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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.70 by dl, Tue Nov 23 00:10:39 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	+
9		import java.io.Serializable;
10	<	import java.util.*;
11	<	import java.util.concurrent.*;
12	<	import java.util.concurrent.atomic.*;
13	<	import sun.misc.Unsafe;
14	<	import java.lang.reflect.*;
10	>	import java.util.Collection;
11	>	import java.util.Collections;
12	>	import java.util.List;
13	>	import java.util.RandomAccess;
14	>	import java.util.Map;
15	>	import java.util.WeakHashMap;
16	>	import java.util.concurrent.Callable;
17	>	import java.util.concurrent.CancellationException;
18	>	import java.util.concurrent.ExecutionException;
19	>	import java.util.concurrent.Executor;
20	>	import java.util.concurrent.ExecutorService;
21	>	import java.util.concurrent.Future;
22	>	import java.util.concurrent.RejectedExecutionException;
23	>	import java.util.concurrent.RunnableFuture;
24	>	import java.util.concurrent.TimeUnit;
25	>	import java.util.concurrent.TimeoutException;
26
27		/**
28	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
29	<	* ForkJoinTask is a thread-like entity that is much lighter weight
30	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
31	<	* hosted by a small number of actual threads in a ForkJoinPool,
32	<	* at the price of some usage limitations.
33	<	*
34	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
35	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
36	<	* set of restrictions (that are only partially statically
37	<	* enforceable) reflecting their intended use as computational tasks
38	<	* calculating pure functions or operating on purely isolated objects.
39	<	* The primary coordination mechanisms supported for ForkJoinTasks are
40	<	* <tt>fork</tt>, that arranges asynchronous execution, and
41	<	* <tt>join</tt>, that doesn't proceed until the task's result has
42	<	* been computed. (Cancellation is also supported).  The computation
43	<	* defined in the <tt>compute</tt> method should avoid
44	<	* <tt>synchronized</tt> methods or blocks, and should minimize
45	<	* blocking 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 external synchronization becomes
54	<	* exhausted. This usage restriction is in part enforced by not
55	<	* permitting checked exceptions such as IOExceptions to be
56	<	* 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.
61	<	*
62	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
63	<	* subclassed.  Instead, you subclass one of the abstract classes that
64	<	* support different styles of fork/join processing.  Normally, a
65	<	* concrete ForkJoinTask subclass declares fields comprising its
66	<	* parameters, established in a constructor, and then defines a
67	<	* <tt>compute</tt> method that somehow uses the control methods
68	<	* supplied by this base class. While these methods have
69	<	* <tt>public</tt> access, some of them may only be called from within
70	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
71	<	* result in exceptions or errors including ClassCastException.  The
72	<	* only way to invoke a "main" driver task is to submit it to a
73	<	* ForkJoinPool. Once started, this will usually in turn start other
74	<	* subtasks.
75	<	*
76	<	* <p>Most base support methods are <tt>final</tt> because their
77	<	* implementations are intrinsically tied to the underlying
78	<	* lightweight task scheduling framework, and so cannot be overridden.
79	<	* Developers creating new basic styles of fork/join processing should
80	<	* minimally implement protected methods <tt>exec</tt>,
81	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
82	<	* introducing an abstract computational method that can be
83	<	* implemented in its subclasses. To support such extensions,
84	<	* instances of ForkJoinTasks maintain an atomically updated
85	<	* <tt>short</tt> representing user-defined control state.  Control
86	<	* state is guaranteed initially to be zero, and to be negative upon
87	<	* completion, but may otherwise be used for any other control
88	<	* purposes, such as maintaining join counts.  The {@link
89	<	* ForkJoinWorkerThread} class supports additional inspection and
90	<	* tuning methods that can be useful when developing extensions.
28	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
29	>	* A {@code ForkJoinTask} is a thread-like entity that is much
30	>	* lighter weight than a normal thread.  Huge numbers of tasks and
31	>	* subtasks may be hosted by a small number of actual threads in a
32	>	* ForkJoinPool, at the price of some usage limitations.
33	>	*
34	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
35	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
36	>	* start other subtasks.  As indicated by the name of this class,
37	>	* many programs using {@code ForkJoinTask} employ only methods
38	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
39	>	* #invokeAll(ForkJoinTask...) invokeAll}.  However, this class also
40	>	* provides a number of other methods that can come into play in
41	>	* advanced usages, as well as extension mechanics that allow
42	>	* support of new forms of fork/join processing.
43	>	*
44	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
45	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
46	>	* restrictions (that are only partially statically enforceable)
47	>	* reflecting their intended use as computational tasks calculating
48	>	* pure functions or operating on purely isolated objects.  The
49	>	* primary coordination mechanisms are {@link #fork}, that arranges
50	>	* asynchronous execution, and {@link #join}, that doesn't proceed
51	>	* until the task's result has been computed.  Computations should
52	>	* avoid {@code synchronized} methods or blocks, and should minimize
53	>	* other blocking synchronization apart from joining other tasks or
54	>	* using synchronizers such as Phasers that are advertised to
55	>	* cooperate with fork/join scheduling. Tasks should also not perform
56	>	* blocking IO, and should ideally access variables that are
57	>	* completely independent of those accessed by other running
58	>	* tasks. Minor breaches of these restrictions, for example using
59	>	* shared output streams, may be tolerable in practice, but frequent
60	>	* use may result in poor performance, and the potential to
61	>	* indefinitely stall if the number of threads not waiting for IO or
62	>	* other external synchronization becomes exhausted. This usage
63	>	* restriction is in part enforced by not permitting checked
64	>	* exceptions such as {@code IOExceptions} to be thrown. However,
65	>	* computations may still encounter unchecked exceptions, that are
66	>	* rethrown to callers attempting to join them. These exceptions may
67	>	* additionally include {@link RejectedExecutionException} stemming
68	>	* from internal resource exhaustion, such as failure to allocate
69	>	* internal task queues.
70	>	*
71	>	* <p>The primary method for awaiting completion and extracting
72	>	* results of a task is {@link #join}, but there are several variants:
73	>	* The {@link Future#get} methods support interruptible and/or timed
74	>	* waits for completion and report results using {@code Future}
75	>	* conventions. Method {@link #invoke} is semantically
76	>	* equivalent to {@code fork(); join()} but always attempts to begin
77	>	* execution in the current thread. The "<em>quiet</em>" forms of
78	>	* these methods do not extract results or report exceptions. These
79	>	* may be useful when a set of tasks are being executed, and you need
80	>	* to delay processing of results or exceptions until all complete.
81	>	* Method {@code invokeAll} (available in multiple versions)
82	>	* performs the most common form of parallel invocation: forking a set
83	>	* of tasks and joining them all.
84	>	*
85	>	* <p>The execution status of tasks may be queried at several levels
86	>	* of detail: {@link #isDone} is true if a task completed in any way
87	>	* (including the case where a task was cancelled without executing);
88	>	* {@link #isCompletedNormally} is true if a task completed without
89	>	* cancellation or encountering an exception; {@link #isCancelled} is
90	>	* true if the task was cancelled (in which case {@link #getException}
91	>	* returns a {@link java.util.concurrent.CancellationException}); and
92	>	* {@link #isCompletedAbnormally} is true if a task was either
93	>	* cancelled or encountered an exception, in which case {@link
94	>	* #getException} will return either the encountered exception or
95	>	* {@link java.util.concurrent.CancellationException}.
96	>	*
97	>	* <p>The ForkJoinTask class is not usually directly subclassed.
98	>	* Instead, you subclass one of the abstract classes that support a
99	>	* particular style of fork/join processing, typically {@link
100	>	* RecursiveAction} for computations that do not return results, or
101	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
102	>	* ForkJoinTask subclass declares fields comprising its parameters,
103	>	* established in a constructor, and then defines a {@code compute}
104	>	* method that somehow uses the control methods supplied by this base
105	>	* class. While these methods have {@code public} access (to allow
106	>	* instances of different task subclasses to call each other's
107	>	* methods), some of them may only be called from within other
108	>	* ForkJoinTasks (as may be determined using method {@link
109	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
110	>	* result in exceptions or errors, possibly including
111	>	* {@code ClassCastException}.
112	>	*
113	>	* <p>Method {@link #join} and its variants are appropriate for use
114	>	* only when completion dependencies are acyclic; that is, the
115	>	* parallel computation can be described as a directed acyclic graph
116	>	* (DAG). Otherwise, executions may encounter a form of deadlock as
117	>	* tasks cyclically wait for each other.  However, this framework
118	>	* supports other methods and techniques (for example the use of
119	>	* {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
120	>	* may be of use in constructing custom subclasses for problems that
121	>	* are not statically structured as DAGs.
