1 |
/* |
2 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
* Expert Group and released to the public domain. Use, modify, and |
4 |
* redistribute this code in any way without acknowledgement. |
5 |
*/ |
6 |
|
7 |
package java.util.concurrent; |
8 |
import java.util.concurrent.atomic.*; |
9 |
import java.util.*; |
10 |
|
11 |
/** |
12 |
* An <tt>Executor</tt> that can schedule commands to run after a given |
13 |
* delay, or to execute periodically. This class is preferable to |
14 |
* <tt>java.util.Timer</tt> when multiple worker threads are needed, |
15 |
* or when the additional flexibility or capabilities of |
16 |
* <tt>ThreadPoolExecutor</tt> (which this class extends) are |
17 |
* required. |
18 |
* |
19 |
* <p> The <tt>schedule</tt> methods create tasks with various delays |
20 |
* and return a task object that can be used to cancel or check |
21 |
* execution. The <tt>scheduleAtFixedRate</tt> and |
22 |
* <tt>scheduleWithFixedDelay</tt> methods create and execute tasks |
23 |
* that run periodically until cancelled. Commands submitted using |
24 |
* the <tt>execute</tt> method are scheduled with a requested delay of |
25 |
* zero. |
26 |
* |
27 |
* <p> Delayed tasks execute no sooner than they are enabled, but |
28 |
* without any real-time guarantees about when, after they are enabled, |
29 |
* they will commence. Tasks tied for the same execution time are |
30 |
* enabled in first-in-first-out (FIFO) order of submission. |
31 |
* |
32 |
* <p>All <t>schedule</tt> methods accept <em>relative</em> delays and |
33 |
* periods as arguments, not absolute times or dates. It is a simple |
34 |
* matter to transform an absolute time represented as a |
35 |
* <tt>java.util.Date</tt>, to the required form. For example, to |
36 |
* schedule at a certain future <tt>date</tt>, you can use: |
37 |
* <tt>schedule(task, date.getTime() - System.currentTimeMillis(), |
38 |
* TimeUnit.MILLISECONDS)</tt>. Beware however that expiration of a |
39 |
* relative delay need not coincide with the current <tt>Date</tt> at |
40 |
* which the task is enabled due to network time synchronization |
41 |
* protocols, clock drift, or other factors. |
42 |
* |
43 |
* <p>While this class inherits from {@link ThreadPoolExecutor}, a few |
44 |
* of the inherited tuning methods are not especially useful for |
45 |
* it. In particular, because a <tt>ScheduledExecutor</tt> always acts |
46 |
* as a fixed-sized pool using <tt>corePoolSize</tt> threads and an |
47 |
* unbounded queue, adjustments to <tt>maximumPoolSize</tt> have no |
48 |
* useful effect. |
49 |
* |
50 |
* @since 1.5 |
51 |
* @see Executors |
52 |
* |
53 |
* @spec JSR-166 |
54 |
* @author Doug Lea |
55 |
*/ |
56 |
public class ScheduledExecutor extends ThreadPoolExecutor { |
57 |
|
58 |
/** |
59 |
* False if should cancel/suppress periodic tasks on shutdown. |
60 |
*/ |
61 |
private volatile boolean continueExistingPeriodicTasksAfterShutdown; |
62 |
|
63 |
/** |
64 |
* False if should cancel non-periodic tasks on shutdown. |
65 |
*/ |
66 |
private volatile boolean executeExistingDelayedTasksAfterShutdown = true; |
67 |
|
68 |
|
69 |
/** |
70 |
* Sequence number to break scheduling ties, and in turn to |
71 |
* guarantee FIFO order among tied entries. |
72 |
*/ |
73 |
private static final AtomicLong sequencer = new AtomicLong(0); |
74 |
|
75 |
private static class ScheduledCancellableTask |
76 |
extends CancellableTask implements ScheduledCancellable { |
77 |
|
78 |
/** Sequence number to break ties FIFO */ |
79 |
private final long sequenceNumber; |
80 |
/** The time the task is enabled to execute in nanoTime units */ |
81 |
private final long time; |
82 |
/** The delay forllowing next time, or <= 0 if non-periodic */ |
83 |
private final long period; |
84 |
/** true if at fixed rate; false if fixed delay */ |
85 |
private final boolean rateBased; |
86 |
|
87 |
/** |
88 |
* Creates a one-shot action with given nanoTime-based trigger time |
89 |
*/ |
90 |
ScheduledCancellableTask(Runnable r, long ns) { |
