Exception during event processing

Question

I have an application which has an "exception catcher" at the bottom that performs some "exit work" that I need done when the program terminates abnormally.
In certain places of the program, I automatically have the program quit and exit by dividing by zero to trigger an exception. Up until today, this technique has worked nicely.
Today, however, I tried to do it in the middle of an AWT Event (a menu selection from a frame), in the following method:
public void actionPerformed(ActionEvent event)
Instead of the exception being handled by my routine, the program instead hangs without getting to the "catch" command that I usually use and instead generates the following sequence of error messages:
Exception occurred during event dispatching:
java.lang.ArithmeticException: / by zero
at WTPFrame.actionPerformed(wtp.java:5335)
at java.awt.AWTEventMulticaster.actionPerformed(Unknown Source)
at java.awt.MenuItem.processActionEvent(Unknown Source)
at java.awt.MenuItem.processEvent(Unknown Source)
at java.awt.MenuComponent.dispatchEventImpl(Unknown Source)
at java.awt.MenuComponent.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
Is there any thing I can do to allow this exception to pass through to my handler so that the program doesn't hang?
Thanks,
Bruce

Answer 1

When I was describing the business of subclassing an exception, this was independent of your hanging problem.
The hanging thing is a consequence of the way that threading is done in a GUI application.
Your app (by the sound of it) has two threads of execution running. The "main" thread is listening to the socket and running the game. The "EventDispatcher" thread is listening to the mouse and keyboard and redrawing the GUI.
When a GUI event handler is called, this call is done by the event dispatcher thread. If you throw an exception from the handler, the loop in the event dispatcher thread just prints the stack trace and goes on listening for more mouse and keyboard events.
To get the threads to communicate, you need for one thread to set a flag that the other thread can read. To interrupt the socket read, you need to call interrupt on the main thread from the gui thread. Lastly, to get the app to exit you must call System.exit().
class Foo {
  volatile boolean weHaveToExit = false;
  Thread mainThread;
  // this method is called when the user clicks the exit button
  void exitMenuHandler() {
    weHaveToExit = true;
    mainThread.interrupt();
  public static void main(String[] av) {
    mainThread = Thread.currentThread();
    // create the menu
    // attach the event handler to it
     while(!weHaveToExit) {
         // process a game move
     System.exit(0);