122	>	*
123	>	* <p>Most base support methods are {@code final}, to prevent
124	>	* overriding of implementations that are intrinsically tied to the
125	>	* underlying lightweight task scheduling framework.  Developers
126	>	* creating new basic styles of fork/join processing should minimally
127	>	* implement {@code protected} methods {@link #exec}, {@link
128	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
129	>	* an abstract computational method that can be implemented in its
130	>	* subclasses, possibly relying on other {@code protected} methods
131	>	* provided by this class.
132		*
133		* <p>ForkJoinTasks should perform relatively small amounts of
134	<	* computations, othewise splitting into smaller tasks. As a very
135	<	* rough rule of thumb, a task should perform more than 100 and less
136	<	* than 10000 basic computational steps. If tasks are too big, then
137	<	* parellelism cannot improve throughput. If too small, then memory
138	<	* and internal task maintenance overhead may overwhelm processing.
139	<	*
140	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
141	<	* be used in extensions such as remote execution frameworks. However,
142	<	* it is in general safe to serialize tasks only before or after, but
143	<	* not during execution. Serialization is not relied on during
144	<	* execution itself.
134	>	* computation. Large tasks should be split into smaller subtasks,
135	>	* usually via recursive decomposition. As a very rough rule of thumb,
136	>	* a task should perform more than 100 and less than 10000 basic
137	>	* computational steps, and should avoid indefinite looping. If tasks
138	>	* are too big, then parallelism cannot improve throughput. If too
139	>	* small, then memory and internal task maintenance overhead may
140	>	* overwhelm processing.
141	>	*
142	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
143	>	* and {@link Callable}, that may be of use when mixing execution of
144	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
145	>	* of this form, consider using a pool constructed in <em>asyncMode</em>.
146	>	*
147	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
148	>	* used in extensions such as remote execution frameworks. It is
149	>	* sensible to serialize tasks only before or after, but not during,
150	>	* execution. Serialization is not relied on during execution itself.
151	>	*
152	>	* @since 1.7
153	>	* @author Doug Lea
154		*/
155		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
156	<	/**
157	<	* Status field holding all run status. We pack this into a single
158	<	* int both to minimize footprint overhead and to ensure atomicity
159	<	* (updates are via CAS).
160	<	*
161	<	* Status is initially zero, and takes on nonnegative values until
162	<	* completed, upon which status holds COMPLETED. CANCELLED, or
163	<	* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
164	<	* blocking waits by other threads have SIGNAL_MASK bits set --
165	<	* bit 15 for external (nonFJ) waits, and the rest a count of
166	<	* waiting FJ threads.  (This representation relies on
167	<	* ForkJoinPool max thread limits). Completion of a stolen task
168	<	* with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
169	<	* though suboptimal for some purposes, we use basic builtin
170	<	* wait/notify to take advantage of "monitor inflation" in JVMs
171	<	* that we would otherwise need to emulate to avoid adding further
172	<	* per-task bookkeeping overhead. Note that bits 16-28 are
173	<	* currently unused. Also value 0x80000000 is available as spare
174	<	* completion value.
175	<	*/
176	<	volatile int status; // accessed directy by pool and workers
177	<
178	<	static final int COMPLETION_MASK      = 0xe0000000;
179	<	static final int NORMAL               = 0xe0000000; // == mask
180	<	static final int CANCELLED            = 0xc0000000;
181	<	static final int EXCEPTIONAL          = 0xa0000000;
182	<	static final int SIGNAL_MASK          = 0x0000ffff;
183	<	static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
184	<	static final int EXTERNAL_SIGNAL      = 0x00008000; // top bit of low word
156	>
157	>	/*
158	>	* See the internal documentation of class ForkJoinPool for a
159	>	* general implementation overview.  ForkJoinTasks are mainly
160	>	* responsible for maintaining their "status" field amidst relays
161	>	* to methods in ForkJoinWorkerThread and ForkJoinPool. The
162	>	* methods of this class are more-or-less layered into (1) basic
163	>	* status maintenance (2) execution and awaiting completion (3)
164	>	* user-level methods that additionally report results. This is
165	>	* sometimes hard to see because this file orders exported methods
166	>	* in a way that flows well in javadocs. In particular, most
167	>	* join mechanics are in method quietlyJoin, below.
168	>	*/
169	>
170	>	/*
171	>	* The status field holds run control status bits packed into a
172	>	* single int to minimize footprint and to ensure atomicity (via
173	>	* CAS).  Status is initially zero, and takes on nonnegative
174	>	* values until completed, upon which status holds value
175	>	* NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
176	>	* waits by other threads have the SIGNAL bit set.  Completion of
177	>	* a stolen task with SIGNAL set awakens any waiters via
178	>	* notifyAll. Even though suboptimal for some purposes, we use
179	>	* basic builtin wait/notify to take advantage of "monitor
180	>	* inflation" in JVMs that we would otherwise need to emulate to
181	>	* avoid adding further per-task bookkeeping overhead.  We want
182	>	* these monitors to be "fat", i.e., not use biasing or thin-lock
183	>	* techniques, so use some odd coding idioms that tend to avoid
184	>	* them.
185	>	*/
186	>
187	>	/** The run status of this task */
188	>	volatile int status; // accessed directly by pool and workers
189	>
190	>	private static final int NORMAL      = -1;
191	>	private static final int CANCELLED   = -2;
192	>	private static final int EXCEPTIONAL = -3;
193	>	private static final int SIGNAL      =  1;
194
195		/**
196		* Table of exceptions thrown by tasks, to enable reporting by
197		* callers. Because exceptions are rare, we don't directly keep
198	<	* them with task objects, but instead us a weak ref table.  Note
198	>	* them with task objects, but instead use a weak ref table.  Note
199		* that cancellation exceptions don't appear in the table, but are
200		* instead recorded as status values.
201	<	* Todo: Use ConcurrentReferenceHashMap
201	>	* TODO: Use ConcurrentReferenceHashMap
202		*/
203		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
204		Collections.synchronizedMap
205		(new WeakHashMap<ForkJoinTask<?>, Throwable>());
206
207	<	// within-package utilities
207	>	// Maintaining completion status
208
209		/**
210	<	* Get current worker thread, or null if not a worker thread
210	>	* Marks completion and wakes up threads waiting to join this task,
211	>	* also clearing signal request bits.
212	>	*
213	>	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
214		*/
215	<	static ForkJoinWorkerThread getWorker() {
216	<	Thread t = Thread.currentThread();
217	<	return ((t instanceof ForkJoinWorkerThread)?
218	<	(ForkJoinWorkerThread)t : null);
215	>	private void setCompletion(int completion) {
216	>	int s;
217	>	while ((s = status) >= 0) {
218	>	if (UNSAFE.compareAndSwapInt(this, statusOffset, s, completion)) {
219	>	if (s != 0)
220	>	synchronized (this) { notifyAll(); }
221	>	break;
222	>	}
223	>	}
224		}
225
226		/**
227	<	* Get pool of current worker thread, or null if not a worker thread
227	>	* Records exception and sets exceptional completion.
228	>	*
229	>	* @return status on exit
230		*/
231	<	static ForkJoinPool getWorkerPool() {
232	<	Thread t = Thread.currentThread();
233	<	return ((t instanceof ForkJoinWorkerThread)?
153	<	((ForkJoinWorkerThread)t).pool : null);
231	>	private void setExceptionalCompletion(Throwable rex) {
232	>	exceptionMap.put(this, rex);
233	>	setCompletion(EXCEPTIONAL);
234		}
235
236	<	final boolean casStatus(int cmp, int val) {
237	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
236	>	/**
237	>	* Blocks a worker thread until completed or timed out.  Called
238	>	* only by pool.
239	>	*/
240	>	final void internalAwaitDone(long millis, int nanos) {
241	>	if (status >= 0) {
242	>	try {     // the odd construction reduces lock bias effects
243	>	synchronized (this) {
244	>	if (status > 0 ||
245	>	UNSAFE.compareAndSwapInt(this, statusOffset,
246	>	0, SIGNAL))
247	>	wait(millis, nanos);
248	>	}
249	>	} catch (InterruptedException ie) {
250	>	cancelIfTerminating();
251	>	}
252	>	}
253		}
254
255		/**
256	<	* Workaround for not being able to rethrow unchecked exceptions.
256	>	* Blocks a non-worker-thread until completion.
257		*/
258	<	static void rethrowException(Throwable ex) {
259	<	if (ex != null)
260	<	_unsafe.throwException(ex);
258	>	private void externalAwaitDone() {
259	>	if (status >= 0) {
260	>	boolean interrupted = false;
261	>	synchronized(this) {
262	>	int s;
263	>	while ((s = status) >= 0) {
264	>	if (s == 0 &&
265	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
266	>	0, SIGNAL))
267	>	continue;
268	>	try {
269	>	wait();
270	>	} catch (InterruptedException ie) {
271	>	interrupted = true;
272	>	}
273	>	}
274	>	}
275	>	if (interrupted)
276	>	Thread.currentThread().interrupt();
277	>	}
278		}
279
168	–	// Setting completion status
169	–
280		/**
281	<	* Mark completion and wake up threads waiting to join this task.
