How to avoid swing program exit

Question

My application, while in a specific condition, need to avoid program exit. In my application program exit can be done:
- through a menu bar menu item (exit): no problem to avoid exiting, I manage it with success.
- by clicking the standard red button in the applcation title bar (in other words the standard close button): here I need your help since I didnt' found a way to avoid the program closure.
To be clear, my application should avoid ( I mean avoid not delay) it's closure when is communicating (throgh RS232C connection) with other external devices, infact when the user select the exit item in main menù the application show a warning dialog with the mesage "you connot exit now, wait communication end". But I don't fiond a way to do the same whit close button, I can do something (i.e. showing the warnign dialog) creating a listener but I cannot "consume" the event so I'm not able to avoid the program exit.
Do you know a way to do it?
Thanks a lot for your help.

Answer 1

I tried with setDefaultCloseOperation(...) but seems have no effect one exit (exit in any case). I don't know if is a matter of SingleFrameApplication implementation (that I use since my project is crated with NetBeans swing wizard).
In any case at the end I found success using the SingleFrameApplication ExitListener interface, hereafter my solution (that works correctly):
public class FuelFEPApp extends SingleFrameApplication {
    class ConfirmExit implements ExitListener
        public boolean canExit(java.util.EventObject e)
            boolean result= false;
            if (mainThread.areChannelsCommunicating())
                // There are communications running, avoid exit...
                Object source = (e != null) ? e.getSource() : null;
                Component owner = (source instanceof Component) ? (Component)source : null;
                JOptionPane.showMessageDialog(owner,
                                              (Object)"Communications running, you cannot exit application",
                                              "Warning",
                                              JOptionPane.WARNING_MESSAGE);
            else
                // No communications then exit
                result= true;
            return result;
        public void willExit(java.util.EventObject e)
    @Override protected void startup() {
        FEPView= new FuelFEPView(this);
        show(FEPView);
        this.addExitListener(new ConfirmExit());
...