1 |
tim |
1.1 |
/* |
2 |
dl |
1.4 |
* 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 |
tim |
1.1 |
*/ |
6 |
|
|
|
7 |
|
|
package java.util.concurrent; |
8 |
dl |
1.4 |
import java.util.concurrent.atomic.*; |
9 |
dl |
1.2 |
import java.util.*; |
10 |
tim |
1.1 |
|
11 |
|
|
/** |
12 |
dl |
1.25 |
* An {@link Executor} that can schedule commands to run after a given |
13 |
dl |
1.7 |
* delay, or to execute periodically. This class is preferable to |
14 |
dl |
1.25 |
* {@link java.util.Timer} when multiple worker threads are needed, |
15 |
tim |
1.1 |
* or when the additional flexibility or capabilities of |
16 |
dl |
1.25 |
* {@link ThreadPoolExecutor} (which this class extends) are |
17 |
dl |
1.7 |
* 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 |
dl |
1.22 |
* without any real-time guarantees about when, after they are enabled, |
29 |
dl |
1.7 |
* they will commence. Tasks tied for the same execution time are |
30 |
dl |
1.22 |
* 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 |
dl |
1.25 |
* {@link java.util.Date}, to the required form. For example, to |
36 |
dl |
1.22 |
* schedule at a certain future <tt>date</tt>, you can use: |
37 |
dl |
1.23 |
* <tt>schedule(task, date.getTime() - System.currentTimeMillis(), |
38 |
dl |
1.22 |
* 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 |
tim |
1.1 |
* |
43 |
dl |
1.13 |
* <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 |
tim |
1.1 |
* @since 1.5 |
51 |
dl |
1.9 |
* @author Doug Lea |
52 |
tim |
1.1 |
*/ |
53 |
|
|
public class ScheduledExecutor extends ThreadPoolExecutor { |
54 |
|
|
|
55 |
dl |
1.4 |
/** |
56 |
dl |
1.18 |
* False if should cancel/suppress periodic tasks on shutdown. |
57 |
|
|
*/ |
58 |
|
|
private volatile boolean continueExistingPeriodicTasksAfterShutdown; |
59 |
|
|
|
60 |
|
|
/** |
61 |
|
|
* False if should cancel non-periodic tasks on shutdown. |
62 |
|
|
*/ |
63 |
|
|
private volatile boolean executeExistingDelayedTasksAfterShutdown = true; |
64 |
|
|
|
65 |
|
|
|
66 |
|
|
/** |
67 |
dl |
1.5 |
* Sequence number to break scheduling ties, and in turn to |
68 |
|
|
* guarantee FIFO order among tied entries. |
69 |
|
|
*/ |
70 |
|
|
private static final AtomicLong sequencer = new AtomicLong(0); |
71 |
tim |
1.21 |
|
72 |
|
|
private static class ScheduledCancellableTask |
73 |
|
|
extends CancellableTask implements ScheduledCancellable { |
74 |
|
|
|
75 |
dl |
1.9 |
/** Sequence number to break ties FIFO */ |
76 |
dl |
1.29 |
private final long sequenceNumber; |
77 |
dl |
1.9 |
/** The time the task is enabled to execute in nanoTime units */ |
78 |
dl |
1.27 |
private long time; |
79 |
dl |
1.28 |
/** The delay following next time, or <= 0 if non-periodic */ |
80 |
|
|
private final long period; |
81 |
dl |
1.9 |
/** true if at fixed rate; false if fixed delay */ |
82 |
|
|
private final boolean rateBased; |
83 |
|
|
|
84 |
dl |
1.4 |
/** |
85 |
dl |
1.5 |
* Creates a one-shot action with given nanoTime-based trigger time |
86 |
dl |
1.4 |
*/ |
87 |
tim |
1.21 |
ScheduledCancellableTask(Runnable r, long ns) { |
88 |
dl |
1.4 |
super(r); |
89 |
|
|
this.time = ns; |
90 |
|
|
this.period = 0; |
91 |
dl |
1.7 |
rateBased = false; |
92 |
dl |
1.4 |
this.sequenceNumber = sequencer.getAndIncrement(); |
93 |
|
|
} |
94 |
|
|
|
95 |
|
|
/** |
96 |
dl |
1.29 |
* Creates a one-shot action with given nanoTime-based trigger |
97 |
|
|
* time but does not establish the action. (This is needed for |
98 |
|
|
* the Future-based subclass). |
99 |
dl |
1.28 |
*/ |
100 |
|
|
ScheduledCancellableTask(long ns) { |
