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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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|
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package java.util.concurrent; |
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import java.util.concurrent.atomic.*; |
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import java.util.*; |
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|
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/** |
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* A {@link ThreadPoolExecutor} that can additionally schedule |
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* commands to run after a given delay, or to execute |
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* periodically. This class is preferable to {@link java.util.Timer} |
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* when multiple worker threads are needed, or when the additional |
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* flexibility or capabilities of {@link ThreadPoolExecutor} (which |
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* this class extends) are required. |
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* |
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* <p> Delayed tasks execute no sooner than they are enabled, but |
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* without any real-time guarantees about when, after they are |
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* enabled, they will commence. Tasks scheduled for exactly the same |
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* execution time are enabled in first-in-first-out (FIFO) order of |
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* submission. |
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* |
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* <p>While this class inherits from {@link ThreadPoolExecutor}, a few |
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* of the inherited tuning methods are not useful for it. In |
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* particular, because it acts as a fixed-sized pool using |
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* <tt>corePoolSize</tt> threads and an unbounded queue, adjustments |
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* to <tt>maximumPoolSize</tt> have no useful effect. Additionally, it |
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* is almost never a good idea to set <tt>corePoolSize</tt> to zero or |
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* use <tt>allowCoreThreadTimeOut</tt> because this may leave the pool |
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* without threads to handle tasks once they become eligible to run. |
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* |
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* <p><b>Extension notes:</b> This class overrides {@link |
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* AbstractExecutorService} <tt>submit</tt> methods to generate |
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* internal objects to control per-task delays and scheduling. To |
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* preserve functionality, any further overrides of these methods in |
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* subclasses must invoke superclass versions, which effectively |
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* disables additional task customization. However, this class |
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* provides alternative protected extension method |
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* <tt>decorateTask</tt> (one version each for <tt>Runnable</tt> and |
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* <tt>Callable</tt>) that can be used to customize the concrete task |
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* types used to execute commands entered via <tt>execute</tt>, |
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* <tt>submit</tt>, <tt>schedule</tt>, <tt>scheduleAtFixedRate</tt>, |
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* and <tt>scheduleWithFixedDelay</tt>. By default, a |
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* <tt>ScheduledThreadPoolExecutor</tt> uses a task type extending |
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* {@link FutureTask}. However, this may be modified or replaced using |
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* subclasses of the form: |
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* |
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* <pre> |
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* public class CustomScheduledExecutor extends ScheduledThreadPoolExecutor { |
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* |
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* static class CustomTask<V> implements RunnableScheduledFuture<V> { ... } |
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* |
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* protected <V> RunnableScheduledFuture<V> decorateTask( |
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* Runnable r, RunnableScheduledFuture<V> task) { |
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* return new CustomTask<V>(r, task); |
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* } |
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* |
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* protected <V> RunnableScheduledFuture<V> decorateTask( |
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* Callable<V> c, RunnableScheduledFuture<V> task) { |
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* return new CustomTask<V>(c, task); |
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* } |
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* // ... add constructors, etc. |
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* } |
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* </pre> |
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* @since 1.5 |
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* @author Doug Lea |
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*/ |
