w.pool;
315	>	ForkJoinPool pool = (w == null) ? null : w.pool;
316		int s;
317		while ((s = status) >= 0) {
318	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
318	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
319		long startTime = System.nanoTime();
320		if (pool == null || !pool.preJoin(this, false))
321		doAwaitDone(startTime, nanos);
#	Line 297 | Line 332 | public abstract class ForkJoinTask<V> im
332		}
333
334		/**
335	<	* Notify pool that thread is unblocked. Called by signalled
335	>	* Notifies pool that thread is unblocked. Called by signalled
336		* threads when woken by non-FJ threads (which is atypical).
337		*/
338		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
339		int s;
340	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
340	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
341		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
342		pool.updateRunningCount(s);
343		}
344
345		/**
346	<	* Notify pool to adjust counts on cancelled or timed out wait
346	>	* Notifies pool to adjust counts on cancelled or timed out wait.
347		*/
348		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
349		if (pool != null) {
#	Line 323 | Line 358 | public abstract class ForkJoinTask<V> im
358		}
359
360		/**
361	<	* Handle interruptions during waits.
361	>	* Handles interruptions during waits.
362		*/
363		private void onInterruptedWait() {
364		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 377 | public abstract class ForkJoinTask<V> im
377		}
378
379		/**
380	<	* Throws the exception associated with status s;
380	>	* Throws the exception associated with status s.
381	>	*
382		* @throws the exception
383		*/
384		private void reportException(int s) {
#	Line 355 | Line 391 | public abstract class ForkJoinTask<V> im
391		}
392
393		/**
394	<	* Returns result or throws exception using j.u.c.Future conventions
395	<	* Only call when isDone known to be true.
394	>	* Returns result or throws exception using j.u.c.Future conventions.
395	>	* Only call when {@code isDone} known to be true.
396		*/
397		private V reportFutureResult()
398	<	throws ExecutionException, InterruptedException {
398	>	throws InterruptedException, ExecutionException {
399	>	if (Thread.interrupted())
400	>	throw new InterruptedException();
401		int s = status & COMPLETION_MASK;
402		if (s < NORMAL) {
403		Throwable ex;
#	Line 367 | Line 405 | public abstract class ForkJoinTask<V> im
405		throw new CancellationException();
406		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
407		throw new ExecutionException(ex);
370	–	if (Thread.interrupted())
371	–	throw new InterruptedException();
408		}
409		return getRawResult();
410		}
411
412		/**
413		* Returns result or throws exception using j.u.c.Future conventions
414	<	* with timeouts
414	>	* with timeouts.
415		*/
416		private V reportTimedFutureResult()
417		throws InterruptedException, ExecutionException, TimeoutException {
418	+	if (Thread.interrupted())
419	+	throw new InterruptedException();
420		Throwable ex;
421		int s = status & COMPLETION_MASK;
422		if (s == NORMAL)
423		return getRawResult();
424	<	if (s == CANCELLED)
424	>	else if (s == CANCELLED)
425		throw new CancellationException();
426	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427		throw new ExecutionException(ex);
428	<	if (Thread.interrupted())
429	<	throw new InterruptedException();
392	<	throw new TimeoutException();
428	>	else
429	>	throw new TimeoutException();
430		}
431
432		// internal execution methods
433
434		/**
435		* Calls exec, recording completion, and rethrowing exception if
436	<	* encountered. Caller should normally check status before calling
436	>	* encountered. Caller should normally check status before calling.
437	>	*
438		* @return true if completed normally
439		*/
440		private boolean tryExec() {
#	Line 414 | Line 452 | public abstract class ForkJoinTask<V> im
452
453		/**
454		* Main execution method used by worker threads. Invokes
455	<	* base computation unless already complete
455	>	* base computation unless already complete.
456		*/
457		final void quietlyExec() {
458		if (status >= 0) {
459		try {
460		if (!exec())
461		return;
462	<	} catch(Throwable rex) {
462	>	} catch (Throwable rex) {
463		setDoneExceptionally(rex);
464		return;
465		}
#	Line 430 | Line 468 | public abstract class ForkJoinTask<V> im
468		}
469
470		/**
471	<	* Calls exec, recording but not rethrowing exception
472	<	* Caller should normally check status before calling
471	>	* Calls exec(), recording but not rethrowing exception.
472	>	* Caller should normally check status before calling.
473	>	*
474		* @return true if completed normally
475		*/
476		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 486 | public abstract class ForkJoinTask<V> im
486		}
487
488		/**
489	<	* Cancel, ignoring any exceptions it throws
489	>	* Cancels, ignoring any exceptions it throws.
