Method windowClosing

StickyNotes/src/com/dosse/stickynotes/Note.java:232–237

(WindowEvent e)

        setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE); //if alt+f4 is pressed, this will cause the windowClosing event to be fired
        addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                //if alt+f4 is pressed, save the current state and terminate the app
                Main.saveState();
                System.exit(0);
            }
        });
        addWindowFocusListener(new WindowAdapter() {
            @Override