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public class ScheduledThreadPoolExecutor |
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extends ThreadPoolExecutor |
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implements ScheduledExecutorService { |
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|
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/* |
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* This class specializes ThreadPoolExecutor implementation by |
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* |
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* 1. Using a custom task type, ScheduledFutureTask for |
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* tasks, even those that don't require scheduling (i.e., |
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* those submitted using ExecutorService execute, not |
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* ScheduledExecutorService methods) which are treated as |
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* delayed tasks with a delay of zero. |
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* |
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* 2. Using a custom queue (DelayedWorkQueue) based on an |
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* unbounded DelayQueue. The lack of capacity constraint and |
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* the fact that corePoolSize and maximumPoolSize are |
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* effectively identical simplifies some execution mechanics |
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* (see delayedExecute) compared to ThreadPoolExecutor |
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* version. |
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* |
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* The DelayedWorkQueue class is defined below for the sake of |
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* ensuring that all elements are instances of |
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* RunnableScheduledFuture. Since DelayQueue otherwise |
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* requires type be Delayed, but not necessarily Runnable, and |
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* the workQueue requires the opposite, we need to explicitly |
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* define a class that requires both to ensure that users don't |
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* add objects that aren't RunnableScheduledFutures via |
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* getQueue().add() etc. |
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* |
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* 3. Supporting optional run-after-shutdown parameters, which |
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* leads to overrides of shutdown methods to remove and cancel |
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* tasks that should NOT be run after shutdown, as well as |
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* different recheck logic when task (re)submission overlaps |
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* with a shutdown. |
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* |
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* 4. Task decoration methods to allow interception and |
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* instrumentation, which are needed because subclasses cannot |
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* otherwise override submit methods to get this effect. These |
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* don't have any impact on pool control logic though. |
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*/ |
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|
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/** |
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* 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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/** |
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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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/** |
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* 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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|
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/** Base of nanosecond timings, to avoid wrapping */ |
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private static final long NANO_ORIGIN = System.nanoTime(); |
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|
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/** |
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* Returns nanosecond time offset by origin |
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*/ |
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final long now() { |
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return System.nanoTime() - NANO_ORIGIN; |
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} |
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|
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private class ScheduledFutureTask<V> |
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extends FutureTask<V> implements RunnableScheduledFuture<V> { |
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|
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/** Sequence number to break ties FIFO */ |
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private final long sequenceNumber; |
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/** The time the task is enabled to execute in nanoTime units */ |
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private long time; |
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/** |
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* Period in nanoseconds for repeating tasks. A positive |
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* value indicates fixed-rate execution. A negative value |
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* indicates fixed-delay execution. A value of 0 indicates a |
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* non-repeating task. |
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*/ |