172	<	* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
281	>	* Blocks a non-worker-thread until completion or interruption or timeout
282		*/
283	<	final void setCompletion(int completion) {
284	<	ForkJoinPool pool = getWorkerPool();
285	<	if (pool != null) {
286	<	int s; // Clear signal bits while setting completion status
287	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
288	<
289	<	if ((s & SIGNAL_MASK) != 0) {
290	<	if ((s &= INTERNAL_SIGNAL_MASK) != 0)
291	<	pool.updateRunningCount(s);
292	<	synchronized(this) { notifyAll(); }
283	>	private void externalInterruptibleAwaitDone(boolean timed, long nanos)
284	>	throws InterruptedException {
285	>	if (Thread.interrupted())
286	>	throw new InterruptedException();
287	>	if (status >= 0) {
288	>	long startTime = timed ? System.nanoTime() : 0L;
289	>	synchronized(this) {
290	>	int s;
291	>	while ((s = status) >= 0) {
292	>	long nt;
293	>	if (s == 0 &&
294	>	!UNSAFE.compareAndSwapInt(this, statusOffset,
295	>	0, SIGNAL))
296	>	continue;
297	>	else if (!timed)
298	>	wait();
299	>	else if ((nt = nanos - (System.nanoTime()-startTime)) > 0L)
300	>	wait(nt / 1000000, (int)(nt % 1000000));
301	>	else
302	>	break;
303	>	}
304		}
305		}
186	–	else
187	–	externallySetCompletion(completion);
306		}
307
308		/**
309	<	* Version of setCompletion for non-FJ threads.  Leaves signal
310	<	* bits for unblocked threads to adjust, and always notifies.
309	>	* Unless done, calls exec and records status if completed, but
310	>	* doesn't wait for completion otherwise. Primary execution method
311	>	* for ForkJoinWorkerThread.
312		*/
313	<	private void externallySetCompletion(int completion) {
314	<	int s;
315	<	do;while ((s = status) >= 0 &&
316	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
317	<	synchronized(this) { notifyAll(); }
313	>	final void quietlyExec() {
314	>	try {
315	>	if (status < 0 || !exec())
316	>	return;
317	>	} catch (Throwable rex) {
318	>	setExceptionalCompletion(rex);
319	>	return;
320	>	}
321	>	setCompletion(NORMAL); // must be outside try block
322		}
323
324	+	// public methods
325	+
326		/**
327	<	* Sets status to indicate normal completion
327	>	* Arranges to asynchronously execute this task.  While it is not
328	>	* necessarily enforced, it is a usage error to fork a task more
329	>	* than once unless it has completed and been reinitialized.
330	>	* Subsequent modifications to the state of this task or any data
331	>	* it operates on are not necessarily consistently observable by
332	>	* any thread other than the one executing it unless preceded by a
333	>	* call to {@link #join} or related methods, or a call to {@link
334	>	* #isDone} returning {@code true}.
335	>	*
336	>	* <p>This method may be invoked only from within {@code
337	>	* ForkJoinPool} computations (as may be determined using method
338	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
339	>	* result in exceptions or errors, possibly including {@code
340	>	* ClassCastException}.
341	>	*
342	>	* @return {@code this}, to simplify usage
343		*/
344	<	final void setNormalCompletion() {
345	<	// Try typical fast case -- single CAS, no signal, not already done.
346	<	// Manually expand casStatus to improve chances of inlining it
347	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
208	<	setCompletion(NORMAL);
344	>	public final ForkJoinTask<V> fork() {
345	>	((ForkJoinWorkerThread) Thread.currentThread())
346	>	.pushTask(this);
347	>	return this;
348		}
349
211	–	// internal waiting and notification
212	–
350		/**
351	<	* Performs the actual monitor wait for awaitDone
351	>	* Returns the result of the computation when it {@link #isDone is
352	>	* done}.  This method differs from {@link #get()} in that
353	>	* abnormal completion results in {@code RuntimeException} or
354	>	* {@code Error}, not {@code ExecutionException}, and that
355	>	* interrupts of the calling thread do <em>not</em> cause the
356	>	* method to abruptly return by throwing {@code
357	>	* InterruptedException}.
358	>	*
359	>	* @return the computed result
360		*/
361	<	private void doAwaitDone() {
362	<	// Minimize lock bias and in/de-flation effects by maximizing
363	<	// chances of waiting inside sync
364	<	try {
365	<	while (status >= 0)
366	<	synchronized(this) { if (status >= 0) wait(); }
222	<	} catch (InterruptedException ie) {
223	<	onInterruptedWait();
224	<	}
361	>	public final V join() {
362	>	quietlyJoin();
363	>	Throwable ex;
364	>	if (status < NORMAL && (ex = getException()) != null)
365	>	UNSAFE.throwException(ex);
366	>	return getRawResult();
367		}
368
369		/**
370	<	* Performs the actual monitor wait for awaitDone
370	>	* Commences performing this task, awaits its completion if
371	>	* necessary, and returns its result, or throws an (unchecked)
372	>	* {@code RuntimeException} or {@code Error} if the underlying
373	>	* computation did so.
374	>	*
375	>	* @return the computed result
376		*/
377	<	private void doAwaitDone(long startTime, long nanos) {
378	<	synchronized(this) {
379	<	try {
380	<	while (status >= 0) {
381	<	long nt = nanos - System.nanoTime() - startTime;
382	<	if (nt <= 0)
236	<	break;
237	<	wait(nt / 1000000, (int)(nt % 1000000));
238	<	}
239	<	} catch (InterruptedException ie) {
240	<	onInterruptedWait();
241	<	}
242	<	}
377	>	public final V invoke() {
378	>	quietlyInvoke();
379	>	Throwable ex;
380	>	if (status < NORMAL && (ex = getException()) != null)
381	>	UNSAFE.throwException(ex);
382	>	return getRawResult();
383		}
384
385	<	// Awaiting completion
385	>	/**
386	>	* Forks the given tasks, returning when {@code isDone} holds for
387	>	* each task or an (unchecked) exception is encountered, in which
388	>	* case the exception is rethrown. If more than one task
389	>	* encounters an exception, then this method throws any one of
390	>	* these exceptions. If any task encounters an exception, the
391	>	* other may be cancelled. However, the execution status of
392	>	* individual tasks is not guaranteed upon exceptional return. The
393	>	* status of each task may be obtained using {@link
394	>	* #getException()} and related methods to check if they have been
395	>	* cancelled, completed normally or exceptionally, or left
396	>	* unprocessed.
397	>	*
398	>	* <p>This method may be invoked only from within {@code
399	>	* ForkJoinPool} computations (as may be determined using method
400	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
401	>	* result in exceptions or errors, possibly including {@code
402	>	* ClassCastException}.
403	>	*
404	>	* @param t1 the first task
405	>	* @param t2 the second task
406	>	* @throws NullPointerException if any task is null
407	>	*/
408	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
409	>	t2.fork();
410	>	t1.invoke();
411	>	t2.join();
412	>	}
413
414		/**
415	<	* Sets status to indicate there is joiner, then waits for join,
416	<	* surrounded with pool notifications.
417	<	* @return status upon exit
415	>	* Forks the given tasks, returning when {@code isDone} holds for
416	>	* each task or an (unchecked) exception is encountered, in which
417	>	* case the exception is rethrown. If more than one task
418	>	* encounters an exception, then this method throws any one of
419	>	* these exceptions. If any task encounters an exception, others
420	>	* may be cancelled. However, the execution status of individual
421	>	* tasks is not guaranteed upon exceptional return. The status of
422	>	* each task may be obtained using {@link #getException()} and
423	>	* related methods to check if they have been cancelled, completed
424	>	* normally or exceptionally, or left unprocessed.
425	>	*
426	>	* <p>This method may be invoked only from within {@code
427	>	* ForkJoinPool} computations (as may be determined using method
428	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
429	>	* result in exceptions or errors, possibly including {@code
430	>	* ClassCastException}.
