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1.1 |
/* |
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1.4 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain. Use, modify, and |
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* redistribute this code in any way without acknowledgement. |
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1.1 |
*/ |
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package java.util.concurrent; |
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1.4 |
import java.util.concurrent.atomic.*; |
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1.2 |
import java.util.*; |
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1.1 |
|
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/** |
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1.25 |
* An {@link Executor} that can schedule commands to run after a given |
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1.7 |
* delay, or to execute periodically. This class is preferable to |
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1.25 |
* {@link java.util.Timer} when multiple worker threads are needed, |
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1.1 |
* or when the additional flexibility or capabilities of |
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1.25 |
* {@link ThreadPoolExecutor} (which this class extends) are |
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1.7 |
* required. |
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* |
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* <p> The <tt>schedule</tt> methods create tasks with various delays |
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* and return a task object that can be used to cancel or check |
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* execution. The <tt>scheduleAtFixedRate</tt> and |
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* <tt>scheduleWithFixedDelay</tt> methods create and execute tasks |
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* that run periodically until cancelled. Commands submitted using |
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* the <tt>execute</tt> method are scheduled with a requested delay of |
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* zero. |
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* |
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* <p> Delayed tasks execute no sooner than they are enabled, but |
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1.22 |
* without any real-time guarantees about when, after they are enabled, |
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1.7 |
* they will commence. Tasks tied for the same execution time are |
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1.22 |
* enabled in first-in-first-out (FIFO) order of submission. |
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* |
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* <p>All <t>schedule</tt> methods accept <em>relative</em> delays and |
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* periods as arguments, not absolute times or dates. It is a simple |
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* matter to transform an absolute time represented as a |
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1.25 |
* {@link java.util.Date}, to the required form. For example, to |
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1.22 |
* schedule at a certain future <tt>date</tt>, you can use: |
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1.23 |
* <tt>schedule(task, date.getTime() - System.currentTimeMillis(), |
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1.22 |
* TimeUnit.MILLISECONDS)</tt>. Beware however that expiration of a |
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* relative delay need not coincide with the current <tt>Date</tt> at |
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* which the task is enabled due to network time synchronization |
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* protocols, clock drift, or other factors. |
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1.1 |
* |
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1.13 |
* <p>While this class inherits from {@link ThreadPoolExecutor}, a few |
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* of the inherited tuning methods are not especially useful for |
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* it. In particular, because a <tt>ScheduledExecutor</tt> always acts |
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* as a fixed-sized pool using <tt>corePoolSize</tt> threads and an |
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* unbounded queue, adjustments to <tt>maximumPoolSize</tt> have no |
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* useful effect. |
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* |
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1.1 |
* @since 1.5 |
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1.9 |
* @author Doug Lea |
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1.1 |
*/ |
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public class ScheduledExecutor extends ThreadPoolExecutor { |
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1.4 |
/** |
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1.18 |
* False if should cancel/suppress periodic tasks on shutdown. |
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*/ |
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private volatile boolean continueExistingPeriodicTasksAfterShutdown; |
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/** |