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private final long period; |
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|
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/** |
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* Creates a one-shot action with given nanoTime-based trigger time. |
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*/ |
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ScheduledFutureTask(Runnable r, V result, long ns) { |
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super(r, result); |
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this.time = ns; |
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this.period = 0; |
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this.sequenceNumber = sequencer.getAndIncrement(); |
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} |
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|
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/** |
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* Creates a periodic action with given nano time and period. |
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*/ |
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ScheduledFutureTask(Runnable r, V result, long ns, long period) { |
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super(r, result); |
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this.time = ns; |
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this.period = period; |
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this.sequenceNumber = sequencer.getAndIncrement(); |
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} |
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|
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/** |
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* Creates a one-shot action with given nanoTime-based trigger. |
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*/ |
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ScheduledFutureTask(Callable<V> callable, long ns) { |
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super(callable); |
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this.time = ns; |
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this.period = 0; |
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this.sequenceNumber = sequencer.getAndIncrement(); |
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} |
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|
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public long getDelay(TimeUnit unit) { |
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long d = unit.convert(time - now(), TimeUnit.NANOSECONDS); |
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return d; |
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} |
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|
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public int compareTo(Delayed other) { |
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if (other == this) // compare zero ONLY if same object |
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return 0; |
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if (other instanceof ScheduledFutureTask) { |
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ScheduledFutureTask<?> x = (ScheduledFutureTask<?>)other; |
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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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long d = (getDelay(TimeUnit.NANOSECONDS) - |
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other.getDelay(TimeUnit.NANOSECONDS)); |
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return (d == 0) ? 0 : ((d < 0) ? -1 : 1); |
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} |
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|
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/** |
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* Returns true if this is a periodic (not a one-shot) action. |
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* |
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* @return true if periodic |
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*/ |
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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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/** |
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* Sets the next time to run for a periodic task |
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*/ |
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private void setNextRunTime() { |
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long p = period; |
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if (p > 0) |
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time += p; |
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else |
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time = now() - p; |
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} |
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|
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/** |
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* Overrides FutureTask version so as to reset/requeue if periodic. |
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*/ |
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public void run() { |
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boolean periodic = isPeriodic(); |
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if (!canRunInCurrentRunState(periodic)) |
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cancel(false); |
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else if (!periodic) |
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ScheduledFutureTask.super.run(); |
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else if (ScheduledFutureTask.super.runAndReset()) { |
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setNextRunTime(); |
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reExecutePeriodic(this); |
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} |
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} |
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} |
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|
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/** |