431	>	*
432	>	* @param tasks the tasks
433	>	* @throws NullPointerException if any task is null
434		*/
435	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
436	<	ForkJoinPool pool = w == null? null : w.pool;
437	<	int s;
438	<	while ((s = status) >= 0) {
439	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
440	<	if (pool == null || !pool.preJoin(this, maintainParallelism))
441	<	doAwaitDone();
442	<	if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
443	<	adjustPoolCountsOnUnblock(pool);
444	<	break;
435	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
436	>	Throwable ex = null;
437	>	int last = tasks.length - 1;
438	>	for (int i = last; i >= 0; --i) {
439	>	ForkJoinTask<?> t = tasks[i];
440	>	if (t == null) {
441	>	if (ex == null)
442	>	ex = new NullPointerException();
443	>	}
444	>	else if (i != 0)
445	>	t.fork();
446	>	else {
447	>	t.quietlyInvoke();
448	>	if (ex == null && t.status < NORMAL)
449	>	ex = t.getException();
450		}
451		}
452	<	return s;
452	>	for (int i = 1; i <= last; ++i) {
453	>	ForkJoinTask<?> t = tasks[i];
454	>	if (t != null) {
455	>	if (ex != null)
456	>	t.cancel(false);
457	>	else {
458	>	t.quietlyJoin();
459	>	if (ex == null && t.status < NORMAL)
460	>	ex = t.getException();
461	>	}
462	>	}
463	>	}
464	>	if (ex != null)
465	>	UNSAFE.throwException(ex);
466		}
467
468		/**
469	<	* Timed version of awaitDone
470	<	* @return status upon exit
469	>	* Forks all tasks in the specified collection, returning when
470	>	* {@code isDone} holds for each task or an (unchecked) exception
471	>	* is encountered, in which case the exception is rethrown. If
472	>	* more than one task encounters an exception, then this method
473	>	* throws any one of these exceptions. If any task encounters an
474	>	* exception, others may be cancelled. However, the execution
475	>	* status of individual tasks is not guaranteed upon exceptional
476	>	* return. The status of each task may be obtained using {@link
477	>	* #getException()} and related methods to check if they have been
478	>	* cancelled, completed normally or exceptionally, or left
479	>	* unprocessed.
480	>	*
481	>	* <p>This method may be invoked only from within {@code
482	>	* ForkJoinPool} computations (as may be determined using method
483	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
484	>	* result in exceptions or errors, possibly including {@code
485	>	* ClassCastException}.
486	>	*
487	>	* @param tasks the collection of tasks
488	>	* @return the tasks argument, to simplify usage
489	>	* @throws NullPointerException if tasks or any element are null
490		*/
491	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
492	<	ForkJoinPool pool = w == null? null : w.pool;
493	<	int s;
494	<	while ((s = status) >= 0) {
495	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
496	<	long startTime = System.nanoTime();
497	<	if (pool == null || !pool.preJoin(this, false))
498	<	doAwaitDone(startTime, nanos);
499	<	if ((s = status) >= 0) {
500	<	adjustPoolCountsOnCancelledWait(pool);
501	<	s = status;
491	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
492	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
493	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
494	>	return tasks;
495	>	}
496	>	@SuppressWarnings("unchecked")
497	>	List<? extends ForkJoinTask<?>> ts =
498	>	(List<? extends ForkJoinTask<?>>) tasks;
499	>	Throwable ex = null;
500	>	int last = ts.size() - 1;
501	>	for (int i = last; i >= 0; --i) {
502	>	ForkJoinTask<?> t = ts.get(i);
503	>	if (t == null) {
504	>	if (ex == null)
505	>	ex = new NullPointerException();
506	>	}
507	>	else if (i != 0)
508	>	t.fork();
509	>	else {
510	>	t.quietlyInvoke();
511	>	if (ex == null && t.status < NORMAL)
512	>	ex = t.getException();
513	>	}
514	>	}
515	>	for (int i = 1; i <= last; ++i) {
516	>	ForkJoinTask<?> t = ts.get(i);
517	>	if (t != null) {
518	>	if (ex != null)
519	>	t.cancel(false);
520	>	else {
521	>	t.quietlyJoin();
522	>	if (ex == null && t.status < NORMAL)
523	>	ex = t.getException();
524		}
283	–	if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
284	–	adjustPoolCountsOnUnblock(pool);
285	–	break;
525		}
526		}
527	<	return s;
527	>	if (ex != null)
528	>	UNSAFE.throwException(ex);
529	>	return tasks;
530		}
531
532		/**
533	<	* Notify pool that thread is unblocked. Called by signalled
534	<	* threads when woken by non-FJ threads (which is atypical).
533	>	* Attempts to cancel execution of this task. This attempt will
534	>	* fail if the task has already completed or could not be
535	>	* cancelled for some other reason. If successful, and this task
536	>	* has not started when {@code cancel} is called, execution of
537	>	* this task is suppressed. After this method returns
538	>	* successfully, unless there is an intervening call to {@link
539	>	* #reinitialize}, subsequent calls to {@link #isCancelled},
540	>	* {@link #isDone}, and {@code cancel} will return {@code true}
541	>	* and calls to {@link #join} and related methods will result in
542	>	* {@code CancellationException}.
543	>	*
544	>	* <p>This method may be overridden in subclasses, but if so, must
545	>	* still ensure that these properties hold. In particular, the
546	>	* {@code cancel} method itself must not throw exceptions.
547	>	*
548	>	* <p>This method is designed to be invoked by <em>other</em>
549	>	* tasks. To terminate the current task, you can just return or
550	>	* throw an unchecked exception from its computation method, or
551	>	* invoke {@link #completeExceptionally}.
552	>	*
553	>	* @param mayInterruptIfRunning this value has no effect in the
554	>	* default implementation because interrupts are not used to
555	>	* control cancellation.
556	>	*
557	>	* @return {@code true} if this task is now cancelled
558		*/
559	<	private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
560	<	int s;
561	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
298	<	if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
299	<	pool.updateRunningCount(s);
559	>	public boolean cancel(boolean mayInterruptIfRunning) {
560	>	setCompletion(CANCELLED);
561	>	return status == CANCELLED;
562		}
563
564		/**
565	<	* Notify pool to adjust counts on cancelled or timed out wait
565	>	* Cancels, ignoring any exceptions thrown by cancel. Used during
566	>	* worker and pool shutdown. Cancel is spec'ed not to throw any
567	>	* exceptions, but if it does anyway, we have no recourse during
568	>	* shutdown, so guard against this case.
569		*/
570	<	private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
571	<	if (pool != null) {
572	<	int s;
573	<	while ((s = status) >= 0 && (s & INTERNAL_SIGNAL_MASK) != 0) {
309	<	if (casStatus(s, s - 1)) {
310	<	pool.updateRunningCount(1);
311	<	break;
312	<	}
313	<	}
570	>	final void cancelIgnoringExceptions() {
571	>	try {
572	>	cancel(false);
573	>	} catch (Throwable ignore) {
574		}
575		}
576
577	<	private void onInterruptedWait() {
577	>	/**
578	>	* Cancels if current thread is a terminating worker thread,
579	>	* ignoring any exceptions thrown by cancel.
580	>	*/
581	>	final void cancelIfTerminating() {
582		Thread t = Thread.currentThread();
583	<	if (t instanceof ForkJoinWorkerThread) {
584	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
321	<	if (w.isTerminating())
322	<	cancelIgnoreExceptions();
323	<	}
324	<	else { // re-interrupt
583	>	if ((t instanceof ForkJoinWorkerThread) &&
584	>	((ForkJoinWorkerThread) t).isTerminating()) {
585		try {
586	<	t.interrupt();
587	<	} catch (SecurityException ignore) {
586	>	cancel(false);
587	>	} catch (Throwable ignore) {
588		}
589		}
590		}
591
592	<	// Recording and reporting exceptions
593	<
334	<	private void setDoneExceptionally(Throwable rex) {
335	<	exceptionMap.put(this, rex);
336	<	setCompletion(EXCEPTIONAL);
592	>	public final boolean isDone() {
593	>	return status < 0;
594		}
595
596	<	/**
597	<	* Throws the exception associated with status s;
341	<	* @throws the exception
342	<	*/
343	<	private void reportException(int s) {
344	<	if ((s &= COMPLETION_MASK) < NORMAL) {
345	<	if (s == CANCELLED)
346	<	throw new CancellationException();
347	<	else
348	<	rethrowException(exceptionMap.get(this));
349	<	}
596	>	public final boolean isCancelled() {
597	>	return status == CANCELLED;
598		}
599
600		/**
601	<	* Returns result or throws exception using j.u.c.Future conventions
602	<	* Only call when isDone known to be true.
601	>	* Returns {@code true} if this task threw an exception or was cancelled.
602	>	*
603	>	* @return {@code true} if this task threw an exception or was cancelled
604		*/
605	<	private V reportFutureResult()
606	<	throws ExecutionException, InterruptedException {
358	<	int s = status & COMPLETION_MASK;
359	<	if (s < NORMAL) {
360	<	Throwable ex;
361	<	if (s == CANCELLED)
362	<	throw new CancellationException();
363	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
364	<	throw new ExecutionException(ex);
365	<	if (Thread.interrupted())
366	<	throw new InterruptedException();
367	<	}
368	<	return getRawResult();
605	>	public final boolean isCompletedAbnormally() {
606	>	return status < NORMAL;
607		}
608
609		/**
610	<	* Returns result or throws exception using j.u.c.Future conventions
611	<	* with timeouts
610	>	* Returns {@code true} if this task completed without throwing an
611	>	* exception and was not cancelled.