91 |
super(r); |
92 |
this.time = ns; |
93 |
this.period = 0; |
94 |
rateBased = false; |
95 |
this.sequenceNumber = sequencer.getAndIncrement(); |
96 |
} |
97 |
|
98 |
/** |
99 |
* Creates a periodic action with given nano time and period |
100 |
*/ |
101 |
ScheduledCancellableTask(Runnable r, long ns, long period, boolean rateBased) { |
102 |
super(r); |
103 |
if (period <= 0) |
104 |
throw new IllegalArgumentException(); |
105 |
this.time = ns; |
106 |
this.period = period; |
107 |
this.rateBased = rateBased; |
108 |
this.sequenceNumber = sequencer.getAndIncrement(); |
109 |
} |
110 |
|
111 |
|
112 |
public long getDelay(TimeUnit unit) { |
113 |
long d = unit.convert(time - System.nanoTime(), |
114 |
TimeUnit.NANOSECONDS); |
115 |
return d; |
116 |
} |
117 |
|
118 |
public int compareTo(Object other) { |
119 |
if (other == this) // compare zero ONLY if same object |
120 |
return 0; |
121 |
ScheduledCancellableTask x = (ScheduledCancellableTask)other; |
122 |
long diff = time - x.time; |
123 |
if (diff < 0) |
124 |
return -1; |
125 |
else if (diff > 0) |
126 |
return 1; |
127 |
else if (sequenceNumber < x.sequenceNumber) |
128 |
return -1; |
129 |
else |
130 |
return 1; |
131 |
} |
132 |
|
133 |
/** |
134 |
* Return true if this is a periodic (not a one-shot) action. |
135 |
* @return true if periodic |
136 |
*/ |
137 |
public boolean isPeriodic() { |
138 |
return period > 0; |
139 |
} |
140 |
|
141 |
/** |
142 |
* Returns the period, or zero if non-periodic. |
143 |
* |
144 |
* @return the period |
145 |
*/ |
146 |
public long getPeriod(TimeUnit unit) { |
147 |
return unit.convert(period, TimeUnit.NANOSECONDS); |
148 |
} |
149 |
|
150 |
/** |
151 |
* Return a new ScheduledCancellable that will trigger in the period |
152 |
* subsequent to current task, or null if non-periodic |
153 |
* or canceled. |
154 |
*/ |
155 |
ScheduledCancellableTask nextTask() { |
156 |
if (period <= 0 || isCancelled()) |
157 |
return null; |
158 |
long nextTime = period + (rateBased ? time : System.nanoTime()); |
159 |
return new ScheduledCancellableTask(getRunnable(), nextTime, period, rateBased); |
160 |
} |
161 |
} |
162 |
|
163 |
private static class ScheduledFutureTask<V> |
164 |
extends ScheduledCancellableTask implements ScheduledFuture<V> { |
165 |
|
166 |
/** |
167 |
* Creates a ScheduledFuture that may trigger after the given delay. |
168 |
*/ |
169 |
ScheduledFutureTask(Callable<V> callable, long triggerTime) { |
170 |
// must set after super ctor call to use inner class |
171 |
super(null, triggerTime); |
172 |
setRunnable(new InnerCancellableFuture<V>(callable)); |
173 |
} |
174 |
|
175 |
public V get() throws InterruptedException, ExecutionException { |
176 |
return ((InnerCancellableFuture<V>)getRunnable()).get(); |
177 |
} |
178 |
|
179 |
public V get(long timeout, TimeUnit unit) |
180 |
throws InterruptedException, ExecutionException, TimeoutException { |
181 |
return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit); |
182 |
} |
183 |
|
184 |
protected void set(V v) { |
185 |
((InnerCancellableFuture<V>)getRunnable()).set(v); |
186 |
} |
187 |
|
188 |
protected void setException(Throwable t) { |
189 |
((InnerCancellableFuture<V>)getRunnable()).setException(t); |
190 |
} |
191 |
} |
192 |
|
193 |
|
194 |
/** |
195 |
* An annoying wrapper class to convince generics compiler to |
196 |
* use a DelayQueue<ScheduledCancellableTask> as a BlockingQueue<Runnable> |
197 |
*/ |
198 |
private static class DelayedWorkQueue |
199 |
extends AbstractCollection<Runnable> implements BlockingQueue<Runnable> { |
200 |
|
201 |
private final DelayQueue<ScheduledCancellableTask> dq = new DelayQueue<ScheduledCancellableTask>(); |
202 |
public Runnable poll() { return dq.poll(); } |
203 |
public Runnable peek() { return dq.peek(); } |
204 |
public Runnable take() throws InterruptedException { return dq.take(); } |
205 |
public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException { |
206 |
return dq.poll(timeout, unit); |
207 |
} |
208 |
|