101 |
|
|
super(); |
102 |
|
|
this.time = ns; |
103 |
|
|
this.period = 0; |
104 |
|
|
rateBased = false; |
105 |
|
|
this.sequenceNumber = sequencer.getAndIncrement(); |
106 |
|
|
} |
107 |
|
|
|
108 |
|
|
/** |
109 |
dl |
1.5 |
* Creates a periodic action with given nano time and period |
110 |
dl |
1.4 |
*/ |
111 |
tim |
1.21 |
ScheduledCancellableTask(Runnable r, long ns, long period, boolean rateBased) { |
112 |
dl |
1.4 |
super(r); |
113 |
|
|
if (period <= 0) |
114 |
|
|
throw new IllegalArgumentException(); |
115 |
|
|
this.time = ns; |
116 |
|
|
this.period = period; |
117 |
dl |
1.7 |
this.rateBased = rateBased; |
118 |
dl |
1.4 |
this.sequenceNumber = sequencer.getAndIncrement(); |
119 |
|
|
} |
120 |
|
|
|
121 |
|
|
|
122 |
|
|
public long getDelay(TimeUnit unit) { |
123 |
dl |
1.12 |
long d = unit.convert(time - System.nanoTime(), |
124 |
dl |
1.29 |
TimeUnit.NANOSECONDS); |
125 |
dl |
1.12 |
return d; |
126 |
dl |
1.4 |
} |
127 |
|
|
|
128 |
|
|
public int compareTo(Object other) { |
129 |
dl |
1.18 |
if (other == this) // compare zero ONLY if same object |
130 |
dl |
1.15 |
return 0; |
131 |
tim |
1.21 |
ScheduledCancellableTask x = (ScheduledCancellableTask)other; |
132 |
dl |
1.4 |
long diff = time - x.time; |
133 |
|
|
if (diff < 0) |
134 |
|
|
return -1; |
135 |
|
|
else if (diff > 0) |
136 |
|
|
return 1; |
137 |
|
|
else if (sequenceNumber < x.sequenceNumber) |
138 |
|
|
return -1; |
139 |
|
|
else |
140 |
|
|
return 1; |
141 |
|
|
} |
142 |
|
|
|
143 |
|
|
/** |
144 |
|
|
* Return true if this is a periodic (not a one-shot) action. |
145 |
dl |
1.9 |
* @return true if periodic |
146 |
dl |
1.4 |
*/ |
147 |
|
|
public boolean isPeriodic() { |
148 |
|
|
return period > 0; |
149 |
|
|
} |
150 |
|
|
|
151 |
|
|
/** |
152 |
tim |
1.11 |
* Returns the period, or zero if non-periodic. |
153 |
|
|
* |
154 |
dl |
1.9 |
* @return the period |
155 |
dl |
1.4 |
*/ |
156 |
|
|
public long getPeriod(TimeUnit unit) { |
157 |
|
|
return unit.convert(period, TimeUnit.NANOSECONDS); |
158 |
|
|
} |
159 |
|
|
|
160 |
|
|
/** |
161 |
dl |
1.29 |
* Overrides CancellableTask version so as to not setDone if |
162 |
|
|
* periodic. |
163 |
dl |
1.28 |
*/ |
164 |
|
|
public void run() { |
165 |
|
|
if (setRunning()) { |
166 |
|
|
try { |
167 |
|
|
getRunnable().run(); |
168 |
|
|
} finally { |
169 |
|
|
if (!isPeriodic()) |
170 |
|
|
setDone(); |
171 |
|
|
} |
172 |
|
|
} |
173 |
|
|
} |
174 |
|
|
|
175 |
|
|
/** |
176 |
dl |
1.29 |
* Return a ScheduledCancellable task (which may be this task) |
177 |
|
|
* that will trigger in the period subsequent to current task, |
178 |
|
|
* or null if non-periodic or cancelled. |
179 |
dl |
1.4 |
*/ |
180 |
tim |
1.21 |
ScheduledCancellableTask nextTask() { |
181 |
dl |
1.28 |
if (period <= 0 || !reset()) |
182 |
dl |
1.4 |
return null; |
183 |
dl |
1.28 |
time = period + (rateBased ? time : System.nanoTime()); |
184 |
dl |
1.27 |
return this; |
185 |
dl |
1.4 |
} |
186 |
|
|
} |
187 |
tim |
1.21 |
|
188 |
|
|
private static class ScheduledFutureTask<V> |
189 |
|
|
extends ScheduledCancellableTask implements ScheduledFuture<V> { |
190 |
|
|
|
191 |
dl |
1.4 |
/** |
192 |
tim |
1.21 |
* Creates a ScheduledFuture that may trigger after the given delay. |
193 |
dl |
1.4 |
*/ |
194 |
tim |
1.21 |
ScheduledFutureTask(Callable<V> callable, long triggerTime) { |
195 |
dl |
1.28 |
// must set callable after super ctor call to use inner class |
196 |
|
|
super(triggerTime); |
197 |
dl |
1.4 |
setRunnable(new InnerCancellableFuture<V>(callable)); |
198 |
