Yes, for the figure the mouseOver event is ignored.
No, for the button the mouseOver event changes the mouse pointer from an arrow to a hand. (Some browsers don't do this.)
A GUI program consists of three types of software:
You get graphical components by constructing Swing objects. Listener methods and application methods are Java methods that you write. You have already written application methods: they are just ordinary Java methods that perform useful computations.
Your web browser has components (such as the "back" and "forward" buttons), listener methods that receive events (such as a click on the "back" button) and application methods that do useful things (such as moving back one page.)
To write a GUI application, keep the three types software separated (while keeping the big picture in mind.) In a big software project an entire team of programmers is assigned to each of the tasks.