From the official docs: "The Arduino programming language is an implementation of Wiring, a similar physical computing platform, which is based on the Processing multimedia programming environment." and "the Arduino language is merely a set of C/C++ functions that can be called from your code."

Just saw this, but please note that Processing is not being run on the Arduino, but rather it is controlling the Arduino through the serial connection. And you can control an Arduino via a serial connection using just about any programming language, including Python and JavaScript.

So again, you can't run Java or Processing on the Arduino. Keep researching.