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* Returns true if can run a task given current run state |
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* and run-after-shutdown parameters |
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* @param periodic true if this task periodic, false if delayed |
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*/ |
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boolean canRunInCurrentRunState(boolean periodic) { |
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return isRunningOrShutdown(periodic ? |
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continueExistingPeriodicTasksAfterShutdown : |
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executeExistingDelayedTasksAfterShutdown); |
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} |
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|
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/** |
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* Main execution method for delayed or periodic tasks. If pool |
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* is shut down, rejects the task. Otherwise adds task to queue |
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* and starts a thread, if necessary, to run it. (We cannot |
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* prestart the thread to run the task because the task (probably) |
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* shouldn't be run yet,) If the pool is shut down while the task |
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* is being added, cancel and remove it if required by state and |
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* run-after-shutdown parameters |
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* @param task the task |
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*/ |
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private void delayedExecute(RunnableScheduledFuture<?> task) { |
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if (isShutdown()) |
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reject(task); |
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else { |
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super.getQueue().add(task); |
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if (isShutdown() && |
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!canRunInCurrentRunState(task.isPeriodic()) && |
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remove(task)) |
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task.cancel(false); |
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prestartCoreThread(); |
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} |
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} |
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|
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/** |
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* Requeues a periodic task unless current run state precludes |
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* it. Same idea as delayedExecute except drops task rather than |
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* rejecting. |
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* @param task the task |
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*/ |
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void reExecutePeriodic(RunnableScheduledFuture<?> task) { |
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if (canRunInCurrentRunState(true)) { |
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super.getQueue().add(task); |
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if (!canRunInCurrentRunState(true) && remove(task)) |
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task.cancel(false); |
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prestartCoreThread(); |
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} |
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} |
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|
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/** |
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* Cancels and clears the queue of all tasks that should not be run |
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* due to shutdown policy. Invoked within super.shutdown. |
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*/ |
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@Override void onShutdown() { |
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BlockingQueue<Runnable> q = super.getQueue(); |
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boolean keepDelayed = |
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getExecuteExistingDelayedTasksAfterShutdownPolicy(); |
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boolean keepPeriodic = |
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getContinueExistingPeriodicTasksAfterShutdownPolicy(); |
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if (!keepDelayed && !keepPeriodic) |
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q.clear(); |
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else { |
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// Traverse snapshot to avoid iterator exceptions |
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Object[] entries = q.toArray(); |
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for (int i = 0; i < entries.length; ++i) { |
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Object e = entries[i]; |
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if (e instanceof RunnableScheduledFuture) { |
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RunnableScheduledFuture<?> t = |
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(RunnableScheduledFuture<?>)e; |
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if ((t.isPeriodic() ? !keepPeriodic : !keepDelayed) || |
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t.isCancelled()) { // also remove if already cancelled |
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if (q.remove(t)) |
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t.cancel(false); |
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} |
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} |
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} |
