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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package com.sun.tools.visualvm.core.scheduler;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Logger;
/**
* An interval based scheduler service
* Used to execute various tasks at the predefined interval
* There is supposed to be only one instance of this class accesible vie <code>getSharedInstance()</code>
* @author Jaroslav Bachorik
*/
public class Scheduler {
//~ Static fields/initializers -----------------------------------------------------------------------------------------------
private static final Logger LOGGER = Logger.getLogger(Scheduler.class.getName());
private static final Scheduler INSTANCE = new Scheduler();
//~ Instance fields ----------------------------------------------------------------------------------------------------------
private final ExecutorService immediateTaskService = Executors.newCachedThreadPool();
//~ Constructors -------------------------------------------------------------------------------------------------------------
private Scheduler() {
}
//~ Methods ------------------------------------------------------------------------------------------------------------------
/**
* Singleton accessor
* @return Returns the shared instance of scheduler service
*/
public static final Scheduler sharedInstance() {
return INSTANCE;
}
/**
* Schedules a new task to be executed with the given interval
* The newly scheduled task is exeucted out-of-order at the moment of scheduling it
* This operation's result should be cached by the caller;otherwise the task will get unscheduled immediately
* @param task The task to be executed
* @param interval The interval to execute the task
* @return Returns an instance of <code>ScheduledTask</code> that can be used to later modify the interval of execution
*/
public final ScheduledTask schedule(SchedulerTask task, Quantum interval) {
return schedule(task, interval, true);
}
/**
* Schedules a new task to be executed with the given interval
* This operation's result should be cached by the caller;otherwise the task will get unscheduled immediately
* @param task The task to be executed
* @param interval The interval to execute the task
* @param immediate Tells whether the newly scheduled task is exeucted out-of-order at the moment of scheduling it
* @return Returns an instance of <code>ScheduledTask</code> that can be used to later modify the interval of execution
*/
public final ScheduledTask schedule(final SchedulerTask task, final Quantum interval, boolean immediate) {
boolean suspended = interval.equals(Quantum.SUSPENDED);
if (immediate && !suspended) {
immediateTaskService.submit(new Runnable() {
public void run() {
task.onSchedule(System.currentTimeMillis());
}
});
}
DefaultScheduledTask scheduled = new DefaultScheduledTask(interval, task);
return scheduled;
}
/**
* Unschedules an instance of <code>Scheduled</code> class
* @param task The task to be unscheduled
*/
public final void unschedule(final ScheduledTask task) {
if (task == null) return;
task.suspend();
}
}