490		*/
491		final void cancelIgnoringExceptions() {
492		try {
493		cancel(false);
494	<	} catch(Throwable ignore) {
494	>	} catch (Throwable ignore) {
495		}
496		}
497
#	Line 464 | Line 503 | public abstract class ForkJoinTask<V> im
503		ForkJoinTask<?> t;
504		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
505		t.quietlyExec();
506	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
506	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
507		}
508
509		// public methods
#	Line 472 | Line 511 | public abstract class ForkJoinTask<V> im
511		/**
512		* Arranges to asynchronously execute this task.  While it is not
513		* necessarily enforced, it is a usage error to fork a task more
514	<	* than once unless it has completed and been reinitialized.  This
515	<	* method may be invoked only from within ForkJoinTask
516	<	* computations. Attempts to invoke in other contexts result in
517	<	* exceptions or errors possibly including ClassCastException.
514	>	* than once unless it has completed and been reinitialized.
515	>	*
516	>	* <p>This method may be invoked only from within {@code
517	>	* ForkJoinTask} computations (as may be determined using method
518	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
519	>	* result in exceptions or errors, possibly including {@code
520	>	* ClassCastException}.
521	>	*
522	>	* @return {@code this}, to simplify usage
523		*/
524	<	public final void fork() {
525	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
524	>	public final ForkJoinTask<V> fork() {
525	>	((ForkJoinWorkerThread) Thread.currentThread())
526	>	.pushTask(this);
527	>	return this;
528		}
529
530		/**
531		* Returns the result of the computation when it is ready.
532	<	* This method differs from {@code get} in that abnormal
533	<	* completion results in RuntimeExceptions or Errors, not
534	<	* ExecutionExceptions.
532	>	* This method differs from {@link #get()} in that
533	>	* abnormal completion results in {@code RuntimeException} or
534	>	* {@code Error}, not {@code ExecutionException}.
535		*
536		* @return the computed result
537		*/
#	Line 498 | Line 544 | public abstract class ForkJoinTask<V> im
544
545		/**
546		* Commences performing this task, awaits its completion if
547	<	* necessary, and return its result.
548	<	* @throws Throwable (a RuntimeException, Error, or unchecked
549	<	* exception) if the underlying computation did so.
547	>	* necessary, and return its result, or throws an (unchecked)
548	>	* exception if the underlying computation did so.
549	>	*
550		* @return the computed result
551		*/
552		public final V invoke() {
#	Line 511 | Line 557 | public abstract class ForkJoinTask<V> im
557		}
558
559		/**
560	<	* Forks both tasks, returning when {@code isDone} holds for
561	<	* both of them or an exception is encountered. This method may be
562	<	* invoked only from within ForkJoinTask computations. Attempts to
563	<	* invoke in other contexts result in exceptions or errors
564	<	* possibly including ClassCastException.
565	<	* @param t1 one task
566	<	* @param t2 the other task
567	<	* @throws NullPointerException if t1 or t2 are null
568	<	* @throws RuntimeException or Error if either task did so.
560	>	* Forks the given tasks, returning when {@code isDone} holds for
561	>	* each task or an (unchecked) exception is encountered, in which
562	>	* case the exception is rethrown.  If more than one task
563	>	* encounters an exception, then this method throws any one of
564	>	* these exceptions.  The individual status of each task may be
565	>	* checked using {@link #getException()} and related methods.
566	>	*
567	>	* <p>This method may be invoked only from within {@code
568	>	* ForkJoinTask} computations (as may be determined using method
569	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
570	>	* result in exceptions or errors, possibly including {@code
571	>	* ClassCastException}.
572	>	*
573	>	* @param t1 the first task
574	>	* @param t2 the second task
575	>	* @throws NullPointerException if any task is null
576		*/
577	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
577	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
578		t2.fork();
579		t1.invoke();
580		t2.join();
581		}
582
583		/**
584	<	* Forks the given tasks, returning when {@code isDone} holds
585	<	* for all of them. If any task encounters an exception, others
586	<	* may be cancelled.  This method may be invoked only from within
587	<	* ForkJoinTask computations. Attempts to invoke in other contexts
588	<	* result in exceptions or errors possibly including ClassCastException.
589	<	* @param tasks the array of tasks
590	<	* @throws NullPointerException if tasks or any element are null.
591	<	* @throws RuntimeException or Error if any task did so.
584	>	* Forks the given tasks, returning when {@code isDone} holds for
585	>	* each task or an (unchecked) exception is encountered, in which
586	>	* case the exception is rethrown. If any task encounters an
587	>	* exception, others may be, but are not guaranteed to be,
588	>	* cancelled.  If more than one task encounters an exception, then
589	>	* this method throws any one of these exceptions.  The individual
590	>	* status of each task may be checked using {@link #getException()}
591	>	* and related methods.
