How to create a button group in the toolbar?

[sputnik3000]

I want to have a button group on the toolbar which can have one option be selected by the user between options A, B, C, and D. The toolbar button for the option would then be highlighted to show the user that this is the option he/she has chosen. This would be analogous to the radio buttons feature for Java Swing.

Ideally, it would be like the selection between the mouse controls in this section of the toolbar. I'm wondering if this is possible with only the plugin (no modifying the source code).

[Puybaret]

The existing buttons you mentioned are instances of JToggleButton, but you can also use JRadioButton instances gathered with Group class.
It's feasible with a plugin but I wouldn't recommend it.