How to programmatically close a JFrame

Question

If you want the GUI to behave as if you clicked the X close button then you need to dispatch a window closing event to the Window. The ExitAction from Closing An Application allows you to add this functionality to a menu item or any component that uses Actions easily.

frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));

setVisible(false); //you can't see me!
dispose(); //Destroy the JFrame object

Not too tricky.

If by Alt-F4 or X you mean "Exit the Application Immediately Without Regard for What Other Windows or Threads are Running", then System.exit(...) will do exactly what you want in a very abrupt, brute-force, and possibly problematic fashion.

If by Alt-F4 or X you mean hide the window, then frame.setVisible(false) is how you "close" the window. The window will continue to consume resources/memory but can be made visible again very quickly.

If by Alt-F4 or X you mean hide the window and dispose of any resources it is consuming, then frame.dispose() is how you "close" the window. If the frame was the last visible window and there are no other non-daemon threads running, the program will exit. If you show the window again, it will have to reinitialize all of the native resources again (graphics buffer, window handles, etc).

dispose() might be closest to the behavior that you really want. If your app has multiple windows open, do you want Alt-F4 or X to quit the app or just close the active window?

The Java Swing Tutorial on Window Listeners may help clarify things for you.

If you have done this to make sure the user can't close the window:

frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

Then you should change your pullThePlug() method to be

public void pullThePlug() {
    // this will make sure WindowListener.windowClosing() et al. will be called.
    WindowEvent wev = new WindowEvent(this, WindowEvent.WINDOW_CLOSING);
    Toolkit.getDefaultToolkit().getSystemEventQueue().postEvent(wev);

    // this will hide and dispose the frame, so that the application quits by
    // itself if there is nothing else around. 
    setVisible(false);
    dispose();
    // if you have other similar frames around, you should dispose them, too.

    // finally, call this to really exit. 
    // i/o libraries such as WiiRemoteJ need this. 
    // also, this is what swing does for JFrame.EXIT_ON_CLOSE
    System.exit(0); 
}

I found this to be the only way that plays nice with the WindowListener and JFrame.DO_NOTHING_ON_CLOSE.