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.)
Of course, when you click the button this is another kind of event, and is not ignored, either.
A GUI program consists of three types of software:
The graphical components are Swing objects. You either use then as they are defined or extend them into your own classes. Listener methods and application methods are Java methods that you write. Listener methods respond to events by calling application methods. Application methods are ordinary Java methods that perform useful computations. They receive data from the GUI and send data to the GUI to be displayed, but are not usually themselves conderned with the user interface.
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 or forward 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.