592	>	*
593	>	* <p>This method may be invoked only from within {@code
594	>	* ForkJoinTask} computations (as may be determined using method
595	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
596	>	* result in exceptions or errors, possibly including {@code
597	>	* ClassCastException}.
598	>	*
599	>	* @param tasks the tasks
600	>	* @throws NullPointerException if any task is null
601		*/
602		public static void invokeAll(ForkJoinTask<?>... tasks) {
603		Throwable ex = null;
#	Line 571 | Line 633 | public abstract class ForkJoinTask<V> im
633		}
634
635		/**
636	<	* Forks all tasks in the collection, returning when
637	<	* {@code isDone} holds for all of them. If any task
638	<	* encounters an exception, others may be cancelled.  This method
639	<	* may be invoked only from within ForkJoinTask
640	<	* computations. Attempts to invoke in other contexts result in
641	<	* exceptions or errors possibly including ClassCastException.
636	>	* Forks all tasks in the specified collection, returning when
637	>	* {@code isDone} holds for each task or an (unchecked) exception
638	>	* is encountered.  If any task encounters an exception, others
639	>	* may be, but are not guaranteed to be, cancelled.  If more than
640	>	* one task encounters an exception, then this method throws any
641	>	* one of these exceptions.  The individual status of each task
642	>	* may be checked using {@link #getException()} and related
643	>	* methods.  The behavior of this operation is undefined if the
644	>	* specified collection is modified while the operation is in
645	>	* progress.
646	>	*
647	>	* <p>This method may be invoked only from within {@code
648	>	* ForkJoinTask} computations (as may be determined using method
649	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
650	>	* result in exceptions or errors, possibly including {@code
651	>	* ClassCastException}.
652	>	*
653		* @param tasks the collection of tasks
654	<	* @throws NullPointerException if tasks or any element are null.
655	<	* @throws RuntimeException or Error if any task did so.
654	>	* @return the tasks argument, to simplify usage
655	>	* @throws NullPointerException if tasks or any element are null
656		*/
657	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
658	<	if (!(tasks instanceof List)) {
659	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
660	<	return;
657	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
658	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
659	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
660	>	return tasks;
661		}
662	+	@SuppressWarnings("unchecked")
663		List<? extends ForkJoinTask<?>> ts =
664	<	(List<? extends ForkJoinTask<?>>)tasks;
664	>	(List<? extends ForkJoinTask<?>>) tasks;
665		Throwable ex = null;
666		int last = ts.size() - 1;
667		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 692 | public abstract class ForkJoinTask<V> im
692		}
693		if (ex != null)
694		rethrowException(ex);
695	+	return tasks;
696		}
697
698		/**
699	<	* Returns true if the computation performed by this task has
700	<	* completed (or has been cancelled).
701	<	* @return true if this computation has completed
702	<	*/
703	<	public final boolean isDone() {
704	<	return status < 0;
705	<	}
631	<
632	<	/**
633	<	* Returns true if this task was cancelled.
634	<	* @return true if this task was cancelled
635	<	*/
636	<	public final boolean isCancelled() {
637	<	return (status & COMPLETION_MASK) == CANCELLED;
638	<	}
639	<
640	<	/**
641	<	* Asserts that the results of this task's computation will not be
642	<	* used. If a cancellation occurs before attempting to execute this
643	<	* task, then execution will be suppressed, {@code isCancelled}
644	<	* will report true, and {@code join} will result in a
645	<	* {@code CancellationException} being thrown. Otherwise, when
646	<	* cancellation races with completion, there are no guarantees
647	<	* about whether {@code isCancelled} will report true, whether
648	<	* {@code join} will return normally or via an exception, or
649	<	* whether these behaviors will remain consistent upon repeated
650	<	* invocation.
699	>	* Attempts to cancel execution of this task. This attempt will
700	>	* fail if the task has already completed, has already been
701	>	* cancelled, or could not be cancelled for some other reason. If
702	>	* successful, and this task has not started when cancel is
703	>	* called, execution of this task is suppressed, {@link
704	>	* #isCancelled} will report true, and {@link #join} will result
705	>	* in a {@code CancellationException} being thrown.
706		*
707		* <p>This method may be overridden in subclasses, but if so, must
708		* still ensure that these minimal properties hold. In particular,
709	<	* the cancel method itself must not throw exceptions.
709	>	* the {@code cancel} method itself must not throw exceptions.
710		*
711	<	* <p> This method is designed to be invoked by <em>other</em>
711	>	* <p>This method is designed to be invoked by <em>other</em>
712		* tasks. To terminate the current task, you can just return or
713		* throw an unchecked exception from its computation method, or
714	<	* invoke {@code completeExceptionally}.