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} |
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} |
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|
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/** |
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* Modifies or replaces the task used to execute a runnable. |
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* This method can be used to override the concrete |
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* class used for managing internal tasks. |
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* The default implementation simply returns the given task. |
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* |
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* @param runnable the submitted Runnable |
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* @param task the task created to execute the runnable |
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* @return a task that can execute the runnable |
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* @since 1.6 |
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*/ |
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protected <V> RunnableScheduledFuture<V> decorateTask( |
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Runnable runnable, RunnableScheduledFuture<V> task) { |
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return task; |
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} |
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|
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/** |
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* Modifies or replaces the task used to execute a callable. |
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* This method can be used to override the concrete |
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* class used for managing internal tasks. |
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* The default implementation simply returns the given task. |
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* |
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* @param callable the submitted Callable |
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* @param task the task created to execute the callable |
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* @return a task that can execute the callable |
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* @since 1.6 |
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*/ |
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protected <V> RunnableScheduledFuture<V> decorateTask( |
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Callable<V> callable, RunnableScheduledFuture<V> task) { |
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return task; |
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} |
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|
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/** |
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* Creates a new ScheduledThreadPoolExecutor with the given core |
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* pool size. |
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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, unless allowCoreThreadTimeOut is set |
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* @throws IllegalArgumentException if <tt>corePoolSize < 0</tt> |
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*/ |
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public ScheduledThreadPoolExecutor(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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|
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/** |
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* Creates a new ScheduledThreadPoolExecutor with the given |
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* initial parameters. |
370 |
* |
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* @param corePoolSize the number of threads to keep in the pool, |
372 |
* even if they are idle, unless allowCoreThreadTimeOut is set |
373 |
* @param threadFactory the factory to use when the executor |
374 |
* creates a new thread |
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* @throws IllegalArgumentException if <tt>corePoolSize < 0</tt> |
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* @throws NullPointerException if threadFactory is null |
377 |
*/ |
378 |
public ScheduledThreadPoolExecutor(int corePoolSize, |
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ThreadFactory threadFactory) { |
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super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
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new DelayedWorkQueue(), threadFactory); |
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} |
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|
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/** |
385 |
* Creates a new ScheduledThreadPoolExecutor with the given |
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* initial parameters. |
387 |
* |
388 |
* @param corePoolSize the number of threads to keep in the pool, |
389 |
* even if they are idle, unless allowCoreThreadTimeOut is set |
390 |
* @param handler the handler to use when execution is blocked |
391 |
* because the thread bounds and queue capacities are reached |
392 |
* @throws IllegalArgumentException if <tt>corePoolSize < 0</tt> |
393 |
* @throws NullPointerException if handler is null |
394 |
*/ |
395 |
public ScheduledThreadPoolExecutor(int corePoolSize, |
396 |
RejectedExecutionHandler handler) { |
397 |
super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
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new DelayedWorkQueue(), handler); |
399 |
} |
400 |
|
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/** |
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* Creates a new ScheduledThreadPoolExecutor with the given |
403 |
* initial parameters. |
404 |
* |
405 |
* @param corePoolSize the number of threads to keep in the pool, |
406 |
* even if they are idle, unless allowCoreThreadTimeOut is set |
407 |
* @param threadFactory the factory to use when the executor |
408 |
* creates a new thread |
409 |
