Timer and TimerTask work together. Timer is the class that you will use to schedule a task for execution. The task being scheduled must be an instance of TimerTask. Thus, to schedule a task, you will first create a TimerTask object and then schedule it for execution using an instance of Timer
TimerTask implements the Runnable interface; thus, it can be used to create a thread of execution. Its constructor is shown here:
TimerTask( )
The Methods Defined by TimerTask
| Method | Description | |
| boolean cancel( ) | Terminates the task. Returns true if an execution of the task is | |
| prevented. Otherwise, returns false. | ||
| abstract void run( ) | Contains the code for the timer task. | |
| long scheduledExecutionTime( ) | Returns the time at which the last execution of the task was | |
| scheduled to have occurred. |
| Method | Description | |
| void cancel( ) | Cancels the timer thread. | |
| int purge( ) | Deletes cancelled tasks from the timer’s queue. | |
| void schedule(TimerTask TTask, | TTask is scheduled for execution after the period passed | |
| long wait) | in wait has elapsed. The wait parameter is specified in | |
| milliseconds. | ||
| void schedule(TimerTask TTask, | TTask is scheduled for execution after the period passed | |
| long wait, long repeat) | in wait has elapsed. The task is then executed repeatedly | |
| at the interval specified by repeat. Both wait and repeat | ||
| are specified in milliseconds. | ||
| void schedule(TimerTask TTask, | TTask is scheduled for execution at the time specified | |
| Date targetTime) | by targetTime. | |
| void schedule(TimerTask TTask, | TTask is scheduled for execution at the time specified | |
| Date targetTime, | by targetTime. The task is then executed repeatedly at | |
| long repeat) | the interval passed in repeat. The repeat parameter is | |
| specified in milliseconds. | ||
| void scheduleAtFixedRate( | TTask is scheduled for execution after the period passed | |
| TimerTask TTask, | in wait has elapsed. The task is then executed repeatedly | |
| long wait, long repeat) | at the interval specified by repeat. Both wait and repeat | |
| are specified in milliseconds. The time of each repetition is | ||
| relative to the first execution, not the preceding execution. | ||
| Thus, the overall rate of execution is fixed. | ||
| void scheduleAtFixedRate( | TTask is scheduled for execution at the time specified | |
| TimerTask TTask, | by targetTime. The task is then executed repeatedly at | |
| Date targetTime, | the interval passed in repeat. The repeat parameter is | |
| long repeat) | specified in milliseconds. The time of each repetition is | |
| relative to the first execution, not the preceding execution. | ||
| Thus, the overall rate of execution is fixed. |
Demonstrate Timer and TimerTask
import java.util.*;
class MyTimerTask extends TimerTask {
public void run() { System.out.println("Timer task executed.");
}
}
class TTest {
public static void main(String args[]) { MyTimerTask myTask = new MyTimerTask(); Timer myTimer = new Timer();
/* Set an initial delay of 1 second,
then repeat every half second.
*/
myTimer.schedule(myTask, 1000, 500);
try { Thread.sleep(5000);
}catch (InterruptedException exc) {}
myTimer.cancel();
}
}