209 |
public boolean add(Runnable x) { return dq.add((ScheduledCancellableTask)x); } |
210 |
public boolean offer(Runnable x) { return dq.offer((ScheduledCancellableTask)x); } |
211 |
public void put(Runnable x) throws InterruptedException { |
212 |
dq.put((ScheduledCancellableTask)x); |
213 |
} |
214 |
public boolean offer(Runnable x, long timeout, TimeUnit unit) throws InterruptedException { |
215 |
return dq.offer((ScheduledCancellableTask)x, timeout, unit); |
216 |
} |
217 |
|
218 |
public Runnable remove() { return dq.remove(); } |
219 |
public Runnable element() { return dq.element(); } |
220 |
public void clear() { dq.clear(); } |
221 |
|
222 |
public int remainingCapacity() { return dq.remainingCapacity(); } |
223 |
public boolean remove(Object x) { return dq.remove(x); } |
224 |
public boolean contains(Object x) { return dq.contains(x); } |
225 |
public int size() { return dq.size(); } |
226 |
public boolean isEmpty() { return dq.isEmpty(); } |
227 |
public Iterator<Runnable> iterator() { |
228 |
return new Iterator<Runnable>() { |
229 |
private Iterator<ScheduledCancellableTask> it = dq.iterator(); |
230 |
public boolean hasNext() { return it.hasNext(); } |
231 |
public Runnable next() { return it.next(); } |
232 |
public void remove() { it.remove(); } |
233 |
}; |
234 |
} |
235 |
} |
236 |
|
237 |
/** |
238 |
* Creates a new ScheduledExecutor with the given initial parameters. |
239 |
* |
240 |
* @param corePoolSize the number of threads to keep in the pool, |
241 |
* even if they are idle. |
242 |
*/ |
243 |
public ScheduledExecutor(int corePoolSize) { |
244 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
245 |
new DelayedWorkQueue()); |
246 |
} |
247 |
|
248 |
/** |
249 |
* Creates a new ScheduledExecutor with the given initial parameters. |
250 |
* |
251 |
* @param corePoolSize the number of threads to keep in the pool, |
252 |
* even if they are idle. |
253 |
* @param threadFactory the factory to use when the executor |
254 |
* creates a new thread. |
255 |
*/ |
256 |
public ScheduledExecutor(int corePoolSize, |
257 |
ThreadFactory threadFactory) { |
258 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
259 |
new DelayedWorkQueue(), threadFactory); |
260 |
} |
261 |
|
262 |
/** |
263 |
* Creates a new ScheduledExecutor with the given initial parameters. |
264 |
* |
265 |
* @param corePoolSize the number of threads to keep in the pool, |
266 |
* even if they are idle. |
267 |
* @param handler the handler to use when execution is blocked |
268 |
* because the thread bounds and queue capacities are reached. |
269 |
*/ |
270 |
public ScheduledExecutor(int corePoolSize, |
271 |
RejectedExecutionHandler handler) { |
272 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
273 |
new DelayedWorkQueue(), handler); |
274 |
} |
275 |
|
276 |
/** |
277 |
* Creates a new ScheduledExecutor with the given initial parameters. |
278 |
* |
279 |
* @param corePoolSize the number of threads to keep in the pool, |
280 |
* even if they are idle. |
281 |
* @param threadFactory the factory to use when the executor |
282 |
* creates a new thread. |
283 |
* @param handler the handler to use when execution is blocked |
284 |
* because the thread bounds and queue capacities are reached. |
285 |
*/ |
286 |
public ScheduledExecutor(int corePoolSize, |
287 |
ThreadFactory threadFactory, |
288 |
RejectedExecutionHandler handler) { |
289 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
290 |
new DelayedWorkQueue(), threadFactory, handler); |
291 |
} |
292 |
|
293 |
/** |
294 |
* Specialized variant of ThreadPoolExecutor.execute for delayed tasks. |
295 |
*/ |
296 |
private void delayedExecute(Runnable command) { |
297 |
if (isShutdown()) { |
298 |
reject(command); |
299 |
return; |
300 |
} |
301 |
// Prestart a thread if necessary. We cannot prestart it |
302 |
// running the task because the task (probably) shouldn't be |
303 |
// run yet, so thread will just idle until delay elapses. |
304 |
if (getPoolSize() < getCorePoolSize()) |
305 |