dl |
1.2 |
} |
199 |
|
|
|
200 |
dl |
1.4 |
public V get() throws InterruptedException, ExecutionException { |
201 |
|
|
return ((InnerCancellableFuture<V>)getRunnable()).get(); |
202 |
dl |
1.2 |
} |
203 |
|
|
|
204 |
dl |
1.4 |
public V get(long timeout, TimeUnit unit) |
205 |
|
|
throws InterruptedException, ExecutionException, TimeoutException { |
206 |
|
|
return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit); |
207 |
dl |
1.2 |
} |
208 |
tim |
1.1 |
|
209 |
dl |
1.4 |
protected void set(V v) { |
210 |
|
|
((InnerCancellableFuture<V>)getRunnable()).set(v); |
211 |
dl |
1.2 |
} |
212 |
tim |
1.1 |
|
213 |
dl |
1.4 |
protected void setException(Throwable t) { |
214 |
|
|
((InnerCancellableFuture<V>)getRunnable()).setException(t); |
215 |
|
|
} |
216 |
|
|
} |
217 |
|
|
|
218 |
|
|
|
219 |
|
|
/** |
220 |
|
|
* An annoying wrapper class to convince generics compiler to |
221 |
tim |
1.21 |
* use a DelayQueue<ScheduledCancellableTask> as a BlockingQueue<Runnable> |
222 |
dl |
1.4 |
*/ |
223 |
tim |
1.21 |
private static class DelayedWorkQueue |
224 |
|
|
extends AbstractCollection<Runnable> implements BlockingQueue<Runnable> { |
225 |
|
|
|
226 |
|
|
private final DelayQueue<ScheduledCancellableTask> dq = new DelayQueue<ScheduledCancellableTask>(); |
227 |
dl |
1.4 |
public Runnable poll() { return dq.poll(); } |
228 |
|
|
public Runnable peek() { return dq.peek(); } |
229 |
|
|
public Runnable take() throws InterruptedException { return dq.take(); } |
230 |
|
|
public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException { |
231 |
|
|
return dq.poll(timeout, unit); |
232 |
dl |
1.2 |
} |
233 |
dl |
1.12 |
|
234 |
tim |
1.21 |
public boolean add(Runnable x) { return dq.add((ScheduledCancellableTask)x); } |
235 |
|
|
public boolean offer(Runnable x) { return dq.offer((ScheduledCancellableTask)x); } |
236 |
dl |
1.29 |
public void put(Runnable x) { |
237 |
tim |
1.21 |
dq.put((ScheduledCancellableTask)x); |
238 |
dl |
1.2 |
} |
239 |
dl |
1.29 |
public boolean offer(Runnable x, long timeout, TimeUnit unit) { |
240 |
tim |
1.21 |
return dq.offer((ScheduledCancellableTask)x, timeout, unit); |
241 |
dl |
1.2 |
} |
242 |
dl |
1.12 |
|
243 |
|
|
public Runnable remove() { return dq.remove(); } |
244 |
|
|
public Runnable element() { return dq.element(); } |
245 |
|
|
public void clear() { dq.clear(); } |
246 |
|
|
|
247 |
dl |
1.4 |
public int remainingCapacity() { return dq.remainingCapacity(); } |
248 |
|
|
public boolean remove(Object x) { return dq.remove(x); } |
249 |
|
|
public boolean contains(Object x) { return dq.contains(x); } |
250 |
|
|
public int size() { return dq.size(); } |
251 |
tim |
1.11 |
public boolean isEmpty() { return dq.isEmpty(); } |
252 |
dl |
1.26 |
public Object[] toArray() { return dq.toArray(); } |
253 |
|
|
public <T> T[] toArray(T[] array) { return dq.toArray(array); } |
254 |
dl |
1.4 |
public Iterator<Runnable> iterator() { |
255 |
|
|
return new Iterator<Runnable>() { |
256 |
tim |
1.21 |
private Iterator<ScheduledCancellableTask> it = dq.iterator(); |
257 |
dl |
1.4 |
public boolean hasNext() { return it.hasNext(); } |
258 |
|
|
public Runnable next() { return it.next(); } |
259 |
|
|
public void remove() { it.remove(); } |
260 |
|
|
}; |
261 |
tim |
1.1 |
} |
262 |
dl |
1.4 |
} |
263 |
tim |
1.1 |
|
264 |
dl |
1.4 |
/** |
265 |
dl |
1.29 |
* Creates a new ScheduledExecutor with the given core pool size. |
266 |
dl |
1.4 |
* |
267 |
|
|
* @param corePoolSize the number of threads to keep in the pool, |
268 |
|
|
* even if they are idle. |
