In the Game Development program at RIT we take a course titled Interactive Media Development. The first half of this course uses the Processing Framework in order to focus more on the development of AI as opposed to the graphical backend. The book that is referenced for this course is The Nature of Code by Daniel Shiffman.
In chapter 5 of The Nature of Code Shiffman covers using physics libraries in conjunction with processing for more realistic simulations. One of the libraries that he mentions is Box2D for Processing (formerly PBox2D). Last year he changed the name of the library over but had forgotten to update his book and it's tutorials. I decided to open a pull request that fixed the confusion between PBox2D and Box2D for Processing.