Tabbedpanes, hotkeys and 3 states
The underline property (taken from Tk) when set for a button, registers the meta(alt) key for that character with the form.
So pressing M-key will fire that button. This is working on tabbedpanes.
Also, a selected pane button displays in reverse video, the focussed one is BOLD, and unfocussed one NORMAL.
Following is a screenshot.
The underline tag/property (inspired by Tk) can be a pain at times, since the user does not know a button is involved. The java way of using an ampersand before the hotkey, may be better and involve lesser typing. I am thinking of going that way.