714	>	* invoke {@link #completeExceptionally}.
715		*
716		* @param mayInterruptIfRunning this value is ignored in the
717	<	* default implementation because tasks are not in general
718	<	* cancelled via interruption.
717	>	* default implementation because tasks are not
718	>	* cancelled via interruption
719		*
720	<	* @return true if this task is now cancelled
720	>	* @return {@code true} if this task is now cancelled
721		*/
722		public boolean cancel(boolean mayInterruptIfRunning) {
723		setCompletion(CANCELLED);
#	Line 670 | Line 725 | public abstract class ForkJoinTask<V> im
725		}
726
727		/**
728	<	* Returns true if this task threw an exception or was cancelled
729	<	* @return true if this task threw an exception or was cancelled
728	>	* Returns {@code true} if the computation performed by this task
729	>	* has completed (or has been cancelled).
730	>	*
731	>	* @return {@code true} if this computation has completed
732	>	*/
733	>	public final boolean isDone() {
734	>	return status < 0;
735	>	}
736	>
737	>	/**
738	>	* Returns {@code true} if this task was cancelled.
739	>	*
740	>	* @return {@code true} if this task was cancelled
741	>	*/
742	>	public final boolean isCancelled() {
743	>	return (status & COMPLETION_MASK) == CANCELLED;
744	>	}
745	>
746	>	/**
747	>	* Returns {@code true} if this task threw an exception or was cancelled.
748	>	*
749	>	* @return {@code true} if this task threw an exception or was cancelled
750		*/
751		public final boolean isCompletedAbnormally() {
752		return (status & COMPLETION_MASK) < NORMAL;
753		}
754
755		/**
756	+	* Returns {@code true} if this task completed without throwing an
757	+	* exception and was not cancelled.
758	+	*
759	+	* @return {@code true} if this task completed without throwing an
760	+	* exception and was not cancelled
761	+	*/
762	+	public final boolean isCompletedNormally() {
763	+	return (status & COMPLETION_MASK) == NORMAL;
764	+	}
765	+
766	+	/**
767	+	* Returns {@code true} if this task threw an exception.
768	+	*
769	+	* @return {@code true} if this task threw an exception
770	+	*/
771	+	public final boolean isCompletedExceptionally() {
772	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
773	+	}
774	+
775	+	/**
776		* Returns the exception thrown by the base computation, or a
777	<	* CancellationException if cancelled, or null if none or if the
778	<	* method has not yet completed.
779	<	* @return the exception, or null if none
777	>	* {@code CancellationException} if cancelled, or {@code null} if
778	>	* none or if the method has not yet completed.
779	>	*
780	>	* @return the exception, or {@code null} if none
781		*/
782		public final Throwable getException() {
783		int s = status & COMPLETION_MASK;
784	<	if (s >= NORMAL)
785	<	return null;
786	<	if (s == CANCELLED)
691	<	return new CancellationException();
692	<	return exceptionMap.get(this);
784	>	return ((s >= NORMAL)    ? null :
785	>	(s == CANCELLED) ? new CancellationException() :
786	>	exceptionMap.get(this));
787		}
788
789		/**
#	Line 698 | Line 792 | public abstract class ForkJoinTask<V> im
792		* {@code join} and related operations. This method may be used
793		* to induce exceptions in asynchronous tasks, or to force
794		* completion of tasks that would not otherwise complete.  Its use
795	<	* in other situations is likely to be wrong.  This method is
795	>	* in other situations is discouraged.  This method is
796		* overridable, but overridden versions must invoke {@code super}
797		* implementation to maintain guarantees.
798		*
#	Line 708 | Line 802 | public abstract class ForkJoinTask<V> im
802		*/
803		public void completeExceptionally(Throwable ex) {
804		setDoneExceptionally((ex instanceof RuntimeException) ||
805	<	(ex instanceof Error)? ex :
805	>	(ex instanceof Error) ? ex :
806		new RuntimeException(ex));
807		}
808
#	Line 718 | Line 812 | public abstract class ForkJoinTask<V> im
812		* operations. This method may be used to provide results for
813		* asynchronous tasks, or to provide alternative handling for
814		* tasks that would not otherwise complete normally. Its use in
815	<	* other situations is likely to be wrong. This method is
815	>	* other situations is discouraged. This method is
816		* overridable, but overridden versions must invoke {@code super}
817		* implementation to maintain guarantees.
818		*
819	<	* @param value the result value for this task.