269 |
|
|
*/ |
270 |
|
|
public ScheduledExecutor(int corePoolSize) { |
271 |
|
|
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
272 |
|
|
new DelayedWorkQueue()); |
273 |
|
|
} |
274 |
tim |
1.1 |
|
275 |
dl |
1.4 |
/** |
276 |
|
|
* Creates a new ScheduledExecutor with the given initial parameters. |
277 |
|
|
* |
278 |
|
|
* @param corePoolSize the number of threads to keep in the pool, |
279 |
|
|
* even if they are idle. |
280 |
|
|
* @param threadFactory the factory to use when the executor |
281 |
|
|
* creates a new thread. |
282 |
dl |
1.28 |
* @throws NullPointerException if threadFactory is null |
283 |
dl |
1.4 |
*/ |
284 |
|
|
public ScheduledExecutor(int corePoolSize, |
285 |
|
|
ThreadFactory threadFactory) { |
286 |
|
|
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
287 |
|
|
new DelayedWorkQueue(), threadFactory); |
288 |
tim |
1.1 |
} |
289 |
|
|
|
290 |
dl |
1.4 |
/** |
291 |
|
|
* Creates a new ScheduledExecutor with the given initial parameters. |
292 |
|
|
* |
293 |
|
|
* @param corePoolSize the number of threads to keep in the pool, |
294 |
|
|
* even if they are idle. |
295 |
|
|
* @param handler the handler to use when execution is blocked |
296 |
|
|
* because the thread bounds and queue capacities are reached. |
297 |
dl |
1.28 |
* @throws NullPointerException if handler is null |
298 |
dl |
1.4 |
*/ |
299 |
|
|
public ScheduledExecutor(int corePoolSize, |
300 |
|
|
RejectedExecutionHandler handler) { |
301 |
|
|
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
302 |
|
|
new DelayedWorkQueue(), handler); |
303 |
|
|
} |
304 |
dl |
1.2 |
|
305 |
tim |
1.1 |
/** |
306 |
dl |
1.2 |
* Creates a new ScheduledExecutor with the given initial parameters. |
307 |
|
|
* |
308 |
|
|
* @param corePoolSize the number of threads to keep in the pool, |
309 |
|
|
* even if they are idle. |
310 |
dl |
1.4 |
* @param threadFactory the factory to use when the executor |
311 |
|
|
* creates a new thread. |
312 |
|
|
* @param handler the handler to use when execution is blocked |
313 |
|
|
* because the thread bounds and queue capacities are reached. |
314 |
dl |
1.28 |
* @throws NullPointerException if threadFactory or handler is null |
315 |
tim |
1.1 |
*/ |
316 |
dl |
1.4 |
public ScheduledExecutor(int corePoolSize, |
317 |
|
|
ThreadFactory threadFactory, |
318 |
|
|
RejectedExecutionHandler handler) { |
319 |
dl |
1.2 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
320 |
dl |
1.4 |
new DelayedWorkQueue(), threadFactory, handler); |
321 |
dl |
1.13 |
} |
322 |
|
|
|
323 |
|
|
/** |
324 |
|
|
* Specialized variant of ThreadPoolExecutor.execute for delayed tasks. |
325 |
|
|
*/ |
326 |
dl |
1.18 |
private void delayedExecute(Runnable command) { |
327 |
dl |
1.13 |
if (isShutdown()) { |
328 |
|
|
reject(command); |
329 |
|
|
return; |
330 |
|
|
} |
331 |
dl |
1.18 |
// Prestart a thread if necessary. We cannot prestart it |
332 |
|
|
// running the task because the task (probably) shouldn't be |
333 |
|
|
// run yet, so thread will just idle until delay elapses. |
334 |
dl |
1.13 |
if (getPoolSize() < getCorePoolSize()) |
335 |
dl |
1.18 |
prestartCoreThread(); |
336 |
dl |
1.13 |
|
337 |
dl |
1.20 |
super.getQueue().offer(command); |
338 |
dl |
1.4 |
} |
339 |
|
|
|
340 |
|
|
/** |
341 |
dl |
1.7 |
* Creates and executes a one-shot action that becomes enabled after |
342 |
dl |
1.4 |
* the given delay. |
343 |
dl |
1.6 |
* @param command the task to execute. |
344 |
|
|
* @param delay the time from now to delay execution. |
345 |
|
|
