Warning: this video is old, lengthy, poorly paced and rather dull so feel free to click ahead. Still, it demonstrates a reasonably complicated Swing application that looks somewhat like a native Mac OS X application. The video was put together around 2003 so the look and feel is pretty dated. But the interface is fairly complicated and it does get feedback to the customer as soon as they get data out of range, etc.

https://youtu.be/r_lTGoTscos