819	>	* @param value the result value for this task
820		*/
821		public void complete(V value) {
822		try {
823		setRawResult(value);
824	<	} catch(Throwable rex) {
824	>	} catch (Throwable rex) {
825		setDoneExceptionally(rex);
826		return;
827		}
#	Line 743 | Line 837 | public abstract class ForkJoinTask<V> im
837
838		public final V get(long timeout, TimeUnit unit)
839		throws InterruptedException, ExecutionException, TimeoutException {
840	+	long nanos = unit.toNanos(timeout);
841		ForkJoinWorkerThread w = getWorker();
842		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
843	<	awaitDone(w, unit.toNanos(timeout));
843	>	awaitDone(w, nanos);
844		return reportTimedFutureResult();
845		}
846
#	Line 756 | Line 851 | public abstract class ForkJoinTask<V> im
851		* there are no potential dependencies between continuation of the
852		* current task and that of any other task that might be executed
853		* while helping. (This usually holds for pure divide-and-conquer
854	<	* tasks). This method may be invoked only from within
855	<	* ForkJoinTask computations. Attempts to invoke in other contexts
856	<	* result in exceptions or errors possibly including ClassCastException.
854	>	* tasks).
855	>	*
856	>	* <p>This method may be invoked only from within {@code
857	>	* ForkJoinTask} computations (as may be determined using method
858	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
859	>	* result in exceptions or errors, possibly including {@code
860	>	* ClassCastException}.
861	>	*
862		* @return the computed result
863		*/
864		public final V helpJoin() {
865	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
865	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
866		if (status < 0 || !w.unpushTask(this) || !tryExec())
867		reportException(busyJoin(w));
868		return getRawResult();
#	Line 770 | Line 870 | public abstract class ForkJoinTask<V> im
870
871		/**
872		* Possibly executes other tasks until this task is ready.  This
873	<	* method may be invoked only from within ForkJoinTask
874	<	* computations. Attempts to invoke in other contexts result in
875	<	* exceptions or errors possibly including ClassCastException.
873	>	* method may be useful when processing collections of tasks when
874	>	* some have been cancelled or otherwise known to have aborted.
875	>	*
876	>	* <p>This method may be invoked only from within {@code
877	>	* ForkJoinTask} computations (as may be determined using method
878	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
879	>	* result in exceptions or errors, possibly including {@code
880	>	* ClassCastException}.
881		*/
882		public final void quietlyHelpJoin() {
883		if (status >= 0) {
884		ForkJoinWorkerThread w =
885	<	(ForkJoinWorkerThread)(Thread.currentThread());
885	>	(ForkJoinWorkerThread) Thread.currentThread();
886		if (!w.unpushTask(this) || !tryQuietlyInvoke())
887		busyJoin(w);
888		}
#	Line 811 | Line 916 | public abstract class ForkJoinTask<V> im
916
917		/**
918		* Possibly executes tasks until the pool hosting the current task
919	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
920	<	* designs in which many tasks are forked, but none are explicitly
921	<	* joined, instead executing them until all are processed.
919	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
920	>	* be of use in designs in which many tasks are forked, but none
921	>	* are explicitly joined, instead executing them until all are
922	>	* processed.
923	>	*
924	>	* <p>This method may be invoked only from within {@code
925	>	* ForkJoinTask} computations (as may be determined using method
926	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
927	>	* result in exceptions or errors, possibly including {@code
928	>	* ClassCastException}.
929		*/
930		public static void helpQuiesce() {
931	<	((ForkJoinWorkerThread)(Thread.currentThread())).
932	<	helpQuiescePool();
931	>	((ForkJoinWorkerThread) Thread.currentThread())
932	>	.helpQuiescePool();
933		}
934
935		/**
#	Line 826 | Line 938 | public abstract class ForkJoinTask<V> im
938		* this task, but only if reuse occurs when this task has either
939		* never been forked, or has been forked, then completed and all
940		* outstanding joins of this task have also completed. Effects
941	<	* under any other usage conditions are not guaranteed, and are
942	<	* almost surely wrong. This method may be useful when executing
941	>	* under any other usage conditions are not guaranteed.
942	>	* This method may be useful when executing
943		* pre-constructed trees of subtasks in loops.
944		*/
945		public void reinitialize() {
#	Line 838 | Line 950 | public abstract class ForkJoinTask<V> im
950
951		/**
952		* Returns the pool hosting the current task execution, or null
953	<	* if this task is executing outside of any pool.
954	<	* @return the pool, or null if none.
953	>	* if this task is executing outside of any ForkJoinPool.
954	>	*
955	>	* @see #inForkJoinPool
956	>	* @return the pool, or {@code null} if none
957		*/
958		public static ForkJoinPool getPool() {
959		Thread t = Thread.currentThread();
960	<	return ((t instanceof ForkJoinWorkerThread)?