612	>	*
613	>	* @return {@code true} if this task completed without throwing an
614	>	* exception and was not cancelled
615		*/
616	<	private V reportTimedFutureResult()
617	<	throws InterruptedException, ExecutionException, TimeoutException {
377	<	Throwable ex;
378	<	int s = status & COMPLETION_MASK;
379	<	if (s == NORMAL)
380	<	return getRawResult();
381	<	if (s == CANCELLED)
382	<	throw new CancellationException();
383	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
384	<	throw new ExecutionException(ex);
385	<	if (Thread.interrupted())
386	<	throw new InterruptedException();
387	<	throw new TimeoutException();
616	>	public final boolean isCompletedNormally() {
617	>	return status == NORMAL;
618		}
619
390	–	// internal execution methods
391	–
620		/**
621	<	* Calls exec, recording completion, and rethrowing exception if
622	<	* encountered. Caller should normally check status before calling
623	<	* @return true if completed normally
621	>	* Returns the exception thrown by the base computation, or a
622	>	* {@code CancellationException} if cancelled, or {@code null} if
623	>	* none or if the method has not yet completed.
624	>	*
625	>	* @return the exception, or {@code null} if none
626		*/
627	<	private boolean tryExec() {
628	<	try { // try block must contain only call to exec
629	<	if (!exec())
630	<	return false;
631	<	} catch (Throwable rex) {
402	<	setDoneExceptionally(rex);
403	<	rethrowException(rex);
404	<	return false; // not reached
405	<	}
406	<	setNormalCompletion();
407	<	return true;
627	>	public final Throwable getException() {
628	>	int s = status;
629	>	return ((s >= NORMAL)    ? null :
630	>	(s == CANCELLED) ? new CancellationException() :
631	>	exceptionMap.get(this));
632		}
633
634		/**
635	<	* Main execution method used by worker threads. Invokes
636	<	* base computation unless already complete
635	>	* Completes this task abnormally, and if not already aborted or
636	>	* cancelled, causes it to throw the given exception upon
637	>	* {@code join} and related operations. This method may be used
638	>	* to induce exceptions in asynchronous tasks, or to force
639	>	* completion of tasks that would not otherwise complete.  Its use
640	>	* in other situations is discouraged.  This method is
641	>	* overridable, but overridden versions must invoke {@code super}
642	>	* implementation to maintain guarantees.
643	>	*
644	>	* @param ex the exception to throw. If this exception is not a
645	>	* {@code RuntimeException} or {@code Error}, the actual exception
646	>	* thrown will be a {@code RuntimeException} with cause {@code ex}.
647		*/
648	<	final void quietlyExec() {
649	<	if (status >= 0) {
650	<	try {
651	<	if (!exec())
418	<	return;
419	<	} catch(Throwable rex) {
420	<	setDoneExceptionally(rex);
421	<	return;
422	<	}
423	<	setNormalCompletion();
424	<	}
648	>	public void completeExceptionally(Throwable ex) {
649	>	setExceptionalCompletion((ex instanceof RuntimeException) ||
650	>	(ex instanceof Error) ? ex :
651	>	new RuntimeException(ex));
652		}
653
654		/**
655	<	* Calls exec, recording but not rethrowing exception
656	<	* Caller should normally check status before calling
657	<	* @return true if completed normally
655	>	* Completes this task, and if not already aborted or cancelled,
656	>	* returning the given value as the result of subsequent
657	>	* invocations of {@code join} and related operations. This method
658	>	* may be used to provide results for asynchronous tasks, or to
659	>	* provide alternative handling for tasks that would not otherwise
660	>	* complete normally. Its use in other situations is
661	>	* discouraged. This method is overridable, but overridden
662	>	* versions must invoke {@code super} implementation to maintain
663	>	* guarantees.
664	>	*
665	>	* @param value the result value for this task
666		*/
667	<	private boolean tryQuietlyInvoke() {
667	>	public void complete(V value) {
668		try {
669	<	if (!exec())
435	<	return false;
669	>	setRawResult(value);
670		} catch (Throwable rex) {
671	<	setDoneExceptionally(rex);
672	<	return false;
439	<	}
440	<	setNormalCompletion();
441	<	return true;
442	<	}
443	<
444	<	/**
445	<	* Cancel, ignoring any exceptions it throws
446	<	*/
447	<	final void cancelIgnoreExceptions() {
448	<	try {
449	<	cancel(false);
450	<	} catch(Throwable ignore) {
671	>	setExceptionalCompletion(rex);
672	>	return;
673		}
674	<	}
453	<
454	<	// public methods
455	<
456	<	/**
457	<	* Arranges to asynchronously execute this task.  While it is not
458	<	* necessarily enforced, it is a usage error to fork a task more
459	<	* than once unless it has completed and been reinitialized.  This
460	<	* method may be invoked only from within other ForkJoinTask
461	<	* computations. Attempts to invoke in other contexts result in
462	<	* exceptions or errors including ClassCastException.
463	<	*/
464	<	public final void fork() {
465	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
674	>	setCompletion(NORMAL);
675		}
676
677		/**
678	<	* Returns the result of the computation when it is ready.
679	<	* This method differs from <tt>get</tt> in that abnormal
471	<	* completion results in RuntimeExceptions or Errors, not
472	<	* ExecutionExceptions.
678	>	* Waits if necessary for the computation to complete, and then
679	>	* retrieves its result.
680		*
681		* @return the computed result
682	+	* @throws CancellationException if the computation was cancelled
683	+	* @throws ExecutionException if the computation threw an
684	+	* exception
685	+	* @throws InterruptedException if the current thread is not a
686	+	* member of a ForkJoinPool and was interrupted while waiting
687		*/
476	–	public final V join() {
477	–	ForkJoinWorkerThread w = getWorker();
478	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryExec())
479	–	reportException(awaitDone(w, true));
480	–	return getRawResult();
481	–	}
482	–
688		public final V get() throws InterruptedException, ExecutionException {
689	<	ForkJoinWorkerThread w = getWorker();
690	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
691	<	awaitDone(w, true);
692	<	return reportFutureResult();
693	<	}
694	<
695	<	public final V get(long timeout, TimeUnit unit)
696	<	throws InterruptedException, ExecutionException, TimeoutException {
697	<	ForkJoinWorkerThread w = getWorker();
698	<	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
699	<	awaitDone(w, unit.toNanos(timeout));
700	<	return reportTimedFutureResult();
701	<	}
497	<
498	<	/**
499	<	* Possibly executes other tasks until this task is ready, then
500	<	* returns the result of the computation.  This method may be more
501	<	* efficient than <tt>join</tt>, but is only applicable when there
502	<	* are no potemtial dependencies between continuation of the
503	<	* current task and that of any other task that might be executed
504	<	* while helping. (This usually holds for pure divide-and-conquer
505	<	* tasks).
506	<	* @return the computed result
507	<	*/
508	<	public final V helpJoin() {
509	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
510	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
511	<	reportException(w.helpJoinTask(this));
689	>	Thread t = Thread.currentThread();
690	>	if (t instanceof ForkJoinWorkerThread)
691	>	quietlyJoin();
692	>	else
693	>	externalInterruptibleAwaitDone(false, 0L);
694	>	int s = status;
695	>	if (s != NORMAL) {
696	>	Throwable ex;
697	>	if (s == CANCELLED)
698	>	throw new CancellationException();
699	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
700	>	throw new ExecutionException(ex);
701	>	}
702		return getRawResult();
703		}
704
705		/**
706	<	* Performs this task, awaits its completion if necessary, and
707	<	* return its result.
708	<	* @throws Throwable (a RuntimeException, Error, or unchecked
709	<	* exception) if the underlying computation did so.
706	>	* Waits if necessary for at most the given time for the computation
707	>	* to complete, and then retrieves its result, if available.
708	>	*
709	>	* @param timeout the maximum time to wait
710	>	* @param unit the time unit of the timeout argument
711		* @return the computed result
712	+	* @throws CancellationException if the computation was cancelled
713	+	* @throws ExecutionException if the computation threw an
714	+	* exception
715	+	* @throws InterruptedException if the current thread is not a
716	+	* member of a ForkJoinPool and was interrupted while waiting
717	+	* @throws TimeoutException if the wait timed out
718		*/
719	<	public final V invoke() {
720	<	if (status >= 0 && tryExec())
721	<	return getRawResult();
719	>	public final V get(long timeout, TimeUnit unit)
720	>	throws InterruptedException, ExecutionException, TimeoutException {
721	>	long nanos = unit.toNanos(timeout);
722	>	Thread t = Thread.currentThread();
723	>	if (t instanceof ForkJoinWorkerThread)
724	>	((ForkJoinWorkerThread)t).joinTask(this, true, nanos);
725		else
726	<	return join();
726	>	externalInterruptibleAwaitDone(true, nanos);
727	>	int s = status;
728	>	if (s != NORMAL) {
729	>	Throwable ex;
730	>	if (s == CANCELLED)
731	>	throw new CancellationException();
732	>	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
733	>	throw new ExecutionException(ex);
734	>	throw new TimeoutException();
735	>	}
736	>	return getRawResult();
737		}
738
739		/**
740	<	* Joins this task, without returning its result or throwing an
740	>	* Joins this task, without returning its result or throwing its
741		* exception. This method may be useful when processing
742		* collections of tasks when some have been cancelled or otherwise
743		* known to have aborted.
