I had a go at making and interpreter for a basic language called Barebones. There are only 4 commands: 3 to interact with integer variables and 1 which is a specific while loop.
If I had my time again I would have followed a more OOP approach and combined my multiple arraylists into a command object and a varibale object. I also would have the different parts of my code into multiple methods so that it would be easier to read. I also need to improve my style with blankspaces. I think I can install a plugin to help. And of course I need to comment more, however, there was a bit of a time limit.