961	<	((ForkJoinWorkerThread)t).pool : null);
960	>	return (t instanceof ForkJoinWorkerThread) ?
961	>	((ForkJoinWorkerThread) t).pool : null;
962	>	}
963	>
964	>	/**
965	>	* Returns {@code true} if the current thread is executing as a
966	>	* ForkJoinPool computation.
967	>	*
968	>	* @return {@code true} if the current thread is executing as a
969	>	* ForkJoinPool computation, or false otherwise
970	>	*/
971	>	public static boolean inForkJoinPool() {
972	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
973		}
974
975		/**
#	Line 853 | Line 978 | public abstract class ForkJoinTask<V> im
978		* by the current thread, and has not commenced executing in
979		* another thread.  This method may be useful when arranging
980		* alternative local processing of tasks that could have been, but
981	<	* were not, stolen. This method may be invoked only from within
982	<	* ForkJoinTask computations. Attempts to invoke in other contexts
983	<	* result in exceptions or errors possibly including ClassCastException.
984	<	* @return true if unforked
981	>	* were not, stolen.
982	>	*
983	>	* <p>This method may be invoked only from within {@code
984	>	* ForkJoinTask} computations (as may be determined using method
985	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
986	>	* result in exceptions or errors, possibly including {@code
987	>	* ClassCastException}.
988	>	*
989	>	* @return {@code true} if unforked
990		*/
991		public boolean tryUnfork() {
992	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
992	>	return ((ForkJoinWorkerThread) Thread.currentThread())
993	>	.unpushTask(this);
994		}
995
996		/**
#	Line 867 | Line 998 | public abstract class ForkJoinTask<V> im
998		* forked by the current worker thread but not yet executed. This
999		* value may be useful for heuristic decisions about whether to
1000		* fork other tasks.
1001	+	*
1002	+	* <p>This method may be invoked only from within {@code
1003	+	* ForkJoinTask} computations (as may be determined using method
1004	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1005	+	* result in exceptions or errors, possibly including {@code
1006	+	* ClassCastException}.
1007	+	*
1008		* @return the number of tasks
1009		*/
1010		public static int getQueuedTaskCount() {
1011	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1012	<	getQueueSize();
1011	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1012	>	.getQueueSize();
1013		}
1014
1015		/**
1016	<	* Returns a estimate of how many more locally queued tasks are
1016	>	* Returns an estimate of how many more locally queued tasks are
1017		* held by the current worker thread than there are other worker
1018		* threads that might steal them.  This value may be useful for
1019		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 1021 | public abstract class ForkJoinTask<V> im
1021		* aim to maintain a small constant surplus (for example, 3) of
1022		* tasks, and to process computations locally if this threshold is
1023		* exceeded.
1024	+	*
1025	+	* <p>This method may be invoked only from within {@code
1026	+	* ForkJoinTask} computations (as may be determined using method
1027	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1028	+	* result in exceptions or errors, possibly including {@code
1029	+	* ClassCastException}.
1030	+	*
1031		* @return the surplus number of tasks, which may be negative
1032		*/
1033		public static int getSurplusQueuedTaskCount() {
1034	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
1034	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1035		.getEstimatedSurplusTaskCount();
1036		}
1037
1038		// Extension methods
1039
1040		/**
1041	<	* Returns the result that would be returned by {@code join},
1042	<	* even if this task completed abnormally, or null if this task is
1043	<	* not known to have been completed.  This method is designed to
1044	<	* aid debugging, as well as to support extensions. Its use in any
1045	<	* other context is discouraged.
1041	>	* Returns the result that would be returned by {@link #join}, even
1042	>	* if this task completed abnormally, or {@code null} if this task
1043	>	* is not known to have been completed.  This method is designed
1044	>	* to aid debugging, as well as to support extensions. Its use in
1045	>	* any other context is discouraged.
1046		*
1047	<	* @return the result, or null if not completed.
1047	>	* @return the result, or {@code null} if not completed
1048		*/
1049		public abstract V getRawResult();
1050
#	Line 918 | Line 1063 | public abstract class ForkJoinTask<V> im
1063		* called otherwise. The return value controls whether this task
1064		* is considered to be done normally. It may return false in
1065		* asynchronous actions that require explicit invocations of
1066	<	* {@code complete} to become joinable. It may throw exceptions
1067	<	* to indicate abnormal exit.
1068	<	* @return true if completed normally
1069	<	* @throws Error or RuntimeException if encountered during computation
1066	>	* {@link #complete} to become joinable. It may also throw an
1067	>	* (unchecked) exception to indicate abnormal exit.