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* False if should cancel non-periodic tasks on shutdown. |
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*/ |
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private volatile boolean executeExistingDelayedTasksAfterShutdown = true; |
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/** |
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1.5 |
* Sequence number to break scheduling ties, and in turn to |
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* guarantee FIFO order among tied entries. |
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*/ |
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private static final AtomicLong sequencer = new AtomicLong(0); |
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1.21 |
|
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private static class ScheduledCancellableTask |
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extends CancellableTask implements ScheduledCancellable { |
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1.9 |
/** Sequence number to break ties FIFO */ |
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1.4 |
private final long sequenceNumber; |
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1.9 |
/** The time the task is enabled to execute in nanoTime units */ |
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1.4 |
private final long time; |
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1.9 |
/** The delay forllowing next time, or <= 0 if non-periodic */ |
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1.4 |
private final long period; |
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1.9 |
/** true if at fixed rate; false if fixed delay */ |
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private final boolean rateBased; |
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1.4 |
/** |
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1.5 |
* Creates a one-shot action with given nanoTime-based trigger time |
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1.4 |
*/ |
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1.21 |
ScheduledCancellableTask(Runnable r, long ns) { |
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1.4 |
super(r); |
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this.time = ns; |
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this.period = 0; |
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1.7 |
rateBased = false; |
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1.4 |
this.sequenceNumber = sequencer.getAndIncrement(); |
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} |
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/** |
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1.5 |
* Creates a periodic action with given nano time and period |
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1.4 |
*/ |
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1.21 |
ScheduledCancellableTask(Runnable r, long ns, long period, boolean rateBased) { |
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1.4 |
super(r); |
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if (period <= 0) |
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throw new IllegalArgumentException(); |
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this.time = ns; |
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this.period = period; |
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1.7 |
this.rateBased = rateBased; |
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1.4 |
this.sequenceNumber = sequencer.getAndIncrement(); |
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} |
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public long getDelay(TimeUnit unit) { |
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1.12 |
long d = unit.convert(time - System.nanoTime(), |
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1.7 |
TimeUnit.NANOSECONDS); |
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1.12 |
return d; |
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1.4 |
} |
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public int compareTo(Object other) { |
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1.18 |
if (other == this) // compare zero ONLY if same object |
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1.15 |
return 0; |
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1.21 |
ScheduledCancellableTask x = (ScheduledCancellableTask)other; |
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1.4 |
long diff = time - x.time; |
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if (diff < 0) |
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return -1; |
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else if (diff > 0) |
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return 1; |
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else if (sequenceNumber < x.sequenceNumber) |
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return -1; |
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else |
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return 1; |
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} |
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/** |
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* Return true if this is a periodic (not a one-shot) action. |
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1.9 |
* @return true if periodic |
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1.4 |
*/ |
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public boolean isPeriodic() { |
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return period > 0; |
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} |