* @param handler the handler to use when execution is blocked |
410 |
* because the thread bounds and queue capacities are reached. |
411 |
* @throws IllegalArgumentException if <tt>corePoolSize < 0</tt> |
412 |
* @throws NullPointerException if threadFactory or handler is null |
413 |
*/ |
414 |
public ScheduledThreadPoolExecutor(int corePoolSize, |
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ThreadFactory threadFactory, |
416 |
RejectedExecutionHandler handler) { |
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super(corePoolSize, Integer.MAX_VALUE, 0, TimeUnit.NANOSECONDS, |
418 |
new DelayedWorkQueue(), threadFactory, handler); |
419 |
} |
420 |
|
421 |
/** |
422 |
* @throws RejectedExecutionException {@inheritDoc} |
423 |
* @throws NullPointerException {@inheritDoc} |
424 |
*/ |
425 |
public ScheduledFuture<?> schedule(Runnable command, |
426 |
long delay, |
427 |
TimeUnit unit) { |
428 |
if (command == null || unit == null) |
429 |
throw new NullPointerException(); |
430 |
if (delay < 0) delay = 0; |
431 |
long triggerTime = now() + unit.toNanos(delay); |
432 |
RunnableScheduledFuture<?> t = decorateTask(command, |
433 |
new ScheduledFutureTask<Boolean>(command, null, triggerTime)); |
434 |
delayedExecute(t); |
435 |
return t; |
436 |
} |
437 |
|
438 |
/** |
439 |
* @throws RejectedExecutionException {@inheritDoc} |
440 |
* @throws NullPointerException {@inheritDoc} |
441 |
*/ |
442 |
public <V> ScheduledFuture<V> schedule(Callable<V> callable, |
443 |
long delay, |
444 |
TimeUnit unit) { |
445 |
if (callable == null || unit == null) |
446 |
throw new NullPointerException(); |
447 |
if (delay < 0) delay = 0; |
448 |
long triggerTime = now() + unit.toNanos(delay); |
449 |
RunnableScheduledFuture<V> t = decorateTask(callable, |
450 |
new ScheduledFutureTask<V>(callable, triggerTime)); |
451 |
delayedExecute(t); |
452 |
return t; |
453 |
} |
454 |
|
455 |
/** |
456 |
* @throws RejectedExecutionException {@inheritDoc} |
457 |
* @throws NullPointerException {@inheritDoc} |
458 |
* @throws IllegalArgumentException {@inheritDoc} |
459 |
*/ |
460 |
public ScheduledFuture<?> scheduleAtFixedRate(Runnable command, |
461 |
long initialDelay, |
462 |
long period, |
463 |
TimeUnit unit) { |
464 |
if (command == null || unit == null) |
465 |
throw new NullPointerException(); |
466 |
if (period <= 0) |
467 |
throw new IllegalArgumentException(); |
468 |
if (initialDelay < 0) initialDelay = 0; |
469 |
long triggerTime = now() + unit.toNanos(initialDelay); |
470 |
RunnableScheduledFuture<?> t = decorateTask(command, |
471 |
new ScheduledFutureTask<Object>(command, |
472 |
null, |
473 |
triggerTime, |
474 |
unit.toNanos(period))); |
475 |
delayedExecute(t); |
476 |
return t; |
477 |
} |
478 |
|
479 |
/** |
480 |
* @throws RejectedExecutionException {@inheritDoc} |
481 |
* @throws NullPointerException {@inheritDoc} |
482 |
* @throws IllegalArgumentException {@inheritDoc} |
483 |
*/ |
484 |
public ScheduledFuture<?> scheduleWithFixedDelay(Runnable command, |
485 |
long initialDelay, |
486 |
long delay, |
487 |
TimeUnit unit) { |
488 |
if (command == null || unit == null) |
489 |
throw new NullPointerException(); |
490 |
if (delay <= 0) |
491 |
throw new IllegalArgumentException(); |
492 |
if (initialDelay < 0) initialDelay = 0; |
493 |
long triggerTime = now() + unit.toNanos(initialDelay); |
494 |
RunnableScheduledFuture<?> t = decorateTask(command, |
495 |
new ScheduledFutureTask<Boolean>(command, |
496 |
null, |
497 |
triggerTime, |
498 |
unit.toNanos(-delay))); |
499 |
delayedExecute(t); |
500 |
return t; |
501 |
} |
502 |
|
503 |
/** |
504 |
* Executes command with zero required delay. This has effect |
505 |
* equivalent to <tt>schedule(command, 0, anyUnit)</tt>. Note |
506 |
* that inspections of the queue and of the list returned by |
507 |
* <tt>shutdownNow</tt> will access the zero-delayed |
508 |
* {@link ScheduledFuture}, not the <tt>command</tt> itself. |
509 |
* |
510 |
* @param command the task to execute |
511 |
* @throws RejectedExecutionException at discretion of |
512 |
* <tt>RejectedExecutionHandler</tt>, if task cannot be accepted |
513 |
* for execution because the executor has been shut down. |
514 |
* @throws NullPointerException if command is null |
515 |
*/ |
516 |
public void execute(Runnable command) { |
517 |
if (command == null) |
518 |
throw new NullPointerException(); |
519 |
schedule(command, 0, TimeUnit.NANOSECONDS); |
520 |
} |
521 |
|
522 |
// Override AbstractExecutorService methods |
523 |
|
524 |
/** |
525 |
* @throws RejectedExecutionException {@inheritDoc} |
526 |
* @throws NullPointerException {@inheritDoc} |
527 |
*/ |
528 |
public Future<?> submit(Runnable task) { |
529 |
return schedule(task, 0, TimeUnit.NANOSECONDS); |
530 |
} |
531 |
|
532 |
/** |
533 |
* @throws RejectedExecutionException {@inheritDoc} |
534 |
* @throws NullPointerException {@inheritDoc} |
535 |
*/ |
536 |
public <T> Future<T> submit(Runnable task, T result) { |
537 |
return schedule(Executors.callable(task, result), |
538 |
0, TimeUnit.NANOSECONDS); |
539 |
} |
540 |
|
541 |
/** |
542 |
* @throws RejectedExecutionException {@inheritDoc} |
543 |
* @throws NullPointerException {@inheritDoc} |
544 |
*/ |
545 |
public <T> Future<T> submit(Callable<T> task) { |
546 |
return schedule(task, 0, TimeUnit.NANOSECONDS); |
547 |
} |
548 |
|
549 |
/** |
550 |
* Sets the policy on whether to continue executing existing |
551 |
* periodic tasks even when this executor has been |
552 |
* <tt>shutdown</tt>. In this case, these tasks will only |
553 |
* terminate upon <tt>shutdownNow</tt>, or after setting the |
554 |
* policy to <tt>false</tt> when already shutdown. This value is |
555 |
* by default false. |
556 |
* |
557 |
* @param value if true, continue after shutdown, else don't. |
558 |
* @see #getContinueExistingPeriodicTasksAfterShutdownPolicy |
559 |
*/ |
560 |
public void setContinueExistingPeriodicTasksAfterShutdownPolicy(boolean value) { |
561 |
continueExistingPeriodicTasksAfterShutdown = value; |
562 |
if (!value && isShutdown()) { |
563 |
onShutdown(); |
564 |
tryTerminate(); |
565 |
} |
566 |
} |
567 |
|
568 |
/** |
569 |
* Gets the policy on whether to continue executing existing |
570 |
* periodic tasks even when this executor has been |
571 |
* <tt>shutdown</tt>. In this case, these tasks will only |
572 |
* terminate upon <tt>shutdownNow</tt> or after setting the policy |
