This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
The windowClosed event is fired when the window has already closed. But it will not close if you allow it to close. You can do this by setting a proper default close operation. When you click the X it will fire the windowClosing event instead.
Because you may want to be informed of both when the window is about to be closed (windowClosing), perhaps so you can block it, and when the window is actually closed (windowClosed), perhaps so you can do some clean-up.