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/** |
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1.11 |
* Returns the period, or zero if non-periodic. |
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* |
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1.9 |
* @return the period |
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1.4 |
*/ |
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public long getPeriod(TimeUnit unit) { |
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return unit.convert(period, TimeUnit.NANOSECONDS); |
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} |
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/** |
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1.21 |
* Return a new ScheduledCancellable that will trigger in the period |
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1.4 |
* subsequent to current task, or null if non-periodic |
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* or canceled. |
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*/ |
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1.21 |
ScheduledCancellableTask nextTask() { |
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1.4 |
if (period <= 0 || isCancelled()) |
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return null; |
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1.10 |
long nextTime = period + (rateBased ? time : System.nanoTime()); |
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1.21 |
return new ScheduledCancellableTask(getRunnable(), nextTime, period, rateBased); |
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1.4 |
} |
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} |
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1.21 |
|
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private static class ScheduledFutureTask<V> |
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extends ScheduledCancellableTask implements ScheduledFuture<V> { |
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1.4 |
/** |
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1.21 |
* Creates a ScheduledFuture that may trigger after the given delay. |
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1.4 |
*/ |
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1.21 |
ScheduledFutureTask(Callable<V> callable, long triggerTime) { |
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1.4 |
// must set after super ctor call to use inner class |
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1.17 |
super(null, triggerTime); |
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1.4 |
setRunnable(new InnerCancellableFuture<V>(callable)); |
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1.2 |
} |
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1.4 |
public V get() throws InterruptedException, ExecutionException { |
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return ((InnerCancellableFuture<V>)getRunnable()).get(); |
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1.2 |
} |
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1.4 |
public V get(long timeout, TimeUnit unit) |
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throws InterruptedException, ExecutionException, TimeoutException { |
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return ((InnerCancellableFuture<V>)getRunnable()).get(timeout, unit); |
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1.2 |
} |
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1.1 |
|
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1.4 |
protected void set(V v) { |
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((InnerCancellableFuture<V>)getRunnable()).set(v); |
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1.2 |
} |
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1.1 |
|
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1.4 |
protected void setException(Throwable t) { |
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((InnerCancellableFuture<V>)getRunnable()).setException(t); |
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} |
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} |
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/** |
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* An annoying wrapper class to convince generics compiler to |
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1.21 |
* use a DelayQueue<ScheduledCancellableTask> as a BlockingQueue<Runnable> |
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1.4 |
*/ |
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1.21 |
private static class DelayedWorkQueue |
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extends AbstractCollection<Runnable> implements BlockingQueue<Runnable> { |
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private final DelayQueue<ScheduledCancellableTask> dq = new DelayQueue<ScheduledCancellableTask>(); |
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1.4 |
public Runnable poll() { return dq.poll(); } |
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public Runnable peek() { return dq.peek(); } |
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public Runnable take() throws InterruptedException { return dq.take(); } |
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public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException { |
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return dq.poll(timeout, unit); |
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1.2 |
} |
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1.12 |
|
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1.21 |
public boolean add(Runnable x) { return dq.add((ScheduledCancellableTask)x); } |
