Timer

Links

Stopping Timer Threads

By default, a program keeps running as long as its timer threads are running. You can terminate a timer thread in four ways:

Invoke cancel on the timer. You can do this from anywhere in the program, such as from a timer task’s run method.
Make the timer’s thread a “daemon” by creating the timer like this: new Timer(true). If the only threads left in the program are daemon threads, the program exits.
After all the timer’s scheduled tasks have finished executing, remove all references to the Timer object. Eventually, the timer’s thread will terminate.
Invoke the System.exit method, which makes the entire program (and all its threads) exit.

Sample

Standard Repeat

A Maven 2 project can be checked out from Subversion on:

http://g1/svn/home/patrick/learn/timer-example/

package com.mycompany.example;

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

public final class TimerExample extends TimerTask {

    /** Number of millseconds - 5 seconds. */
    private static final long DELAY_IN_MILLISECONDS = 5000;

    /** Timer to make sure all errors are reported. */
    private Timer timer = null;

    /** Create the timer - which will make repeated calls to run(). */
    public void createTimer() {
        if (timer == null) {
            timer = new Timer(true);
            timer.scheduleAtFixedRate(this, DELAY_IN_MILLISECONDS, DELAY_IN_MILLISECONDS);
        }
    }

    /** This function will be called by the timer object at the specified interval */
    public void run() {
        System.out.println("run()");
    }
}

The associated unit test:

package com.mycompany.example;

import junit.framework.TestCase;

public class TimerExampleTest extends TestCase {
    public void testTimer() throws InterruptedException {
        TimerExample timer = new TimerExample();
        timer.createTimer();
        Thread.sleep(30000);
    }
}

Simple Repeat

Scheduling a Timer Task to Run Repeatedly

int delay = 5000;   // delay for 5 sec.
int period = 1000;  // repeat every sec.

Timer timer = new Timer(true);

timer.scheduleAtFixedRate(new TimerTask() {
        public void run() {
            // Task here ...
        }
    }, delay, period);

Specific Time

Scheduling a Timer Task to Run at a Certain Time

int numberOfMillisecondsInTheFuture = 10000; // 10 sec
Date timeToRun = new Date(System.currentTimeMillis() + numberOfMillisecondsInTheFuture);

Timer timer = new Timer(true);

timer.schedule(new TimerTask() {
        public void run() {
            // Task here ...
        }
    }, timeToRun)