1068	>	*
1069	>	* @return {@code true} if completed normally
1070		*/
1071		protected abstract boolean exec();
1072
1073		/**
1074	<	* Returns, but does not unschedule or execute, the task queued by
1075	<	* the current thread but not yet executed, if one is
1074	>	* Returns, but does not unschedule or execute, a task queued by
1075	>	* the current thread but not yet executed, if one is immediately
1076		* available. There is no guarantee that this task will actually
1077	<	* be polled or executed next.  This method is designed primarily
1078	<	* to support extensions, and is unlikely to be useful otherwise.
1079	<	* This method may be invoked only from within ForkJoinTask
1080	<	* computations. Attempts to invoke in other contexts result in
1081	<	* exceptions or errors possibly including ClassCastException.
1077	>	* be polled or executed next. Conversely, this method may return
1078	>	* null even if a task exists but cannot be accessed without
1079	>	* contention with other threads.  This method is designed
1080	>	* primarily to support extensions, and is unlikely to be useful
1081	>	* otherwise.
1082	>	*
1083	>	* <p>This method may be invoked only from within {@code
1084	>	* ForkJoinTask} computations (as may be determined using method
1085	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1086	>	* result in exceptions or errors, possibly including {@code
1087	>	* ClassCastException}.
1088		*
1089	<	* @return the next task, or null if none are available
1089	>	* @return the next task, or {@code null} if none are available
1090		*/
1091		protected static ForkJoinTask<?> peekNextLocalTask() {
1092	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
1092	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1093	>	.peekTask();
1094		}
1095
1096		/**
1097		* Unschedules and returns, without executing, the next task
1098		* queued by the current thread but not yet executed.  This method
1099		* is designed primarily to support extensions, and is unlikely to
1100	<	* be useful otherwise.  This method may be invoked only from
949	<	* within ForkJoinTask computations. Attempts to invoke in other
950	<	* contexts result in exceptions or errors possibly including
951	<	* ClassCastException.
1100	>	* be useful otherwise.
1101		*
1102	<	* @return the next task, or null if none are available
1102	>	* <p>This method may be invoked only from within {@code
1103	>	* ForkJoinTask} computations (as may be determined using method
1104	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1105	>	* result in exceptions or errors, possibly including {@code
1106	>	* ClassCastException}.
1107	>	*
1108	>	* @return the next task, or {@code null} if none are available
1109		*/
1110		protected static ForkJoinTask<?> pollNextLocalTask() {
1111	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1111	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1112	>	.pollLocalTask();
1113		}
1114
1115		/**
#	Line 964 | Line 1120 | public abstract class ForkJoinTask<V> im
1120		* {@code null} result does not necessarily imply quiescence
1121		* of the pool this task is operating in.  This method is designed
1122		* primarily to support extensions, and is unlikely to be useful
1123	<	* otherwise.  This method may be invoked only from within
1124	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1125	<	* result in exceptions or errors possibly including
1126	<	* ClassCastException.
1123	>	* otherwise.
1124	>	*
1125	>	* <p>This method may be invoked only from within {@code
1126	>	* ForkJoinTask} computations (as may be determined using method
1127	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1128	>	* result in exceptions or errors, possibly including {@code
1129	>	* ClassCastException}.
1130		*
1131	<	* @return a task, or null if none are available
1131	>	* @return a task, or {@code null} if none are available
1132		*/
1133		protected static ForkJoinTask<?> pollTask() {
1134	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1135	<	pollTask();
1134	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1135	>	.pollTask();
1136	>	}
1137	>
1138	>	/**
1139	>	* Adaptor for Runnables. This implements RunnableFuture
1140	>	* to be compliant with AbstractExecutorService constraints
1141	>	* when used in ForkJoinPool.
