In the case the OP didn't realize, Java underlies Processing and C++ is underneath Arduino.
I would be starting from scratch learning both the Arduino and the other so I would think C++ would be a bit nicer as it would be only one language to learn, but most people it seems use Java for GUI and such.
Yep, already got that (sorta vague in my post). Good to have it spelt out plain and simple though for others.
Thanks.