Now, about the "else if", I also felt bad about it, and I'm thinking about a changing for it, I'm still working on it, as in a lot of features. If you want to add some feature or change something, please feel free and do it - just show your purpose before do anything, so we might discuss how it will work .
And yes, I started this project while on university, and I don't think it sucks, because my intention is not to create a new technology - at first instance - but help people who want to learn how to write a programming language (as you can read on the README file), whatever comes to this project (bad or good), it will be well accepted for learning.
I also agree with you that Java is not the best tool for implement such thing, and I was thinking about rewriting it to C++ or Python.