744		*/
745		public final void quietlyJoin() {
746	<	if (status >= 0) {
747	<	ForkJoinWorkerThread w = getWorker();
748	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
749	<	awaitDone(w, true);
746	>	Thread t;
747	>	if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) {
748	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) t;
749	>	if (status >= 0) {
750	>	if (w.unpushTask(this)) {
751	>	boolean completed;
752	>	try {
753	>	completed = exec();
754	>	} catch (Throwable rex) {
755	>	setExceptionalCompletion(rex);
756	>	return;
757	>	}
758	>	if (completed) {
759	>	setCompletion(NORMAL);
760	>	return;
761	>	}
762	>	}
763	>	w.joinTask(this, false, 0L);
764	>	}
765		}
766	+	else
767	+	externalAwaitDone();
768		}
769
770		/**
771	<	* Possibly executes other tasks until this task is ready.
771	>	* Commences performing this task and awaits its completion if
772	>	* necessary, without returning its result or throwing its
773	>	* exception.
774		*/
775	<	public final void quietlyHelpJoin() {
775	>	public final void quietlyInvoke() {
776		if (status >= 0) {
777	<	ForkJoinWorkerThread w =
778	<	(ForkJoinWorkerThread)(Thread.currentThread());
779	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
780	<	w.helpJoinTask(this);
777	>	boolean completed;
778	>	try {
779	>	completed = exec();
780	>	} catch (Throwable rex) {
781	>	setExceptionalCompletion(rex);
782	>	return;
783	>	}
784	>	if (completed)
785	>	setCompletion(NORMAL);
786	>	else
787	>	quietlyJoin();
788		}
789		}
790
791		/**
792	<	* Performs this task and awaits its completion if necessary,
793	<	* without returning its result or throwing an exception. This
794	<	* method may be useful when processing collections of tasks when
795	<	* some have been cancelled or otherwise known to have aborted.
792	>	* Possibly executes tasks until the pool hosting the current task
793	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
794	>	* be of use in designs in which many tasks are forked, but none
795	>	* are explicitly joined, instead executing them until all are
796	>	* processed.
797	>	*
798	>	* <p>This method may be invoked only from within {@code
799	>	* ForkJoinPool} computations (as may be determined using method
800	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
801	>	* result in exceptions or errors, possibly including {@code
802	>	* ClassCastException}.
803		*/
804	<	public final void quietlyInvoke() {
805	<	if (status >= 0 && !tryQuietlyInvoke())
806	<	quietlyJoin();
804	>	public static void helpQuiesce() {
805	>	((ForkJoinWorkerThread) Thread.currentThread())
806	>	.helpQuiescePool();
807		}
808
809		/**
810	<	* Returns true if the computation performed by this task has
811	<	* completed (or has been cancelled).
812	<	* @return true if this computation has completed
810	>	* Resets the internal bookkeeping state of this task, allowing a
811	>	* subsequent {@code fork}. This method allows repeated reuse of
812	>	* this task, but only if reuse occurs when this task has either
813	>	* never been forked, or has been forked, then completed and all
814	>	* outstanding joins of this task have also completed. Effects
815	>	* under any other usage conditions are not guaranteed.
816	>	* This method may be useful when executing
817	>	* pre-constructed trees of subtasks in loops.
818	>	*
819	>	* <p>Upon completion of this method, {@code isDone()} reports
820	>	* {@code false}, and {@code getException()} reports {@code
821	>	* null}. However, the value returned by {@code getRawResult} is
822	>	* unaffected. To clear this value, you can invoke {@code
823	>	* setRawResult(null)}.
824		*/
825	<	public final boolean isDone() {
826	<	return status < 0;
825	>	public void reinitialize() {
826	>	if (status == EXCEPTIONAL)
827	>	exceptionMap.remove(this);
828	>	status = 0;
829		}
830
831		/**
832	<	* Returns true if this task was cancelled.
833	<	* @return true if this task was cancelled
832	>	* Returns the pool hosting the current task execution, or null
833	>	* if this task is executing outside of any ForkJoinPool.
834	>	*
835	>	* @see #inForkJoinPool
836	>	* @return the pool, or {@code null} if none
837		*/
838	<	public final boolean isCancelled() {
839	<	return (status & COMPLETION_MASK) == CANCELLED;
838	>	public static ForkJoinPool getPool() {
839	>	Thread t = Thread.currentThread();
840	>	return (t instanceof ForkJoinWorkerThread) ?
841	>	((ForkJoinWorkerThread) t).pool : null;
842		}
843
844		/**
845	<	* Returns true if this task threw an exception or was cancelled
846	<	* @return true if this task threw an exception or was cancelled
845	>	* Returns {@code true} if the current thread is executing as a
846	>	* ForkJoinPool computation.
847	>	*
848	>	* @return {@code true} if the current thread is executing as a
849	>	* ForkJoinPool computation, or false otherwise
850		*/
851	<	public final boolean completedAbnormally() {
852	<	return (status & COMPLETION_MASK) < NORMAL;
851	>	public static boolean inForkJoinPool() {
852	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
853		}
854
855		/**
856	<	* Returns the exception thrown by the base computation, or a
857	<	* CancellationException if cancelled, or null if none or if the
858	<	* method has not yet completed.
859	<	* @return the exception, or null if none
856	>	* Tries to unschedule this task for execution. This method will
857	>	* typically succeed if this task is the most recently forked task
858	>	* by the current thread, and has not commenced executing in
859	>	* another thread.  This method may be useful when arranging
860	>	* alternative local processing of tasks that could have been, but
861	>	* were not, stolen.
862	>	*
863	>	* <p>This method may be invoked only from within {@code
864	>	* ForkJoinPool} computations (as may be determined using method
865	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
866	>	* result in exceptions or errors, possibly including {@code
867	>	* ClassCastException}.
868	>	*
869	>	* @return {@code true} if unforked
870		*/
871	<	public final Throwable getException() {
872	<	int s = status & COMPLETION_MASK;
873	<	if (s >= NORMAL)
600	<	return null;
601	<	if (s == CANCELLED)
602	<	return new CancellationException();
603	<	return exceptionMap.get(this);
871	>	public boolean tryUnfork() {
872	>	return ((ForkJoinWorkerThread) Thread.currentThread())
873	>	.unpushTask(this);
874		}
875
876		/**
877	<	* Asserts that the results of this task's computation will not be
878	<	* used. If a cancellation occurs before this task is processed,
879	<	* then its <tt>compute</tt> method will not be executed,
880	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
611	<	* result in a CancellationException being thrown. Otherwise, when
612	<	* cancellation races with completion, there are no guarantees
613	<	* about whether <tt>isCancelled</tt> will report true, whether
614	<	* <tt>join</tt> will return normally or via an exception, or
615	<	* whether these behaviors will remain consistent upon repeated
616	<	* invocation.
877	>	* Returns an estimate of the number of tasks that have been
878	>	* forked by the current worker thread but not yet executed. This
879	>	* value may be useful for heuristic decisions about whether to
880	>	* fork other tasks.
881		*
882	<	* <p>This method may be overridden in subclasses, but if so, must
883	<	* still ensure that these minimal properties hold. In particular,
884	<	* the cancel method itself must not throw exceptions.
882	>	* <p>This method may be invoked only from within {@code
883	>	* ForkJoinPool} computations (as may be determined using method
884	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
885	>	* result in exceptions or errors, possibly including {@code
886	>	* ClassCastException}.
887		*
888	<	* <p> This method is designed to be invoked by <em>other</em>
889	<	* tasks. To terminate the current task, you can just return or
890	<	* throw an unchecked exception from its computation method, or
891	<	* invoke <tt>completeExceptionally(someException)</tt>.
888	>	* @return the number of tasks
889	>	*/
890	>	public static int getQueuedTaskCount() {
891	>	return ((ForkJoinWorkerThread) Thread.currentThread())
892	>	.getQueueSize();
893	>	}
894	>
895	>	/**
896	>	* Returns an estimate of how many more locally queued tasks are
897	>	* held by the current worker thread than there are other worker
898	>	* threads that might steal them.  This value may be useful for
899	>	* heuristic decisions about whether to fork other tasks. In many
900	>	* usages of ForkJoinTasks, at steady state, each worker should
901	>	* aim to maintain a small constant surplus (for example, 3) of
902	>	* tasks, and to process computations locally if this threshold is
903	>	* exceeded.