* @param unit the time unit of the delay parameter. |
346 |
|
|
* @return a handle that can be used to cancel the task. |
347 |
dl |
1.17 |
* @throws RejectedExecutionException if task cannot be scheduled |
348 |
|
|
* for execution because the executor has been shut down. |
349 |
dl |
1.30 |
* @throws NullPointerException if command is null |
350 |
dl |
1.4 |
*/ |
351 |
|
|
|
352 |
tim |
1.21 |
public ScheduledCancellable schedule(Runnable command, long delay, TimeUnit unit) { |
353 |
dl |
1.30 |
if (command == null) |
354 |
|
|
throw new NullPointerException(); |
355 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
356 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, triggerTime); |
357 |
dl |
1.13 |
delayedExecute(t); |
358 |
dl |
1.4 |
return t; |
359 |
|
|
} |
360 |
|
|
|
361 |
|
|
/** |
362 |
dl |
1.29 |
* Creates and executes a ScheduledFuture that becomes enabled after the |
363 |
|
|
* given delay. |
364 |
|
|
* @param callable the function to execute. |
365 |
|
|
* @param delay the time from now to delay execution. |
366 |
|
|
* @param unit the time unit of the delay parameter. |
367 |
|
|
* @return a ScheduledFuture that can be used to extract result or cancel. |
368 |
|
|
* @throws RejectedExecutionException if task cannot be scheduled |
369 |
|
|
* for execution because the executor has been shut down. |
370 |
dl |
1.30 |
* @throws NullPointerException if callable is null |
371 |
dl |
1.29 |
*/ |
372 |
|
|
public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) { |
373 |
dl |
1.30 |
if (callable == null) |
374 |
|
|
throw new NullPointerException(); |
375 |
dl |
1.29 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
376 |
|
|
ScheduledFutureTask<V> t = new ScheduledFutureTask<V>(callable, triggerTime); |
377 |
|
|
delayedExecute(t); |
378 |
|
|
return t; |
379 |
|
|
} |
380 |
|
|
|
381 |
|
|
/** |
382 |
dl |
1.7 |
* Creates and executes a periodic action that becomes enabled first |
383 |
dl |
1.4 |
* after the given initial delay, and subsequently with the given |
384 |
dl |
1.7 |
* period; that is executions will commence after |
385 |
|
|
* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then |
386 |
dl |
1.28 |
* <tt>initialDelay + 2 * period</tt>, and so on. The |
387 |
|
|
* task will only terminate via cancellation. |
388 |
dl |
1.6 |
* @param command the task to execute. |
389 |
|
|
* @param initialDelay the time to delay first execution. |
390 |
|
|
* @param period the period between successive executions. |
391 |
|
|
* @param unit the time unit of the delay and period parameters |
392 |
|
|
* @return a handle that can be used to cancel the task. |
393 |
|
|
* @throws RejectedExecutionException if task cannot be scheduled |
394 |
|
|
* for execution because the executor has been shut down. |
395 |
dl |
1.30 |
* @throws NullPointerException if command is null |
396 |
dl |
1.4 |
*/ |
397 |
tim |
1.21 |
public ScheduledCancellable scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) { |
398 |
dl |
1.30 |
if (command == null) |
399 |
|
|
throw new NullPointerException(); |
400 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
401 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
402 |
dl |
1.17 |
triggerTime, |
403 |
|
|
unit.toNanos(period), |
404 |
|
|
true); |
405 |
dl |
1.13 |
delayedExecute(t); |
406 |
dl |
1.4 |
return t; |
407 |
|
|
} |
408 |
|
|
|
409 |
dl |
1.7 |
/** |
410 |
|
|
* Creates and executes a periodic action that becomes enabled first |
411 |
|
|
* after the given initial delay, and and subsequently with the |
412 |
|
|