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public boolean offer(Runnable x) { return dq.offer((ScheduledCancellableTask)x); } |
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1.4 |
public void put(Runnable x) throws InterruptedException { |
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1.21 |
dq.put((ScheduledCancellableTask)x); |
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1.2 |
} |
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1.4 |
public boolean offer(Runnable x, long timeout, TimeUnit unit) throws InterruptedException { |
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1.21 |
return dq.offer((ScheduledCancellableTask)x, timeout, unit); |
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1.2 |
} |
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1.12 |
|
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public Runnable remove() { return dq.remove(); } |
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public Runnable element() { return dq.element(); } |
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public void clear() { dq.clear(); } |
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1.4 |
public int remainingCapacity() { return dq.remainingCapacity(); } |
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public boolean remove(Object x) { return dq.remove(x); } |
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public boolean contains(Object x) { return dq.contains(x); } |
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public int size() { return dq.size(); } |
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1.11 |
public boolean isEmpty() { return dq.isEmpty(); } |
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1.26 |
public Object[] toArray() { return dq.toArray(); } |
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public <T> T[] toArray(T[] array) { return dq.toArray(array); } |
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1.4 |
public Iterator<Runnable> iterator() { |
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return new Iterator<Runnable>() { |
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1.21 |
private Iterator<ScheduledCancellableTask> it = dq.iterator(); |
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1.4 |
public boolean hasNext() { return it.hasNext(); } |
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public Runnable next() { return it.next(); } |
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public void remove() { it.remove(); } |
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}; |
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1.1 |
} |
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dl |
1.4 |
} |
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tim |
1.1 |
|
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dl |
1.4 |
/** |
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* Creates a new ScheduledExecutor with the given initial parameters. |
238 |
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* |
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* @param corePoolSize the number of threads to keep in the pool, |
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* even if they are idle. |
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*/ |
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public ScheduledExecutor(int corePoolSize) { |
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super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
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new DelayedWorkQueue()); |
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} |
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tim |
1.1 |
|
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dl |
1.4 |
/** |
248 |
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* Creates a new ScheduledExecutor with the given initial parameters. |
249 |
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* |
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* @param corePoolSize the number of threads to keep in the pool, |
251 |
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* even if they are idle. |
252 |
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* @param threadFactory the factory to use when the executor |
253 |
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* creates a new thread. |
254 |
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*/ |
255 |
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public ScheduledExecutor(int corePoolSize, |
256 |
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ThreadFactory threadFactory) { |
257 |
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super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
258 |
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new DelayedWorkQueue(), threadFactory); |
259 |
tim |
1.1 |
} |
260 |
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261 |
dl |
1.4 |
/** |
262 |
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* Creates a new ScheduledExecutor with the given initial parameters. |
263 |
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* |
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* @param corePoolSize the number of threads to keep in the pool, |
265 |
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* even if they are idle. |
266 |
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* @param handler the handler to use when execution is blocked |
267 |
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* because the thread bounds and queue capacities are reached. |
268 |
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*/ |
269 |
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public ScheduledExecutor(int corePoolSize, |
