How to cancel a Timer from inside a TimerTask ?

Question

I have a web application with this structure:
Tomcat starts a servlet and that starts a master thread to run once every 10 minutes,
that master thread in turn starts any number of individual tasks to run until completion,
the idea being a "shoot and forget" methodology.
public class MasterTask extends TimerTask {
// run once every 10 minutes
// retrieve a list of actions to do, this is from a database, could be 10 could be 100
// for each action schedule a TimerTask
// the reason for using a new Timer each time is that any of the action tasks
// may take a long time or not, i do not want an individual task to wait
// for a previous one to finish, therefore each task is put on it's own timer
// also in order to spread resources somewhat there is an incremental delay
// so the is some time between the start of each task as there can be many
Timer timeit;
int delay = 0;
for ( ActionTask doit : taskList ) {
timeit = new Timer();
timeit(doit,delay);
delay = delay+200;
public class ActionTask extends TimerTask {
// perform whatever actions need to be done inside this individual TimerTask
// at some point the individual task has completed it's work
// how do i completely remove it from this location ?
I know that inside the TimerTask i can call cancel() but that will only prevent it from running again it does not actually remove it completely, it remains in existence and therefore uses up memory. What i need to do is call the cancel() method on the Timer in order to remove both the Timer and TimerTask.
If i do not do this then the program will just keep creating new Timers until eternity.
( or basically until i run out of memory )
How do i call the Timer.cancel() method from INSIDE the TimerTask ?
( Note that both classes are seperate classes/files and not inside the same file or class. )
thanks,
Erik
Edited by: Datapunter on Jul 27, 2009 4:06 PM

Answer 1

Gotcha,
the Timer does get cancelled but the TimerTask runs to completion first.
Was expecting a kill() type effect but that is not what cancel() does.
Servlet started by Tomcat
package servlet;
import java.util.*;
import javax.servlet.ServletException;
public class TestServlet extends javax.servlet.http.HttpServlet implements javax.servlet.Servlet {
    public void init() throws ServletException {
          Timer timeIt = new Timer();
          timeIt.schedule(new timertasks.testmaster(), 0, 10000); // every 10 seconds
}master task runs every 10 seconds indefinetly,
and every 10 seconds it starts (kicks off) 2 new tasks.
package timertasks;
import java.util.Timer;
import java.util.TimerTask;
public class testmaster extends TimerTask {
     public testmaster() {}
     // scheduled to run once every 10 seconds
     public void run() {
          int delay = 0;
          Timer timeit;
          for ( int count = 0; count < 2 ; count++ ) {
               timeit = new Timer();
               timeit.schedule(new ActionTask(timeit), delay, 2000);     // every 2 seconds
               delay = delay + 200;
}individual timertask, just comment out the timeit.cancel(); to see the difference in effect.
package timertasks;
import java.util.Timer;
import java.util.TimerTask;
public class ActionTask extends TimerTask {
     private Timer timeit;
     private int runcounter = 0;
     public ActionTask(Timer timeit) {
          this.timeit = timeit;
     // without cancel then values of runcounter should keep rising and more and more tasks should appear
     // with cancel each should run only once
     public void run() {
          System.out.println("before cancel, runcounter="+runcounter);
          timeit.cancel();
          System.out.println("after cancel, runcounter="+runcounter);
          runcounter++;
}thanks.