* given delay between the termination of one execution and the |
413 |
dl |
1.28 |
* commencement of the next. |
414 |
|
|
* The task will only terminate via cancellation. |
415 |
dl |
1.7 |
* @param command the task to execute. |
416 |
|
|
* @param initialDelay the time to delay first execution. |
417 |
|
|
* @param delay the delay between the termination of one |
418 |
|
|
* execution and the commencement of the next. |
419 |
|
|
* @param unit the time unit of the delay and delay parameters |
420 |
|
|
* @return a handle that can be used to cancel the task. |
421 |
|
|
* @throws RejectedExecutionException if task cannot be scheduled |
422 |
|
|
* for execution because the executor has been shut down. |
423 |
dl |
1.30 |
* @throws NullPointerException if command is null |
424 |
dl |
1.7 |
*/ |
425 |
tim |
1.21 |
public ScheduledCancellable scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) { |
426 |
dl |
1.30 |
if (command == null) |
427 |
|
|
throw new NullPointerException(); |
428 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
429 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
430 |
dl |
1.17 |
triggerTime, |
431 |
|
|
unit.toNanos(delay), |
432 |
|
|
false); |
433 |
dl |
1.13 |
delayedExecute(t); |
434 |
dl |
1.7 |
return t; |
435 |
|
|
} |
436 |
|
|
|
437 |
dl |
1.4 |
|
438 |
|
|
/** |
439 |
dl |
1.16 |
* Execute command with zero required delay. This has effect |
440 |
|
|
* equivalent to <tt>schedule(command, 0, anyUnit)</tt>. Note |
441 |
|
|
* that inspections of the queue and of the list returned by |
442 |
|
|
* <tt>shutdownNow</tt> will access the zero-delayed |
443 |
dl |
1.25 |
* {@link ScheduledCancellable}, not the <tt>command</tt> itself. |
444 |
tim |
1.11 |
* |
445 |
dl |
1.6 |
* @param command the task to execute |
446 |
|
|
* @throws RejectedExecutionException at discretion of |
447 |
|
|
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted |
448 |
|
|
* for execution because the executor has been shut down. |
449 |
dl |
1.30 |
* @throws NullPointerException if command is null |
450 |
dl |
1.4 |
*/ |
451 |
|
|
public void execute(Runnable command) { |
452 |
dl |
1.30 |
if (command == null) |
453 |
|
|
throw new NullPointerException(); |
454 |
dl |
1.4 |
schedule(command, 0, TimeUnit.NANOSECONDS); |
455 |
tim |
1.1 |
} |
456 |
|
|
|
457 |
dl |
1.18 |
|
458 |
|
|
/** |
459 |
|
|
* Set policy on whether to continue executing existing periodic |
460 |
|
|
* tasks even when this executor has been <tt>shutdown</tt>. In |
461 |
|
|
* this case, these tasks will only terminate upon |
462 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
463 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
464 |
|
|
* false. |
465 |
|
|
* @param value if true, continue after shutdown, else don't. |
466 |
|
|
*/ |
467 |
|
|
public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) { |
468 |
|
|
continueExistingPeriodicTasksAfterShutdown = value; |
469 |
|
|
if (!value && isShutdown()) |
470 |
|
|
cancelUnwantedTasks(); |
471 |
|
|
} |
472 |
|
|
|
473 |
|
|
/** |
474 |
|
|
* Get the policy on whether to continue executing existing |
475 |
|
|
* periodic tasks even when this executor has been |
476 |
|
|
* <tt>shutdown</tt>. In this case, these tasks will only |
477 |
|
|
* terminate upon <tt>shutdownNow</tt> or after setting the policy |
478 |
|
|
* to <tt>false</tt> when already shutdown. This value is by |
479 |
|
|
* default false. |
480 |
|
|
* @return true if will continue after shutdown. |
481 |
|
|
*/ |
482 |
|
|
public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy() { |