1142	>	*/
1143	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1144	>	implements RunnableFuture<T> {
1145	>	final Runnable runnable;
1146	>	final T resultOnCompletion;
1147	>	T result;
1148	>	AdaptedRunnable(Runnable runnable, T result) {
1149	>	if (runnable == null) throw new NullPointerException();
1150	>	this.runnable = runnable;
1151	>	this.resultOnCompletion = result;
1152	>	}
1153	>	public T getRawResult() { return result; }
1154	>	public void setRawResult(T v) { result = v; }
1155	>	public boolean exec() {
1156	>	runnable.run();
1157	>	result = resultOnCompletion;
1158	>	return true;
1159	>	}
1160	>	public void run() { invoke(); }
1161	>	private static final long serialVersionUID = 5232453952276885070L;
1162	>	}
1163	>
1164	>	/**
1165	>	* Adaptor for Callables
1166	>	*/
1167	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1168	>	implements RunnableFuture<T> {
1169	>	final Callable<? extends T> callable;
1170	>	T result;
1171	>	AdaptedCallable(Callable<? extends T> callable) {
1172	>	if (callable == null) throw new NullPointerException();
1173	>	this.callable = callable;
1174	>	}
1175	>	public T getRawResult() { return result; }
1176	>	public void setRawResult(T v) { result = v; }
1177	>	public boolean exec() {
1178	>	try {
1179	>	result = callable.call();
1180	>	return true;
1181	>	} catch (Error err) {
1182	>	throw err;
1183	>	} catch (RuntimeException rex) {
1184	>	throw rex;
1185	>	} catch (Exception ex) {
1186	>	throw new RuntimeException(ex);
1187	>	}
1188	>	}
1189	>	public void run() { invoke(); }
1190	>	private static final long serialVersionUID = 2838392045355241008L;
1191	>	}
1192	>
1193	>	/**
1194	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1195	>	* method of the given {@code Runnable} as its action, and returns
1196	>	* a null result upon {@link #join}.
1197	>	*
1198	>	* @param runnable the runnable action
1199	>	* @return the task
1200	>	*/
1201	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1202	>	return new AdaptedRunnable<Void>(runnable, null);
1203	>	}
1204	>
1205	>	/**
1206	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1207	>	* method of the given {@code Runnable} as its action, and returns
1208	>	* the given result upon {@link #join}.
1209	>	*
1210	>	* @param runnable the runnable action
1211	>	* @param result the result upon completion
1212	>	* @return the task
1213	>	*/
1214	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1215	>	return new AdaptedRunnable<T>(runnable, result);
1216	>	}
1217	>
1218	>	/**
1219	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1220	>	* method of the given {@code Callable} as its action, and returns
1221	>	* its result upon {@link #join}, translating any checked exceptions
1222	>	* encountered into {@code RuntimeException}.
1223	>	*
1224	>	* @param callable the callable action
1225	>	* @return the task
1226	>	*/
1227	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1228	>	return new AdaptedCallable<T>(callable);
1229		}
1230
1231		// Serialization support
#	Line 984 | Line 1236 | public abstract class ForkJoinTask<V> im
1236		* Save the state to a stream.
1237		*
1238		* @serialData the current run status and the exception thrown
1239	<	* during execution, or null if none.
1239	>	* during execution, or {@code null} if none
1240		* @param s the stream
1241		*/
1242		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1247 | public abstract class ForkJoinTask<V> im
1247
1248		/**
1249		* Reconstitute the instance from a stream.
1250	+	*
1251		* @param s the stream
1252		*/
1253		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1257 | public abstract class ForkJoinTask<V> im
1257		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1258		Object ex = s.readObject();
1259		if (ex != null)
1260	<	setDoneExceptionally((Throwable)ex);
1260	>	setDoneExceptionally((Throwable) ex);
1261	>	}
1262	>
1263	>	// Unsafe mechanics
1264	>
1265	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1266	>	private static final long statusOffset =
1267	>	objectFieldOffset("status", ForkJoinTask.class);
1268	>
1269	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1270	>	try {
1271	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1272	>	} catch (NoSuchFieldException e) {
1273	>	// Convert Exception to corresponding Error
1274	>	NoSuchFieldError error = new NoSuchFieldError(field);
1275	>	error.initCause(e);
1276	>	throw error;
1277	>	}
1278		}
1279
1280	<	// Temporary Unsafe mechanics for preliminary release
1281	<	private static Unsafe getUnsafe() throws Throwable {
1280	>	/**
1281	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1282	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1283	>	* into a jdk.
1284	>	*
1285	>	* @return a sun.misc.Unsafe
1286	>	*/
1287	>	private static sun.misc.Unsafe getUnsafe() {
1288		try {
1289	<	return Unsafe.getUnsafe();
1289	>	return sun.misc.Unsafe.getUnsafe();
1290		} catch (SecurityException se) {
1291		try {
1292		return java.security.AccessController.doPrivileged
1293	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1294	<	public Unsafe run() throws Exception {
1295	<	return getUnsafePrivileged();
1293	>	(new java.security
1294	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1295	>	public sun.misc.Unsafe run() throws Exception {
1296	>	java.lang.reflect.Field f = sun.misc
1297	>	.Unsafe.class.getDeclaredField("theUnsafe");
1298	>	f.setAccessible(true);
1299	>	return (sun.misc.Unsafe) f.get(null);
1300		}});
1301		} catch (java.security.PrivilegedActionException e) {
1302	<	throw e.getCause();
1302	>	throw new RuntimeException("Could not initialize intrinsics",
1303	>	e.getCause());
1304		}
1305		}
1306		}
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	–
1307		}

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