270 |
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RejectedExecutionHandler handler) { |
271 |
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super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
272 |
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new DelayedWorkQueue(), handler); |
273 |
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} |
274 |
dl |
1.2 |
|
275 |
tim |
1.1 |
/** |
276 |
dl |
1.2 |
* Creates a new ScheduledExecutor with the given initial parameters. |
277 |
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* |
278 |
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* @param corePoolSize the number of threads to keep in the pool, |
279 |
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* even if they are idle. |
280 |
dl |
1.4 |
* @param threadFactory the factory to use when the executor |
281 |
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* creates a new thread. |
282 |
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* @param handler the handler to use when execution is blocked |
283 |
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* because the thread bounds and queue capacities are reached. |
284 |
tim |
1.1 |
*/ |
285 |
dl |
1.4 |
public ScheduledExecutor(int corePoolSize, |
286 |
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ThreadFactory threadFactory, |
287 |
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RejectedExecutionHandler handler) { |
288 |
dl |
1.2 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
289 |
dl |
1.4 |
new DelayedWorkQueue(), threadFactory, handler); |
290 |
dl |
1.13 |
} |
291 |
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292 |
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/** |
293 |
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* Specialized variant of ThreadPoolExecutor.execute for delayed tasks. |
294 |
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*/ |
295 |
dl |
1.18 |
private void delayedExecute(Runnable command) { |
296 |
dl |
1.13 |
if (isShutdown()) { |
297 |
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reject(command); |
298 |
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return; |
299 |
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} |
300 |
dl |
1.18 |
// Prestart a thread if necessary. We cannot prestart it |
301 |
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// running the task because the task (probably) shouldn't be |
302 |
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// run yet, so thread will just idle until delay elapses. |
303 |
dl |
1.13 |
if (getPoolSize() < getCorePoolSize()) |
304 |
dl |
1.18 |
prestartCoreThread(); |
305 |
dl |
1.13 |
|
306 |
dl |
1.20 |
super.getQueue().offer(command); |
307 |
dl |
1.4 |
} |
308 |
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|
309 |
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/** |
310 |
dl |
1.7 |
* Creates and executes a one-shot action that becomes enabled after |
311 |
dl |
1.4 |
* the given delay. |
312 |
dl |
1.6 |
* @param command the task to execute. |
313 |
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* @param delay the time from now to delay execution. |
314 |
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* @param unit the time unit of the delay parameter. |
315 |
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* @return a handle that can be used to cancel the task. |
316 |
dl |
1.17 |
* @throws RejectedExecutionException if task cannot be scheduled |
317 |
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* for execution because the executor has been shut down. |
318 |
dl |
1.4 |
*/ |
319 |
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|
320 |
tim |
1.21 |
public ScheduledCancellable schedule(Runnable command, long delay, TimeUnit unit) { |
321 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
322 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, triggerTime); |
323 |
dl |
1.13 |
delayedExecute(t); |
324 |
dl |
1.4 |
return t; |
325 |
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} |
326 |
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327 |
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/** |
328 |
dl |
1.7 |
* Creates and executes a periodic action that becomes enabled first |
329 |
dl |
1.4 |
* after the given initial delay, and subsequently with the given |
330 |
dl |
1.7 |
* period; that is executions will commence after |
331 |
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* <tt>initialDelay</tt> then <tt>initialDelay+period</tt>, then |
332 |
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* <tt>initialDelay + 2 * period</tt>, and so on. |
333 |
dl |
1.6 |
* @param command the task to execute. |
334 |
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* @param initialDelay the time to delay first execution. |
335 |
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* @param period the period between successive executions. |
336 |
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* @param unit the time unit of the delay and period parameters |
337 |
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* @return a handle that can be used to cancel the task. |
338 |
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* @throws RejectedExecutionException if task cannot be scheduled |
339 |
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* for execution because the executor has been shut down. |
340 |
dl |
1.4 |
*/ |
341 |
tim |
1.21 |
public ScheduledCancellable scheduleAtFixedRate(Runnable command, long initialDelay, long period, TimeUnit unit) { |
342 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
343 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
