SwingWorker in Applet

Question

Hi,
I have a question on using class SwingWorker and Applets.
My usecase is this:
I have an applet with a menue (java.awt.Choice). My applet implements ItemListener and so I can register
the applet as itemlistener for the menue.
I have an inner class in the applet which extends SwingWorker. This worker is constantly running in the background - when the user
makes a choice in the menu, the worker is notified and some logic is carried out.
I need the worker to be constantly running in the background. So, in method done() - the last thing I do is to re-instantiate the worker itself.
Is this ok? Code below:
public class myapplet ....{
      private MyWorker worker;
      init(){
           worker = new MyWorker();
     class MyWorker extends SwingWorker....{
          protected String doInBackground(){
              while(true){
                 if(userMadeChoiceInTheMenu()){
                      return "someValue";             
          public void done(){
               try{
                   showNewPageBasedOnUsersChoiceInTheMenue();
               finally{
                    worker = new MyWorker();
                   worker.execute();
}best regards, Håkan
Edited by: 933709 on Jul 11, 2012 1:06 AM
Edited by: 933709 on Jul 11, 2012 1:07 AM

Answer 1

First, best practices guides exists to be followed, they prevent you from getting strange errors like this one you got.
I'll not enumerate your mistakes here, I'll just try to help you, but you should really try to follow some coding rules.
The problem could be this:
There is no guarantee that your objects will be collected at the end of your applet, or if the user reload the page, or even if he closes the tab and open another.
Calling System.gc() just asks kindly to the garbage collector, but it will probably not run.
What does it have to do with your applet?
Let's take a look:
public abstract class SwingWorker<T, V> implements Runnable, Future<T> {    
    private static ExecutorService executorService = null;This code will run only when your class is loaded the first time. Considering that it's still in the memory when the page is reloaded, it will not be executed and your old ExecutorService will be used instead of a new one, and it could will be in an illegal state!
Holp it helps,
Henrique Abreu