I think it really depends on your goals. What are trying to accomplish/learn by using Java? What about a 2D engine? 2D engines are great for prototyping and making simple things quickly. If you are experimenting with game design, they can save a lot of time. But what you don't learn is what is really going on under the hood. If you want to get better at programming, then using something lower level will teach you the problem solving skills you need.

Are you making Java Applet games so they can be on the web for others to play? Applets are not the way to go. You either want something like Unity - https://unity3d.com/ or something more low level - Phaser IO - http://phaser.io/

If you really like Java, you can use libGDX - https://libgdx.badlogicgames.com/.

Or, if you really want to learn what is going on, checkout my Github code for the book "Fundamental 2D game programming with Java".

https://github.com/TimothyWrightSoftware/Fundamental-2D-Game-Programming-With-Java

Even if you don't buy the book (which is really expensive, sorry) the code examples are a great starting place for some "From Scratch" gamedev.