344 |
dl |
1.17 |
triggerTime, |
345 |
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unit.toNanos(period), |
346 |
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true); |
347 |
dl |
1.13 |
delayedExecute(t); |
348 |
dl |
1.4 |
return t; |
349 |
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} |
350 |
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|
351 |
dl |
1.7 |
|
352 |
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/** |
353 |
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* Creates and executes a periodic action that becomes enabled first |
354 |
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* after the given initial delay, and and subsequently with the |
355 |
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* given delay between the termination of one execution and the |
356 |
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|
* commencement of the next. |
357 |
|
|
* @param command the task to execute. |
358 |
|
|
* @param initialDelay the time to delay first execution. |
359 |
|
|
* @param delay the delay between the termination of one |
360 |
|
|
* execution and the commencement of the next. |
361 |
|
|
* @param unit the time unit of the delay and delay parameters |
362 |
|
|
* @return a handle that can be used to cancel the task. |
363 |
|
|
* @throws RejectedExecutionException if task cannot be scheduled |
364 |
|
|
* for execution because the executor has been shut down. |
365 |
|
|
*/ |
366 |
tim |
1.21 |
public ScheduledCancellable scheduleWithFixedDelay(Runnable command, long initialDelay, long delay, TimeUnit unit) { |
367 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(initialDelay); |
368 |
tim |
1.21 |
ScheduledCancellableTask t = new ScheduledCancellableTask(command, |
369 |
dl |
1.17 |
triggerTime, |
370 |
|
|
unit.toNanos(delay), |
371 |
|
|
false); |
372 |
dl |
1.13 |
delayedExecute(t); |
373 |
dl |
1.7 |
return t; |
374 |
|
|
} |
375 |
|
|
|
376 |
|
|
/** |
377 |
tim |
1.21 |
* Creates and executes a ScheduledFuture that becomes enabled after the |
378 |
dl |
1.7 |
* given delay. |
379 |
dl |
1.6 |
* @param callable the function to execute. |
380 |
|
|
* @param delay the time from now to delay execution. |
381 |
|
|
* @param unit the time unit of the delay parameter. |
382 |
tim |
1.21 |
* @return a ScheduledFuture that can be used to extract result or cancel. |
383 |
dl |
1.6 |
* @throws RejectedExecutionException if task cannot be scheduled |
384 |
|
|
* for execution because the executor has been shut down. |
385 |
dl |
1.4 |
*/ |
386 |
tim |
1.21 |
public <V> ScheduledFuture<V> schedule(Callable<V> callable, long delay, TimeUnit unit) { |
387 |
dl |
1.17 |
long triggerTime = System.nanoTime() + unit.toNanos(delay); |
388 |
tim |
1.21 |
ScheduledFutureTask<V> t = new ScheduledFutureTask<V>(callable, triggerTime); |
389 |
dl |
1.13 |
delayedExecute(t); |
390 |
dl |
1.4 |
return t; |
391 |
|
|
} |
392 |
|
|
|
393 |
|
|
/** |
394 |
dl |
1.16 |
* Execute command with zero required delay. This has effect |
395 |
|
|
* equivalent to <tt>schedule(command, 0, anyUnit)</tt>. Note |
396 |
|
|
* that inspections of the queue and of the list returned by |
397 |
|
|
* <tt>shutdownNow</tt> will access the zero-delayed |
398 |
dl |
1.25 |
* {@link ScheduledCancellable}, not the <tt>command</tt> itself. |
399 |
tim |
1.11 |
* |
400 |
dl |
1.6 |
* @param command the task to execute |
401 |
|
|
* @throws RejectedExecutionException at discretion of |
402 |
|
|
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted |
403 |
|
|
* for execution because the executor has been shut down. |
404 |
dl |
1.4 |
*/ |
405 |
|
|
public void execute(Runnable command) { |
406 |
|
|
schedule(command, 0, TimeUnit.NANOSECONDS); |
407 |
tim |
1.1 |
} |
408 |
|
|
|
409 |
dl |
1.18 |
|
410 |
|
|
/** |
411 |
|
|
* Set policy on whether to continue executing existing periodic |
412 |
|
|
* tasks even when this executor has been <tt>shutdown</tt>. In |
413 |
|
|
* this case, these tasks will only terminate upon |
414 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
415 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
416 |
|
|
* false. |
417 |
|
|
* @param value if true, continue after shutdown, else don't. |
418 |
|
|
*/ |
419 |
|
|
public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) { |
420 |
|
|
continueExistingPeriodicTasksAfterShutdown = value; |
421 |
|
|
if (!value && isShutdown()) |
422 |
|
|
cancelUnwantedTasks(); |
423 |
|
|
} |
424 |
|
|
|
425 |
|
|
/** |
426 |
|
|
* Get the policy on whether to continue executing existing |
427 |
|
|
* periodic tasks even when this executor has been |
428 |
|
|
* <tt>shutdown</tt>. In this case, these tasks will only |
429 |
|
|
* terminate upon <tt>shutdownNow</tt> or after setting the policy |
430 |
|
|
* to <tt>false</tt> when already shutdown. This value is by |
431 |
|
|
* default false. |
432 |
|
|
* @return true if will continue after shutdown. |
433 |
|
|
*/ |
434 |
|
|
public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy() { |
435 |
|
|
return continueExistingPeriodicTasksAfterShutdown; |
436 |
|
|
} |
437 |
|
|
|
438 |
|
|
/** |
439 |
|
|
* Set policy on whether to execute existing delayed |
440 |
|
|
* tasks even when this executor has been <tt>shutdown</tt>. In |
441 |
|
|
* this case, these tasks will only terminate upon |
442 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
443 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
444 |
|
|
* true. |
445 |
|
|
* @param value if true, execute after shutdown, else don't. |
446 |
|
|
*/ |
447 |
|
|
public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) { |
448 |
|
|
executeExistingDelayedTasksAfterShutdown = value; |
449 |