483 |
|
|
return continueExistingPeriodicTasksAfterShutdown; |
484 |
|
|
} |
485 |
|
|
|
486 |
|
|
/** |
487 |
|
|
* Set policy on whether to execute existing delayed |
488 |
|
|
* tasks even when this executor has been <tt>shutdown</tt>. In |
489 |
|
|
* this case, these tasks will only terminate upon |
490 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
491 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
492 |
|
|
* true. |
493 |
|
|
* @param value if true, execute after shutdown, else don't. |
494 |
|
|
*/ |
495 |
|
|
public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) { |
496 |
|
|
executeExistingDelayedTasksAfterShutdown = value; |
497 |
|
|
if (!value && isShutdown()) |
498 |
|
|
cancelUnwantedTasks(); |
499 |
|
|
} |
500 |
|
|
|
501 |
|
|
/** |
502 |
dl |
1.24 |
* Get policy on whether to execute existing delayed |
503 |
dl |
1.18 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
504 |
|
|
* this case, these tasks will only terminate upon |
505 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
506 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
507 |
|
|
* true. |
508 |
|
|
* @return true if will execute after shutdown. |
509 |
|
|
*/ |
510 |
|
|
public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy() { |
511 |
|
|
return executeExistingDelayedTasksAfterShutdown; |
512 |
|
|
} |
513 |
|
|
|
514 |
|
|
/** |
515 |
|
|
* Cancel and clear the queue of all tasks that should not be run |
516 |
|
|
* due to shutdown policy. |
517 |
|
|
*/ |
518 |
|
|
private void cancelUnwantedTasks() { |
519 |
|
|
boolean keepDelayed = getExecuteExistingDelayedTasksAfterShutdownPolicy(); |
520 |
|
|
boolean keepPeriodic = getContinueExistingPeriodicTasksAfterShutdownPolicy(); |
521 |
|
|
if (!keepDelayed && !keepPeriodic) |
522 |
dl |
1.20 |
super.getQueue().clear(); |
523 |
dl |
1.18 |
else if (keepDelayed || keepPeriodic) { |
524 |
dl |
1.20 |
Object[] entries = super.getQueue().toArray(); |
525 |
dl |
1.18 |
for (int i = 0; i < entries.length; ++i) { |
526 |
tim |
1.21 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
527 |
dl |
1.18 |
if (t.isPeriodic()? !keepPeriodic : !keepDelayed) |
528 |
|
|
t.cancel(false); |
529 |
|
|
} |
530 |
|
|
entries = null; |
531 |
|
|
purge(); |
532 |
|
|
} |
533 |
|
|
} |
534 |
|
|
|
535 |
|
|
/** |
536 |
|
|
* Initiates an orderly shutdown in which previously submitted |
537 |
|
|
* tasks are executed, but no new tasks will be accepted. If the |
538 |
|
|
* <tt>ExecuteExistingDelayedTasksAfterShutdownPolicy</tt> has |
539 |
|
|
* been set <tt>false</tt>, existing delayed tasks whose delays |
540 |
|
|
* have not yet elapsed are cancelled. And unless the |
541 |
dl |
1.29 |
* <tt>ContinueExistingPeriodicTasksAfterShutdownPolicy</tt> has |
542 |
dl |
1.18 |
* been set <tt>true</tt>, future executions of existing periodic |
543 |
|
|
* tasks will be cancelled. |
544 |
|
|
*/ |
545 |
|
|
public void shutdown() { |
546 |
|
|
cancelUnwantedTasks(); |
547 |
|
|
super.shutdown(); |
548 |
|
|
} |
549 |
dl |
1.20 |
|
550 |
|
|
/** |
551 |
|
|
* Attempts to stop all actively executing tasks, halts the |
552 |
|
|
* processing of waiting tasks, and returns a list of the tasks that were |
553 |
|
|
* awaiting execution. |
554 |
|
|
* |
555 |
|
|
* <p>There are no guarantees beyond best-effort attempts to stop |
556 |
|
|
* processing actively executing tasks. This implementations |
557 |
|
|
* cancels via {@link Thread#interrupt}, so if any tasks mask or |
558 |
|
|
* fail to respond to interrupts, they may never terminate. |