904		*
905	<	* @param mayInterruptIfRunning this value is ignored in the
906	<	* default implementation because tasks are not in general
907	<	* cancelled via interruption.
905	>	* <p>This method may be invoked only from within {@code
906	>	* ForkJoinPool} computations (as may be determined using method
907	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
908	>	* result in exceptions or errors, possibly including {@code
909	>	* ClassCastException}.
910		*
911	<	* @return true if this task is now cancelled
911	>	* @return the surplus number of tasks, which may be negative
912		*/
913	<	public boolean cancel(boolean mayInterruptIfRunning) {
914	<	setCompletion(CANCELLED);
915	<	return (status & COMPLETION_MASK) == CANCELLED;
913	>	public static int getSurplusQueuedTaskCount() {
914	>	return ((ForkJoinWorkerThread) Thread.currentThread())
915	>	.getEstimatedSurplusTaskCount();
916		}
917
918	+	// Extension methods
919	+
920		/**
921	<	* Completes this task abnormally, and if not already aborted or
922	<	* cancelled, causes it to throw the given exception upon
923	<	* <tt>join</tt> and related operations. This method may be used
924	<	* to induce exceptions in asynchronous tasks, or to force
925	<	* completion of tasks that would not otherwise complete.  This
926	<	* method is overridable, but overridden versions must invoke
927	<	* <tt>super</tt> implementation to maintain guarantees.
646	<	* @param ex the exception to throw. If this exception is
647	<	* not a RuntimeException or Error, the actual exception thrown
648	<	* will be a RuntimeException with cause ex.
921	>	* Returns the result that would be returned by {@link #join}, even
922	>	* if this task completed abnormally, or {@code null} if this task
923	>	* is not known to have been completed.  This method is designed
924	>	* to aid debugging, as well as to support extensions. Its use in
925	>	* any other context is discouraged.
926	>	*
927	>	* @return the result, or {@code null} if not completed
928		*/
929	<	public void completeExceptionally(Throwable ex) {
651	<	setDoneExceptionally((ex instanceof RuntimeException) ||
652	<	(ex instanceof Error)? ex :
653	<	new RuntimeException(ex));
654	<	}
929	>	public abstract V getRawResult();
930
931		/**
932	<	* Completes this task, and if not already aborted or cancelled,
933	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
934	<	* operations. This method may be used to provide results for
660	<	* asynchronous tasks, or to provide alternative handling for
661	<	* tasks that would not otherwise complete normally.
932	>	* Forces the given value to be returned as a result.  This method
933	>	* is designed to support extensions, and should not in general be
934	>	* called otherwise.
935		*
936	<	* @param value the result value for this task.
936	>	* @param value the value
937		*/
938	<	public void complete(V value) {
666	<	try {
667	<	setRawResult(value);
668	<	} catch(Throwable rex) {
669	<	setDoneExceptionally(rex);
670	<	return;
671	<	}
672	<	setNormalCompletion();
673	<	}
938	>	protected abstract void setRawResult(V value);
939
940		/**
941	<	* Resets the internal bookkeeping state of this task, allowing a
942	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
943	<	* this task, but only if reuse occurs when this task has either
944	<	* never been forked, or has been forked, then completed and all
945	<	* outstanding joins of this task have also completed. Effects
946	<	* under any other usage conditions are not guaranteed, and are
947	<	* almost surely wrong. This method may be useful when executing
948	<	* pre-constructed trees of subtasks in loops.
941	>	* Immediately performs the base action of this task.  This method
942	>	* is designed to support extensions, and should not in general be
943	>	* called otherwise. The return value controls whether this task
944	>	* is considered to be done normally. It may return false in
945	>	* asynchronous actions that require explicit invocations of
946	>	* {@link #complete} to become joinable. It may also throw an
947	>	* (unchecked) exception to indicate abnormal exit.
948	>	*
949	>	* @return {@code true} if completed normally
950		*/
951	<	public void reinitialize() {
686	<	if ((status & COMPLETION_MASK) == EXCEPTIONAL)
687	<	exceptionMap.remove(this);
688	<	status = 0;
689	<	}
951	>	protected abstract boolean exec();
952
953		/**
954	<	* Tries to unschedule this task for execution. This method will
955	<	* typically succeed if this task is the next task that would be
956	<	* executed by the current thread, and will typically fail (return
957	<	* false) otherwise. This method may be useful when arranging
958	<	* faster local processing of tasks that could have been, but were
959	<	* not, stolen.
960	<	* @return true if unforked
954	>	* Returns, but does not unschedule or execute, a task queued by
955	>	* the current thread but not yet executed, if one is immediately
956	>	* available. There is no guarantee that this task will actually
957	>	* be polled or executed next. Conversely, this method may return
958	>	* null even if a task exists but cannot be accessed without
959	>	* contention with other threads.  This method is designed
960	>	* primarily to support extensions, and is unlikely to be useful
961	>	* otherwise.
962	>	*
963	>	* <p>This method may be invoked only from within {@code
964	>	* ForkJoinPool} 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 next task, or {@code null} if none are available
970		*/
971	<	public boolean tryUnfork() {
972	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
971	>	protected static ForkJoinTask<?> peekNextLocalTask() {
972	>	return ((ForkJoinWorkerThread) Thread.currentThread())
973	>	.peekTask();
974		}
975
976		/**
977	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
978	<	* of them or an exception is encountered. This method may be
979	<	* invoked only from within other ForkJoinTask
980	<	* computations. Attempts to invoke in other contexts result in
981	<	* exceptions or errors including ClassCastException.
982	<	* @param t1 one task
983	<	* @param t2 the other task
984	<	* @throws NullPointerException if t1 or t2 are null
985	<	* @throws RuntimeException or Error if either task did so.
977	>	* Unschedules and returns, without executing, the next task
978	>	* queued by the current thread but not yet executed.  This method
979	>	* is designed primarily to support extensions, and is unlikely to
980	>	* be useful otherwise.
981	>	*
982	>	* <p>This method may be invoked only from within {@code
983	>	* ForkJoinPool} computations (as may be determined using method
984	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
985	>	* result in exceptions or errors, possibly including {@code
986	>	* ClassCastException}.
987	>	*
988	>	* @return the next task, or {@code null} if none are available
989		*/
990	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
991	<	t2.fork();
992	<	t1.invoke();
718	<	t2.join();
990	>	protected static ForkJoinTask<?> pollNextLocalTask() {
991	>	return ((ForkJoinWorkerThread) Thread.currentThread())
992	>	.pollLocalTask();
993		}
994
995		/**
996	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
997	<	* all of them. If any task encounters an exception, others may be
998	<	* cancelled.  This method may be invoked only from within other
999	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1000	<	* result in exceptions or errors including ClassCastException.
1001	<	* @param tasks the array of tasks
1002	<	* @throws NullPointerException if tasks or any element are null.
1003	<	* @throws RuntimeException or Error if any task did so.
996	>	* Unschedules and returns, without executing, the next task
997	>	* queued by the current thread but not yet executed, if one is
998	>	* available, or if not available, a task that was forked by some
999	>	* other thread, if available. Availability may be transient, so a
1000	>	* {@code null} result does not necessarily imply quiescence
1001	>	* of the pool this task is operating in.  This method is designed
1002	>	* primarily to support extensions, and is unlikely to be useful
1003	>	* otherwise.
1004	>	*
1005	>	* <p>This method may be invoked only from within {@code
1006	>	* ForkJoinPool} computations (as may be determined using method
1007	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1008	>	* result in exceptions or errors, possibly including {@code
1009	>	* ClassCastException}.
1010	>	*
1011	>	* @return a task, or {@code null} if none are available
1012		*/
1013	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
1014	<	Throwable ex = null;
1015	<	int last = tasks.length - 1;
734	<	for (int i = last; i >= 0; --i) {
735	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
1013	>	protected static ForkJoinTask<?> pollTask() {
1014	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1015	>	.pollTask();
1016		}
1017
1018		/**
1019	<	* Forks all tasks in the collection, returning when
1020	<	* <tt>isDone</tt> holds for all of them. If any task encounters
1021	<	* an exception, others may be cancelled.  This method may be
768	<	* invoked only from within other ForkJoinTask
769	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
1019	>	* Adaptor for Runnables. This implements RunnableFuture
1020	>	* to be compliant with AbstractExecutorService constraints
1021	>	* when used in ForkJoinPool.