|
|
if (!value && isShutdown()) |
450 |
|
|
cancelUnwantedTasks(); |
451 |
|
|
} |
452 |
|
|
|
453 |
|
|
/** |
454 |
dl |
1.24 |
* Get policy on whether to execute existing delayed |
455 |
dl |
1.18 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
456 |
|
|
* this case, these tasks will only terminate upon |
457 |
|
|
* <tt>shutdownNow</tt>, or after setting the policy to |
458 |
|
|
* <tt>false</tt> when already shutdown. This value is by default |
459 |
|
|
* true. |
460 |
|
|
* @return true if will execute after shutdown. |
461 |
|
|
*/ |
462 |
|
|
public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy() { |
463 |
|
|
return executeExistingDelayedTasksAfterShutdown; |
464 |
|
|
} |
465 |
|
|
|
466 |
|
|
/** |
467 |
|
|
* Cancel and clear the queue of all tasks that should not be run |
468 |
|
|
* due to shutdown policy. |
469 |
|
|
*/ |
470 |
|
|
private void cancelUnwantedTasks() { |
471 |
|
|
boolean keepDelayed = getExecuteExistingDelayedTasksAfterShutdownPolicy(); |
472 |
|
|
boolean keepPeriodic = getContinueExistingPeriodicTasksAfterShutdownPolicy(); |
473 |
|
|
if (!keepDelayed && !keepPeriodic) |
474 |
dl |
1.20 |
super.getQueue().clear(); |
475 |
dl |
1.18 |
else if (keepDelayed || keepPeriodic) { |
476 |
dl |
1.20 |
Object[] entries = super.getQueue().toArray(); |
477 |
dl |
1.18 |
for (int i = 0; i < entries.length; ++i) { |
478 |
tim |
1.21 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
479 |
dl |
1.18 |
if (t.isPeriodic()? !keepPeriodic : !keepDelayed) |
480 |
|
|
t.cancel(false); |
481 |
|
|
} |
482 |
|
|
entries = null; |
483 |
|
|
purge(); |
484 |
|
|
} |
485 |
|
|
} |
486 |
|
|
|
487 |
|
|
/** |
488 |
|
|
* Initiates an orderly shutdown in which previously submitted |
489 |
|
|
* tasks are executed, but no new tasks will be accepted. If the |
490 |
|
|
* <tt>ExecuteExistingDelayedTasksAfterShutdownPolicy</tt> has |
491 |
|
|
* been set <tt>false</tt>, existing delayed tasks whose delays |
492 |
|
|
* have not yet elapsed are cancelled. And unless the |
493 |
dl |
1.19 |
* <tt>ContinueExistingPeriodicTasksAfterShutdownPolicy</tt> hase |
494 |
dl |
1.18 |
* been set <tt>true</tt>, future executions of existing periodic |
495 |
|
|
* tasks will be cancelled. |
496 |
|
|
*/ |
497 |
|
|
public void shutdown() { |
498 |
|
|
cancelUnwantedTasks(); |
499 |
|
|
super.shutdown(); |
500 |
|
|
} |
501 |
dl |
1.20 |
|
502 |
|
|
/** |
503 |
|
|
* Attempts to stop all actively executing tasks, halts the |
504 |
|
|
* processing of waiting tasks, and returns a list of the tasks that were |
505 |
|
|
* awaiting execution. |
506 |
|
|
* |
507 |
|
|
* <p>There are no guarantees beyond best-effort attempts to stop |
508 |
|
|
* processing actively executing tasks. This implementations |
509 |
|
|
* cancels via {@link Thread#interrupt}, so if any tasks mask or |
510 |
|
|
* fail to respond to interrupts, they may never terminate. |
511 |
|
|
* |
512 |
|
|
* @return list of tasks that never commenced execution. Each |
513 |
dl |
1.25 |
* element of this list is a {@link ScheduledCancellable}, |
514 |
|
|
* including those tasks submitted using <tt>execute</tt> which |
515 |
|
|
* are for scheduling purposes used as the basis of a zero-delay |
516 |
|
|
* <tt>ScheduledCancellable</tt>. |
517 |
dl |
1.20 |
*/ |
518 |
|
|
public List shutdownNow() { |
519 |
|
|
return super.shutdownNow(); |
520 |
|
|
} |
521 |
dl |
1.18 |
|
522 |
dl |
1.4 |
/** |
523 |
dl |
1.15 |
* 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 |
dl |
1.22 |
if (task instanceof ScheduledCancellable) |
532 |
|
|
return super.remove(task); |
533 |
dl |
1.15 |
|
534 |
tim |
1.21 |
// The task might actually have been wrapped as a ScheduledCancellable |
535 |
dl |
1.15 |
// in execute(), in which case we need to maually traverse |
536 |
|
|
// looking for it. |
537 |
|
|
|
538 |
tim |
1.21 |
ScheduledCancellable wrap = null; |
539 |
dl |
1.20 |
Object[] entries = super.getQueue().toArray(); |
540 |
dl |
1.15 |
for (int i = 0; i < entries.length; ++i) { |
541 |
tim |
1.21 |
ScheduledCancellableTask t = (ScheduledCancellableTask)entries[i]; |
542 |
dl |
1.15 |
Runnable r = t.getRunnable(); |
543 |
|
|
if (task.equals(r)) { |
544 |
|
|
wrap = t; |
545 |
|
|
break; |
546 |
|
|
} |
547 |
|
|
} |
548 |
|
|
entries = null; |
549 |
dl |
1.20 |
return wrap != null && super.getQueue().remove(wrap); |
550 |
|
|
} |
551 |
|
|
|
552 |
|
|
|
553 |
|
|
/** |
554 |
dl |
1.22 |
* Returns the task queue used by this executor. Each element of |
555 |
dl |
1.25 |
* this queue is a {@link ScheduledCancellable}, including those |
556 |
dl |
1.22 |
* 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 |
dl |
1.20 |
* |
562 |
|
|
* @return the task queue |
563 |
|
|
*/ |
564 |
|
|
public BlockingQueue<Runnable> getQueue() { |
565 |
|
|
return super.getQueue(); |
566 |
dl |
1.15 |
} |
567 |
|
|
|
568 |
|
|
/** |
569 |
dl |
1.22 |
* 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 |
tim |
1.21 |
* @param r the task (assumed to be a ScheduledCancellable) |
573 |
dl |
1.9 |
* @param t the exception |
574 |
dl |
1.4 |
*/ |
575 |
|
|
protected void afterExecute(Runnable r, Throwable t) { |
576 |
|
|
super.afterExecute(r, t); |
577 |
tim |
1.21 |
ScheduledCancellableTask next = ((ScheduledCancellableTask)r).nextTask(); |
578 |
dl |
1.18 |
if (next != null && |
579 |
|
|
(!isShutdown() || |
580 |
|
|
(getContinueExistingPeriodicTasksAfterShutdownPolicy() && |
581 |
|
|
!isTerminating()))) |
582 |
dl |
1.20 |
super.getQueue().offer(next); |
583 |
dl |
1.18 |
|
584 |
|
|
// This might have been the final executed delayed task. Wake |
585 |
|
|
// up threads to check. |
586 |
|
|
else if (isShutdown()) |
587 |
|
|
interruptIdleWorkers(); |
588 |
dl |
1.4 |
} |
589 |
tim |
1.1 |
} |