Problem with a Timer (Java.util)

Question

Hello guys,
I have a small problem with Java timer. The problem is I wanne do some task let's say after 5 seconds, so I created a timer and set its delay to 5000 milli seconds and run my program to see that the task is well performed but the program doesn't end. I tried the timer.cancel() method or tried to assign it to null.... but never works.
So how do i make the program stop gracefully after the scheduled task finishes.
My Code...
int delay = 5000;  
          timer = new Timer();
          //timer.schedule(task, delay)
          final boolean flag =true;
          timer.schedule(new TimerTask() {
               public void run() {
                    System.out.println("hello");       // the program is still waiting after executing this.... why?
          }, delay);
          // timer.cancel();     
          System.out.println("ccc"); // these two are printed gracefully before the scheduled task... that's good.
          System.out.println("ddd");So any idea on how to solve this problem... make the timer stop after executing the required task.
Thanks in advance

Answer 1

Have a read of the JavaDocs, someone went to great lengths to write these to save you headaches like this.
http://java.sun.com/j2se/1.5.0/docs/api/java/util/Timer.html
Have a play around with this code un-commenting the cancel, runTimerInDifferentScope and garbage collection call to see how it behaves each time.
import java.util.Timer;
import java.util.TimerTask;
public class TimerExample {
     public static void main(String[] args) {
          final Timer timer = new Timer();
          timer.schedule(new TimerTask() {
               @Override
               public void run() {
                    System.out.println("[A] After 1 second!");
                    //timer.cancel();
          }, 1000);
          System.out.println("[A]");
          //runTimerInDifferentScope();
          //System.gc();
     private static void runTimerInDifferentScope() {
          final Timer timer = new Timer();
          timer.schedule(new TimerTask() {
               @Override
               public void run() {
                    System.out.println(" After 1 second!");
                    //No need to cancel me, I will be garbage collected
          }, 1000);
          System.out.println("[B]");
Forgot to mention that the call to System.gc() was necessary to clear the timer. This is not something you should depend on (the garbage collector) in your application. I used it in this example because it's likely it would never run with such a small program and plenty of heap space left. If in doubt then use timer.cancel() as with the first example.
Edited by: michael- on Dec 15, 2009 12:42 PM