When I code in Python I always have ipython console handy to try snippets of code and to autocomplete methods and fields.
Contrast with some Java I was doing recently (granted, without a Java IDE) and I found the whole cycle painfully slow. Even things the compiler picked up were a magnitude slower to find than when I was in ipython. And then there were plenty of things the compiler wouldn't get, which could take a good minute for me to discover from the time I made the edit. It's insane to me that people don't work in a REPL.
I find iPython interesting but haven't figured out how to integrate it into my current workflow of Sublime/Terminal.
Sound quality isn't great but hopefully it demonstrates what I'm talking about.
This was your problem. Programming Java without an IDE that recompiles your changes on the fly is just so arcane and really slows you down as you noticed.
Start your program in your IDE's debugger (or point it to your application server where your program is running) and you can change the code immediately, rerun your methods, change variables, inspect the objects, etc.
It's more than a simple REPL, it's a full-blown debugger and it comes really close to what you have in a SmallTalk image where your code, data, and environment is all the same.