prestartCoreThread(); |
306 |
|
307 |
super.getQueue().offer(command); |
308 |
} |
309 |
|
310 |
/** |
311 |
* Creates and executes a one-shot action that becomes enabled after |
312 |
* the given delay. |
313 |
* @param command the task to execute. |
314 |
* @param delay the time from now to delay execution. |
315 |
* @param unit the time unit of the delay parameter. |
316 |
* @return a handle that can be used to cancel the task. |
317 |
* @throws RejectedExecutionException if task cannot be scheduled |
318 |
* for execution because the executor has been shut down. |
319 |
*/ |
320 |
|
321 |
public ScheduledCancellable schedule(Runnable command, long delay, TimeUnit unit) { |
322 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
323 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, triggerTime); |
324 |
delayedExecute(t); |
325 |
return t; |
326 |
} |
327 |
|
328 |
/** |
329 |
* Creates and executes a periodic action that becomes enabled first |
330 |
* after the given initial delay, and subsequently with the given |
331 |
* period; that is executions will commence after |
332 |
* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then |
333 |
* <tt>initialDelay + 2 * period</tt>, and so on. |
334 |
* @param command the task to execute. |
335 |
* @param initialDelay the time to delay first execution. |
336 |
* @param period the period between successive executions. |
337 |
* @param unit the time unit of the delay and period parameters |
338 |
* @return a handle that can be used to cancel the task. |
339 |
* @throws RejectedExecutionException if task cannot be scheduled |
340 |
* for execution because the executor has been shut down. |
341 |
*/ |
342 |
public ScheduledCancellable scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) { |
343 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
344 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
345 |
triggerTime, |
346 |
unit.toNanos(period), |
347 |
true); |
348 |
delayedExecute(t); |
349 |
return t; |
350 |
} |
351 |
|
352 |
|
353 |
/** |
354 |
* Creates and executes a periodic action that becomes enabled first |
355 |
* after the given initial delay, and and subsequently with the |
356 |
* given delay between the termination of one execution and the |
357 |
* commencement of the next. |
358 |
* @param command the task to execute. |
359 |
* @param initialDelay the time to delay first execution. |
360 |
* @param delay the delay between the termination of one |
361 |
* execution and the commencement of the next. |
362 |
* @param unit the time unit of the delay and delay parameters |
363 |
* @return a handle that can be used to cancel the task. |
364 |
* @throws RejectedExecutionException if task cannot be scheduled |
365 |
* for execution because the executor has been shut down. |
366 |
*/ |
367 |
public ScheduledCancellable scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) { |
368 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
369 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
370 |
triggerTime, |
371 |
unit.toNanos(delay), |
372 |
false); |
373 |
delayedExecute(t); |
374 |
return t; |
375 |
} |
376 |
|
377 |
/** |
378 |
* Creates and executes a ScheduledFuture that becomes enabled after the |
379 |
* given delay. |
380 |
* @param callable the function to execute. |
381 |
* @param delay the time from now to delay execution. |
382 |
* @param unit the time unit of the delay parameter. |
383 |
* @return a ScheduledFuture that can be used to extract result or cancel. |
384 |
* @throws RejectedExecutionException if task cannot be scheduled |
385 |
* for execution because the executor has been shut down. |
386 |
*/ |
387 |
public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) { |
388 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
389 |
ScheduledFutureTask<V> t = new ScheduledFutureTask<V>(callable, triggerTime); |
390 |
delayedExecute(t); |
391 |
return t; |
392 |
} |
393 |
|
394 |
/** |
395 |
* Execute command with zero required delay. This has effect |
