Hello pickle chips, and welcome to the forums.
I'm glad you like our game.
Getting involved in an open-source project is one of the best ways to progress in programming.
While your idea of displaying the equipment on the character is in itself good (and has been asked and discussed many times), it is by no means an easy one to implement. You would need to get involved in the graphics rendering layer of AT (not the easiest part), and worse, to rpoduce a lot of artwork: the item icons are all differently oriented, and cannot simply be scaled and placed over the hand of the character. It could be simplified by using the same icon for a whole category. IMHO, that's way beyond the scope of a programming beginner.
As you noted, it is programmed in Java, but not the "original" one. This is the Android SDK. It uses the same syntax and base classes as "standard" Java, but with completely different built-in APIs. It involves a lot of XML. Nothing to be afraid of though.
One last note: I've had flamed discussions on this matter with Oskar, but IHMO, AT's code is not the best example to follow in terms of software architecture. While all the functions and algorithms are well-written, I think the way the code is laid out is at best "strange" for a Java program, misapplying (or simply not using) the usual design patterns that make code easier to maintain.
Reading the code, and understanding how it works is a great exercise though.
Don't hesitate to follow
the contribution guide in order to learn how to set up your computer and get ready to dive in the code !