1022		*/
1023	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
1024	<	if (!(tasks instanceof List)) {
1025	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
1026	<	return;
1023	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1024	>	implements RunnableFuture<T> {
1025	>	final Runnable runnable;
1026	>	final T resultOnCompletion;
1027	>	T result;
1028	>	AdaptedRunnable(Runnable runnable, T result) {
1029	>	if (runnable == null) throw new NullPointerException();
1030	>	this.runnable = runnable;
1031	>	this.resultOnCompletion = result;
1032		}
1033	<	List<? extends ForkJoinTask<?>> ts =
1034	<	(List<? extends ForkJoinTask<?>>)tasks;
1035	<	Throwable ex = null;
1036	<	int last = ts.size() - 1;
1037	<	for (int i = last; i >= 0; --i) {
1038	<	ForkJoinTask<?> t = ts.get(i);
786	<	if (t == null) {
787	<	if (ex == null)
788	<	ex = new NullPointerException();
789	<	}
790	<	else if (i != 0)
791	<	t.fork();
792	<	else {
793	<	t.quietlyInvoke();
794	<	if (ex == null)
795	<	ex = t.getException();
796	<	}
797	<	}
798	<	for (int i = 1; i <= last; ++i) {
799	<	ForkJoinTask<?> t = ts.get(i);
800	<	if (t != null) {
801	<	if (ex != null)
802	<	t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
1033	>	public T getRawResult() { return result; }
1034	>	public void setRawResult(T v) { result = v; }
1035	>	public boolean exec() {
1036	>	runnable.run();
1037	>	result = resultOnCompletion;
1038	>	return true;
1039		}
1040	<	if (ex != null)
1041	<	rethrowException(ex);
1040	>	public void run() { invoke(); }
1041	>	private static final long serialVersionUID = 5232453952276885070L;
1042		}
1043
1044		/**
1045	<	* Possibly executes tasks until the pool hosting the current task
816	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
817	<	* designs in which many tasks are forked, but none are explicitly
818	<	* joined, instead executing them until all are processed.
1045	>	* Adaptor for Callables
1046		*/
1047	<	public static void helpQuiesce() {
1048	<	((ForkJoinWorkerThread)(Thread.currentThread())).
1049	<	helpQuiescePool();
1047	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1048	>	implements RunnableFuture<T> {
1049	>	final Callable<? extends T> callable;
1050	>	T result;
1051	>	AdaptedCallable(Callable<? extends T> callable) {
1052	>	if (callable == null) throw new NullPointerException();
1053	>	this.callable = callable;
1054	>	}
1055	>	public T getRawResult() { return result; }
1056	>	public void setRawResult(T v) { result = v; }
1057	>	public boolean exec() {
1058	>	try {
1059	>	result = callable.call();
1060	>	return true;
1061	>	} catch (Error err) {
1062	>	throw err;
1063	>	} catch (RuntimeException rex) {
1064	>	throw rex;
1065	>	} catch (Exception ex) {
1066	>	throw new RuntimeException(ex);
1067	>	}
1068	>	}
1069	>	public void run() { invoke(); }
1070	>	private static final long serialVersionUID = 2838392045355241008L;
1071		}
1072
1073		/**
1074	<	* Returns a estimate of how many more locally queued tasks are
1075	<	* held by the current worker thread than there are other worker
1076	<	* threads that might want to steal them.  This value may be
1077	<	* useful for heuristic decisions about whether to fork other
1078	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
1079	<	* worker should aim to maintain a small constant surplus (for
832	<	* example, 3) of tasks, and to process computations locally if
833	<	* this threshold is exceeded.
834	<	* @return the surplus number of tasks, which may be negative
1074	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1075	>	* method of the given {@code Runnable} as its action, and returns
1076	>	* a null result upon {@link #join}.
1077	>	*
1078	>	* @param runnable the runnable action
1079	>	* @return the task
1080		*/
1081	<	public static int surplus() {
1082	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
838	<	.getEstimatedSurplusTaskCount();
1081	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1082	>	return new AdaptedRunnable<Void>(runnable, null);
1083		}
1084
841	–	// Extension kit
842	–
1085		/**
1086	<	* Returns the result that would be returned by <tt>join</tt>, or
1087	<	* null if this task is not known to have been completed.  This
1088	<	* method is designed to aid debugging, as well as to support
847	<	* extensions. Its use in any other context is discouraged.
1086	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1087	>	* method of the given {@code Runnable} as its action, and returns
1088	>	* the given result upon {@link #join}.
1089		*
1090	<	* @return the result, or null if not completed.
1090	>	* @param runnable the runnable action
1091	>	* @param result the result upon completion
1092	>	* @return the task
1093		*/
1094	<	public abstract V getRawResult();
1094	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1095	>	return new AdaptedRunnable<T>(runnable, result);
1096	>	}
1097
1098		/**
1099	<	* Forces the given value to be returned as a result.  This method
1100	<	* is designed to support extensions, and should not in general be
1101	<	* called otherwise.
1099	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1100	>	* method of the given {@code Callable} as its action, and returns
1101	>	* its result upon {@link #join}, translating any checked exceptions
1102	>	* encountered into {@code RuntimeException}.
1103		*
1104	<	* @param value the value
1105	<	*/
860	<	protected abstract void setRawResult(V value);
861	<
862	<	/**
863	<	* Immediately performs the base action of this task.  This method
864	<	* is designed to support extensions, and should not in general be
865	<	* called otherwise. The return value controls whether this task
866	<	* is considered to be done normally. It may return false in
867	<	* asynchronous actions that require explicit invocations of
868	<	* <tt>complete</tt> to become joinable. It may throw exceptions
869	<	* to indicate abnormal exit.
870	<	* @return true if completed normally
871	<	* @throws Error or RuntimeException if encountered during computation
1104	>	* @param callable the callable action
1105	>	* @return the task
1106		*/
1107	<	protected abstract boolean exec();
1107	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1108	>	return new AdaptedCallable<T>(callable);
1109	>	}
1110
1111		// Serialization support
1112
1113		private static final long serialVersionUID = -7721805057305804111L;
1114
1115		/**
1116	<	* Save the state to a stream.
1116	>	* Saves the state to a stream (that is, serializes it).
1117		*
1118		* @serialData the current run status and the exception thrown
1119	<	* during execution, or null if none.
1119	>	* during execution, or {@code null} if none
1120		* @param s the stream
1121		*/
1122		private void writeObject(java.io.ObjectOutputStream s)
#	Line 890 | Line 1126 | public abstract class ForkJoinTask<V> im
1126		}
1127
1128		/**
1129	<	* Reconstitute the instance from a stream.
1129	>	* Reconstitutes the instance from a stream (that is, deserializes it).
1130	>	*
1131		* @param s the stream
1132		*/
1133		private void readObject(java.io.ObjectInputStream s)
1134		throws java.io.IOException, ClassNotFoundException {
1135		s.defaultReadObject();
899	–	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1136		Object ex = s.readObject();
1137		if (ex != null)
1138	<	setDoneExceptionally((Throwable)ex);
1138	>	setExceptionalCompletion((Throwable) ex);
1139		}
1140
1141	<	// Temporary Unsafe mechanics for preliminary release
1141	>	// Unsafe mechanics
1142
1143	<	static final Unsafe _unsafe;
1144	<	static final long statusOffset;
1143	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1144	>	private static final long statusOffset =
1145	>	objectFieldOffset("status", ForkJoinTask.class);
1146
1147	<	static {
1147	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1148		try {
1149	<	if (ForkJoinTask.class.getClassLoader() != null) {
1150	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1151	<	f.setAccessible(true);
1152	<	_unsafe = (Unsafe)f.get(null);
1153	<	}
1154	<	else
1155	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1149	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1150	>	} catch (NoSuchFieldException e) {
1151	>	// Convert Exception to corresponding Error
1152	>	NoSuchFieldError error = new NoSuchFieldError(field);
1153	>	error.initCause(e);
1154	>	throw error;
1155	>	}
1156		}
1157
1158	+	/**
1159	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1160	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1161	+	* into a jdk.
1162	+	*
1163	+	* @return a sun.misc.Unsafe
1164	+	*/
1165	+	private static sun.misc.Unsafe getUnsafe() {
1166	+	try {
1167	+	return sun.misc.Unsafe.getUnsafe();
1168	+	} catch (SecurityException se) {
1169	+	try {
1170	+	return java.security.AccessController.doPrivileged
1171	+	(new java.security
1172	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1173	+	public sun.misc.Unsafe run() throws Exception {
1174	+	java.lang.reflect.Field f = sun.misc
1175	+	.Unsafe.class.getDeclaredField("theUnsafe");
1176	+	f.setAccessible(true);
1177	+	return (sun.misc.Unsafe) f.get(null);
1178	+	}});
1179	+	} catch (java.security.PrivilegedActionException e) {
1180	+	throw new RuntimeException("Could not initialize intrinsics",
1181	+	e.getCause());
1182	+	}
1183	+	}
1184	+	}
1185		}

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