396 |
* equivalent to <tt>schedule(command, 0, anyUnit)</tt>. Note |
397 |
* that inspections of the queue and of the list returned by |
398 |
* <tt>shutdownNow</tt> will access the zero-delayed |
399 |
* <tt>ScheduledCancellable</tt>, not the <tt>command</tt> itself. |
400 |
* |
401 |
* @param command the task to execute |
402 |
* @throws RejectedExecutionException at discretion of |
403 |
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted |
404 |
* for execution because the executor has been shut down. |
405 |
*/ |
406 |
public void execute(Runnable command) { |
407 |
schedule(command, 0, TimeUnit.NANOSECONDS); |
408 |
} |
409 |
|
410 |
|
411 |
/** |
412 |
* Set policy on whether to continue executing existing periodic |
413 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
414 |
* this case, these tasks will only terminate upon |
415 |
* <tt>shutdownNow</tt>, or after setting the policy to |
416 |
* <tt>false</tt> when already shutdown. This value is by default |
417 |
* false. |
418 |
* @param value if true, continue after shutdown, else don't. |
419 |
*/ |
420 |
public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) { |
421 |
continueExistingPeriodicTasksAfterShutdown = value; |
422 |
if (!value && isShutdown()) |
423 |
cancelUnwantedTasks(); |
424 |
} |
425 |
|
426 |
/** |
427 |
* Get the policy on whether to continue executing existing |
428 |
* periodic tasks even when this executor has been |
429 |
* <tt>shutdown</tt>. In this case, these tasks will only |
430 |
* terminate upon <tt>shutdownNow</tt> or after setting the policy |
431 |
* to <tt>false</tt> when already shutdown. This value is by |
432 |
* default false. |
433 |
* @return true if will continue after shutdown. |
434 |
*/ |
435 |
public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy() { |
436 |
return continueExistingPeriodicTasksAfterShutdown; |
437 |
} |
438 |
|
439 |
/** |
440 |
* Set policy on whether to execute existing delayed |
441 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
442 |
* this case, these tasks will only terminate upon |
443 |
* <tt>shutdownNow</tt>, or after setting the policy to |
444 |
* <tt>false</tt> when already shutdown. This value is by default |
445 |
* true. |
446 |
* @param value if true, execute after shutdown, else don't. |
447 |
*/ |
448 |
public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) { |
449 |
executeExistingDelayedTasksAfterShutdown = value; |
450 |
if (!value && isShutdown()) |
451 |
cancelUnwantedTasks(); |
452 |
} |
453 |
|
454 |
/** |
455 |
* Get policy on whether to execute existing delayed |
456 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
457 |
* this case, these tasks will only terminate upon |
458 |
* <tt>shutdownNow</tt>, or after setting the policy to |
459 |
* <tt>false</tt> when already shutdown. This value is by default |
460 |
* true. |
461 |
* @return true if will execute after shutdown. |
462 |
*/ |
463 |
public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy() { |
464 |
return executeExistingDelayedTasksAfterShutdown; |
465 |
} |
466 |
|
467 |
/** |
468 |
* Cancel and clear the queue of all tasks that should not be run |
469 |
* due to shutdown policy. |
470 |
*/ |
471 |
private void cancelUnwantedTasks() { |
472 |
boolean keepDelayed = getExecuteExistingDelayedTasksAfterShutdownPolicy(); |
473 |
boolean keepPeriodic = getContinueExistingPeriodicTasksAfterShutdownPolicy(); |
474 |
if (!keepDelayed && !keepPeriodic) |
475 |
super.getQueue().clear(); |
476 |
else if (keepDelayed || keepPeriodic) { |
477 |
Object[] entries = super.getQueue().toArray(); |
478 |
for (int i = 0; i < entries.length; ++i) { |
479 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
480 |
if (t.isPeriodic()? !keepPeriodic : !keepDelayed) |
481 |
t.cancel(false); |
482 |
} |
483 |
entries = null; |
484 |
purge(); |
485 |
} |
486 |
} |
487 |
|
488 |
/** |
489 |
* Initiates an orderly shutdown in which previously submitted |
490 |
