I'm putting the music app on the back burner for now and am going to concentrate on an idea I've got for a 2D game. So, I'm hitting the libgdx forums on BadLogic again and diving into how it's implementation of Box2D works (as well as the fundamentals of Box2D itself.) Spent a good chunk of time yesterday doing that.
On Friday I received a book from my dad entitled "Secret Codes and Cryptograms" which has over 600 codes to crack. Rather than dive directly into that, I decided to start writing a Java program for doing cryptographic analysis and decryption. Since my knowledge of the Swing GUI is nil and I wanted a nice GUI to help me in my code-breaking attempts, I started looking into that.
I'm using the Eclipse IDE and found the WindowBuilder Pro plug-in. WindowBuilder Pro is a Visual Editor for GUIs. A couple of tutorials later I'm up to speed on that and am currently design my UI for decryption. The idea is to give it the following capabilities: text entry, letter frequency analysis, 'guessing' based on letter frequency, mono-alphabetic substitution and (maybe) brute force methods. We'll see how it goes.