import java.awt.event.*;

class GestoreFinestra implements WindowListener {
    public void windowIconified(WindowEvent e) {}
    public void windowDeiconified(WindowEvent e) {}
    public void windowActivated(WindowEvent e) {}
    public void windowDeactivated(WindowEvent e) {}
    public void windowOpened(WindowEvent e) {}
    public void windowClosed(WindowEvent e) {}
    public void windowClosing(WindowEvent e) {
...
        System.exit(0);
    }
}