* tasks are executed, but no new tasks will be accepted. If the |
491 |
* <tt>ExecuteExistingDelayedTasksAfterShutdownPolicy</tt> has |
492 |
* been set <tt>false</tt>, existing delayed tasks whose delays |
493 |
* have not yet elapsed are cancelled. And unless the |
494 |
* <tt>ContinueExistingPeriodicTasksAfterShutdownPolicy</tt> hase |
495 |
* been set <tt>true</tt>, future executions of existing periodic |
496 |
* tasks will be cancelled. |
497 |
*/ |
498 |
public void shutdown() { |
499 |
cancelUnwantedTasks(); |
500 |
super.shutdown(); |
501 |
} |
502 |
|
503 |
/** |
504 |
* Attempts to stop all actively executing tasks, halts the |
505 |
* processing of waiting tasks, and returns a list of the tasks that were |
506 |
* awaiting execution. |
507 |
* |
508 |
* <p>There are no guarantees beyond best-effort attempts to stop |
509 |
* processing actively executing tasks. This implementations |
510 |
* cancels via {@link Thread#interrupt}, so if any tasks mask or |
511 |
* fail to respond to interrupts, they may never terminate. |
512 |
* |
513 |
* @return list of tasks that never commenced execution. Each |
514 |
* element of this list is a <tt>ScheduledCancellable</tt>, including those |
515 |
* tasks submitted using <tt>execute</tt> which are for scheduling |
516 |
* purposes used as the basis of a zero-delay <tt>ScheduledCancellable</tt>. |
517 |
*/ |
518 |
public List shutdownNow() { |
519 |
return super.shutdownNow(); |
520 |
} |
521 |
|
522 |
/** |
523 |
* Removes this task from internal queue if it is present, thus |
524 |
* causing it not to be run if it has not already started. This |
525 |
* method may be useful as one part of a cancellation scheme. |
526 |
* |
527 |
* @param task the task to remove |
528 |
* @return true if the task was removed |
529 |
*/ |
530 |
public boolean remove(Runnable task) { |
531 |
if (task instanceof ScheduledCancellable) |
532 |
return super.remove(task); |
533 |
|
534 |
// The task might actually have been wrapped as a ScheduledCancellable |
535 |
// in execute(), in which case we need to maually traverse |
536 |
// looking for it. |
537 |
|
538 |
ScheduledCancellable wrap = null; |
539 |
Object[] entries = super.getQueue().toArray(); |
540 |
for (int i = 0; i < entries.length; ++i) { |
541 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
542 |
Runnable r = t.getRunnable(); |
543 |
if (task.equals(r)) { |
544 |
wrap = t; |
545 |
break; |
546 |
} |
547 |
} |
548 |
entries = null; |
549 |
return wrap != null && super.getQueue().remove(wrap); |
550 |
} |
551 |
|
552 |
|
553 |
/** |
554 |
* Returns the task queue used by this executor. Each element of |
555 |
* this queue is a <tt>ScheduledCancellable</tt>, including those |
556 |
* tasks submitted using <tt>execute</tt> which are for scheduling |
557 |
* purposes used as the basis of a zero-delay |
558 |
* <tt>ScheduledCancellable</tt>. Iteration over this queue is |
559 |
* </em>not</em> guaranteed to travserse tasks in the order in |
560 |
* which they will execute. |
561 |
* |
562 |
* @return the task queue |
563 |
*/ |
564 |
public BlockingQueue<Runnable> getQueue() { |
565 |
return super.getQueue(); |
566 |
} |
567 |
|
568 |
/** |
569 |
* Override of <tt>Executor</tt> hook method to support periodic |
570 |
* tasks. If the executed task was periodic, causes the task for |
571 |
* the next period to execute. |
572 |
* @param r the task (assumed to be a ScheduledCancellable) |
573 |
* @param t the exception |
574 |
*/ |
575 |
protected void afterExecute(Runnable r, Throwable t) { |
576 |
super.afterExecute(r, t); |
577 |
ScheduledCancellableTask next = ((ScheduledCancellableTask)r).nextTask(); |
578 |
if (next != null && |
579 |
(!isShutdown() || |
580 |
(getContinueExistingPeriodicTasksAfterShutdownPolicy() && |
581 |
!isTerminating()))) |
582 |
super.getQueue().offer(next); |
583 |
|
584 |
// This might have been the final executed delayed task. Wake |
585 |
// up threads to check. |
586 |
else if (isShutdown()) |
587 |
interruptIdleWorkers(); |
588 |
} |
589 |
} |