java.util
Class TimerTask

java.lang.Object
  java.util.TimerTask

All Implemented Interfaces:

Runnable

Direct Known Subclasses:

ReassemblyExpiration, RetransmitTimer

public abstract class TimerTask
extends Object
implements Runnable

A task that can be scheduled for one-time or repeated execution by a Timer.

Since:

1.3

Version:

1.5, 12/04/99

Author:

Josh Bloch

See Also:

Timer

Constructor Summary

protected

TimerTask() Creates a new timer task.

Method Summary

boolean	cancel() Cancels this timer task.
abstract void	run() The action to be performed by this timer task.
long	scheduledExecutionTime() Returns the scheduled execution time of the most recent actual execution of this task.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TimerTask

protected TimerTask()

Creates a new timer task.

Method Detail

cancel

public boolean cancel()

Cancels this timer task. If the task has been scheduled for one-time execution and has not yet run, or has not yet been scheduled, it will never run. If the task has been scheduled for repeated execution, it will never run again. (If the task is running when this call occurs, the task will run to completion, but will never run again.)

Note that calling this method from within the run method of a repeating timer task absolutely guarantees that the timer task will not run again.

This method may be called repeatedly; the second and subsequent calls have no effect.

Returns:

true if this task is scheduled for one-time execution and has not yet run, or this task is scheduled for repeated execution. Returns false if the task was scheduled for one-time execution and has already run, or if the task was never scheduled, or if the task was already cancelled. (Loosely speaking, this method returns true if it prevents one or more scheduled executions from taking place.)

run

public abstract void run()

The action to be performed by this timer task.

Specified by:

run in interface Runnable

See Also:

Thread.run()

scheduledExecutionTime

public long scheduledExecutionTime()

Returns the scheduled execution time of the most recent actual execution of this task. (If this method is invoked while task execution is in progress, the return value is the scheduled execution time of the ongoing task execution.)

This method is typically invoked from within a task's run method, to determine whether the current execution of the task is sufficiently timely to warrant performing the scheduled activity:

   public void run() {
       if (System.currentTimeMillis() - scheduledExecutionTime() >=
           MAX_TARDINESS)
               return;  // Too late; skip this execution.
       // Perform the task
   }
 

This method is typically not used in conjunction with fixed-delay execution repeating tasks, as their scheduled execution times are allowed to drift over time, and so are not terribly significant.

Returns:

the time at which the most recent execution of this task was scheduled to occur, in the format returned by Date.getTime(). The return value is undefined if the task has yet to commence its first execution.

See Also:

Date.getTime()