559 |
|
|
* |
560 |
|
|
* @return list of tasks that never commenced execution. Each |
561 |
dl |
1.25 |
* element of this list is a {@link ScheduledCancellable}, |
562 |
|
|
* including those tasks submitted using <tt>execute</tt> which |
563 |
|
|
* are for scheduling purposes used as the basis of a zero-delay |
564 |
|
|
* <tt>ScheduledCancellable</tt>. |
565 |
dl |
1.20 |
*/ |
566 |
|
|
public List shutdownNow() { |
567 |
|
|
return super.shutdownNow(); |
568 |
|
|
} |
569 |
dl |
1.18 |
|
570 |
dl |
1.4 |
/** |
571 |
dl |
1.15 |
* Removes this task from internal queue if it is present, thus |
572 |
|
|
* causing it not to be run if it has not already started. This |
573 |
|
|
* method may be useful as one part of a cancellation scheme. |
574 |
|
|
* |
575 |
|
|
* @param task the task to remove |
576 |
|
|
* @return true if the task was removed |
577 |
|
|
*/ |
578 |
|
|
public boolean remove(Runnable task) { |
579 |
dl |
1.22 |
if (task instanceof ScheduledCancellable) |
580 |
|
|
return super.remove(task); |
581 |
dl |
1.15 |
|
582 |
tim |
1.21 |
// The task might actually have been wrapped as a ScheduledCancellable |
583 |
dl |
1.15 |
// in execute(), in which case we need to maually traverse |
584 |
|
|
// looking for it. |
585 |
|
|
|
586 |
tim |
1.21 |
ScheduledCancellable wrap = null; |
587 |
dl |
1.20 |
Object[] entries = super.getQueue().toArray(); |
588 |
dl |
1.15 |
for (int i = 0; i < entries.length; ++i) { |
589 |
tim |
1.21 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
590 |
dl |
1.15 |
Runnable r = t.getRunnable(); |
591 |
|
|
if (task.equals(r)) { |
592 |
|
|
wrap = t; |
593 |
|
|
break; |
594 |
|
|
} |
595 |
|
|
} |
596 |
|
|
entries = null; |
597 |
dl |
1.20 |
return wrap != null && super.getQueue().remove(wrap); |
598 |
|
|
} |
599 |
|
|
|
600 |
|
|
|
601 |
|
|
/** |
602 |
dl |
1.22 |
* Returns the task queue used by this executor. Each element of |
603 |
dl |
1.25 |
* this queue is a {@link ScheduledCancellable}, including those |
604 |
dl |
1.22 |
* tasks submitted using <tt>execute</tt> which are for scheduling |
605 |
|
|
* purposes used as the basis of a zero-delay |
606 |
|
|
* <tt>ScheduledCancellable</tt>. Iteration over this queue is |
607 |
|
|
* </em>not</em> guaranteed to travserse tasks in the order in |
608 |
|
|
* which they will execute. |
609 |
dl |
1.20 |
* |
610 |
|
|
* @return the task queue |
611 |
|
|
*/ |
612 |
|
|
public BlockingQueue<Runnable> getQueue() { |
613 |
|
|
return super.getQueue(); |
614 |
dl |
1.15 |
} |
615 |
|
|
|
616 |
|
|
/** |
617 |
dl |
1.22 |
* Override of <tt>Executor</tt> hook method to support periodic |
618 |
|
|
* tasks. If the executed task was periodic, causes the task for |
619 |
|
|
* the next period to execute. |
620 |
tim |
1.21 |
* @param r the task (assumed to be a ScheduledCancellable) |
621 |
dl |
1.9 |
* @param t the exception |
622 |
dl |
1.4 |
*/ |
623 |
|
|
protected void afterExecute(Runnable r, Throwable t) { |
624 |
|
|
super.afterExecute(r, t); |
625 |
tim |
1.21 |
ScheduledCancellableTask next = ((ScheduledCancellableTask)r).nextTask(); |
626 |
dl |
1.18 |
if (next != null && |
627 |
|
|
(!isShutdown() || |
628 |
|
|
(getContinueExistingPeriodicTasksAfterShutdownPolicy() && |
629 |
|
|
!isTerminating()))) |
630 |
dl |
1.20 |
super.getQueue().offer(next); |
631 |
dl |
1.18 |
|
632 |
|
|
// This might have been the final executed delayed task. Wake |
633 |
|
|
// up threads to check. |
634 |
|
|
else if (isShutdown()) |
635 |
|
|
interruptIdleWorkers(); |
636 |
dl |
1.4 |
} |
637 |
tim |
1.1 |
} |