Hi, I've just bought the book and when it arrives at home I'll begin to read it and having fun.
I know all the programming part can be written in any language, but as the simulator, emulator, ... provided in the book are written in Java I don't know if would be better to write all the code in Java too.
Another question for all you who have followed the project, I'd like to know which programming have you chosen.
I've chosen to write the programming parts in Python, mostly because I wanted to get more practice in writing Python but I am finding it well suited to implementing the API's. I don't think there would be a great advantage to using Java unless you are already comfortable using the language or you want to more experience in it.
I used Java, and it worked well. That being said, I think the language you're most comfortable with is the right choice. None of the programming tasks require highly specialized or sophisticated language features.