Tuesday 15 March 2016

Java Timer and TimerTask – Reminder Class

Timer:
java.util.Timer is a utility class that provides facility for threads to schedule tasks for future execution in a background thread. Tasks may be scheduled for one-time execution, or for repeated execution at regular intervals.

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

java.util.TimerTask is an abstract class that implements Runnable interface and we need to extend this class to create our own TimerTask that can be scheduled using java Timer class.

Run a reminder timer task after a certain time period

import java.util.Timer;
import java.util.TimerTask;

public class TimerTaskExample {
     Timer timer;

     public TimerTaskExample(int seconds) {
           timer = new Timer();
           long millis = seconds * 1000;
           timer.schedule(new TaskReminder(), millis);
     }

     class TaskReminder extends TimerTask {
           public void run() {
                System.out.println("Timer Task is executing..!");
                /*
                 * TimerTask.cancel() method is used to
                 * terminate the Time Task.
                 */
                timer.cancel();
                System.out.println("Timer Task Finished..!");
           }
     }

     public static void main(String args[]) {
           System.out.println("Timer Task scheduled");
           int reminder_time = 3;
           new TimerTaskExample(reminder_time);
           System.out.println("It will execute after 3 sec...");
     }
}

Output:
Timer Task scheduled
It will execute after 3 sec...
Timer Task is executing..!
Timer Task Finished..!

Perform timer task repeatedly

import java.util.Timer;
import java.util.TimerTask;

public class RepeatTimerTaskExam {
     Timer timer;

     public RepeatTimerTaskExam(long intialDelay,long subsequentRate){
           timer = new Timer();

           timer.schedule(new TaskReminder(),intialDelay,subsequentRate);
     }

     class TaskReminder extends TimerTask {
           int loop = 5;

           public void run() {
                if (loop > 0) {
                     System.out.println("Timer task, Repeat# "+ loop);
                     loop--;
                } else {
                     timer.cancel();
                     System.out.println("Timer task.. Finished!");
                }
           }
     }

     public static void main(String args[]) {
           long intialDelay = 0; // time to start first Task
           long subsequentRate = 1000; // delay subsequent Task.
          
           new RepeatTimerTaskExam(intialDelay, subsequentRate);
           System.out.println("Task scheduled...");
     }
}
Output:
Task scheduled...
Timer task, Repeat# 5
Timer task, Repeat# 4
Timer task, Repeat# 3
Timer task, Repeat# 2
Timer task, Repeat# 1
Timer task.. Finished!

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