573 |
* to <tt>false</tt> when already shutdown. This value is by |
574 |
* default false. |
575 |
* |
576 |
* @return true if will continue after shutdown |
577 |
* @see #setContinueExistingPeriodicTasksAfterShutdownPolicy |
578 |
*/ |
579 |
public boolean getContinueExistingPeriodicTasksAfterShutdownPolicy() { |
580 |
return continueExistingPeriodicTasksAfterShutdown; |
581 |
} |
582 |
|
583 |
/** |
584 |
* Sets the policy on whether to execute existing delayed |
585 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
586 |
* this case, these tasks will only terminate upon |
587 |
* <tt>shutdownNow</tt>, or after setting the policy to |
588 |
* <tt>false</tt> when already shutdown. This value is by default |
589 |
* true. |
590 |
* |
591 |
* @param value if true, execute after shutdown, else don't. |
592 |
* @see #getExecuteExistingDelayedTasksAfterShutdownPolicy |
593 |
*/ |
594 |
public void setExecuteExistingDelayedTasksAfterShutdownPolicy(boolean value) { |
595 |
executeExistingDelayedTasksAfterShutdown = value; |
596 |
if (!value && isShutdown()) { |
597 |
onShutdown(); |
598 |
tryTerminate(); |
599 |
} |
600 |
} |
601 |
|
602 |
/** |
603 |
* Gets the policy on whether to execute existing delayed |
604 |
* tasks even when this executor has been <tt>shutdown</tt>. In |
605 |
* this case, these tasks will only terminate upon |
606 |
* <tt>shutdownNow</tt>, or after setting the policy to |
607 |
* <tt>false</tt> when already shutdown. This value is by default |
608 |
* true. |
609 |
* |
610 |
* @return true if will execute after shutdown |
611 |
* @see #setExecuteExistingDelayedTasksAfterShutdownPolicy |
612 |
*/ |
613 |
public boolean getExecuteExistingDelayedTasksAfterShutdownPolicy() { |
614 |
return executeExistingDelayedTasksAfterShutdown; |
615 |
} |
616 |
|
617 |
/** |
618 |
* Initiates an orderly shutdown in which previously submitted |
619 |
* tasks are executed, but no new tasks will be accepted. If the |
620 |
* <tt>ExecuteExistingDelayedTasksAfterShutdownPolicy</tt> has |
621 |
* been set <tt>false</tt>, existing delayed tasks whose delays |
622 |
* have not yet elapsed are cancelled. And unless the |
623 |
* <tt>ContinueExistingPeriodicTasksAfterShutdownPolicy</tt> has |
624 |
* been set <tt>true</tt>, future executions of existing periodic |
625 |
* tasks will be cancelled. |
626 |
*/ |
627 |
public void shutdown() { |
628 |
super.shutdown(); |
629 |
} |
630 |
|
631 |
/** |
632 |
* Attempts to stop all actively executing tasks, halts the |
633 |
* processing of waiting tasks, and returns a list of the tasks |
634 |
* that were awaiting execution. |
635 |
* |
636 |
* <p>There are no guarantees beyond best-effort attempts to stop |
637 |
* processing actively executing tasks. This implementation |
638 |
* cancels tasks via {@link Thread#interrupt}, so any task that |
639 |
* fails to respond to interrupts may never terminate. |
640 |
* |
641 |
* @return list of tasks that never commenced execution. Each |
642 |
* element of this list is a {@link ScheduledFuture}, |
643 |
* including those tasks submitted using <tt>execute</tt>, which |
644 |
* are for scheduling purposes used as the basis of a zero-delay |
645 |
* <tt>ScheduledFuture</tt>. |
646 |
* @throws SecurityException {@inheritDoc} |
647 |
*/ |
648 |
public List<Runnable> shutdownNow() { |
649 |
return super.shutdownNow(); |
650 |
} |
651 |
|
652 |
/** |
653 |
* Returns the task queue used by this executor. Each element of |
654 |
* this queue is a {@link ScheduledFuture}, including those |
655 |
* tasks submitted using <tt>execute</tt> which are for scheduling |
656 |
* purposes used as the basis of a zero-delay |
657 |
* <tt>ScheduledFuture</tt>. Iteration over this queue is |
658 |
* <em>not</em> guaranteed to traverse tasks in the order in |
659 |
* which they will execute. |
660 |
* |
661 |
* @return the task queue |
662 |
*/ |
663 |
public BlockingQueue<Runnable> getQueue() { |
664 |
return super.getQueue(); |
665 |
} |
666 |
|
667 |
/** |
668 |
* An annoying wrapper class to convince javac to use a |
669 |
* DelayQueue<RunnableScheduledFuture> as a BlockingQueue<Runnable> |
670 |
*/ |
671 |
private static class DelayedWorkQueue |
672 |
extends AbstractCollection<Runnable> |
673 |
implements BlockingQueue<Runnable> { |
674 |
|
675 |
private final DelayQueue<RunnableScheduledFuture> dq = new DelayQueue<RunnableScheduledFuture>(); |
676 |
public Runnable poll() { return dq.poll(); } |
677 |
public Runnable peek() { return dq.peek(); } |
678 |
public Runnable take() throws InterruptedException { return dq.take(); } |
679 |
public Runnable poll(long timeout, TimeUnit unit) throws InterruptedException { |
680 |
return dq.poll(timeout, unit); |
681 |
} |
682 |
|
683 |
public boolean add(Runnable x) { |
684 |
return dq.add((RunnableScheduledFuture)x); |
685 |
} |
686 |
public boolean offer(Runnable x) { |
687 |
return dq.offer((RunnableScheduledFuture)x); |
688 |
} |
689 |
public void put(Runnable x) { |
690 |
dq.put((RunnableScheduledFuture)x); |
691 |
} |
692 |
public boolean offer(Runnable x, long timeout, TimeUnit unit) { |
693 |
return dq.offer((RunnableScheduledFuture)x, timeout, unit); |
694 |
} |
695 |
|
696 |
public Runnable remove() { return dq.remove(); } |
697 |
public Runnable element() { return dq.element(); } |
698 |
public void clear() { dq.clear(); } |
699 |
public int drainTo(Collection<? super Runnable> c) { return dq.drainTo(c); } |
700 |
public int drainTo(Collection<? super Runnable> c, int maxElements) { |
701 |
return dq.drainTo(c, maxElements); |
702 |
} |
703 |
|
704 |
public int remainingCapacity() { return dq.remainingCapacity(); } |
705 |
public boolean remove(Object x) { return dq.remove(x); } |
706 |
public boolean contains(Object x) { return dq.contains(x); } |
707 |
public int size() { return dq.size(); } |
708 |
public boolean isEmpty() { return dq.isEmpty(); } |
709 |
public Object[] toArray() { return dq.toArray(); } |
710 |
public <T> T[] toArray(T[] array) { return dq.toArray(array); } |
711 |
public Iterator<Runnable> iterator() { |
712 |
return new Iterator<Runnable>() { |
713 |
private Iterator<RunnableScheduledFuture> it = dq.iterator(); |
714 |
public boolean hasNext() { return it.hasNext(); } |
715 |
public Runnable next() { return it.next(); } |
716 |
public void remove() { it.remove(); } |
717 |
}; |
718 |
} |
719 |
} |
720 |
} |