Nice to have a Java based game. I used to be a java dev. That's definitely a plus for you. I'm sure your theme could have been "Only One Java Dev" :) 
Having said that, there's lots of room for improvement, but you are in the right track. Don't be afraid of testing things out and accumulate experience.

Here's mine if you can spare some time playing it. Many Thanks:
https://itch.io/jam/gmtk-2019/rate/463337

There is a lot you could improve here. I am going to assume this is one of your first times trying this out, and if that's the case, you should look up some tutorials on this kind of game! It's one way to jumpstart your experience so you don't start with nothing.