You can also use Scala: https://github.com/pkukielka/stronghold-defense

The main problem which you will get with languages like Scala , Clojure and other functional languages on JVM is a lot of garbage generated during the execution. And garbage collector on Android isn't even remotely as effective as standard one. This often forces you to write code which is not really idiomatic and which rather resembles java. That is possible in Scala (I'm not sure about Clojure), but to some extend it defeats whole purpose of using something other than java.

Disclaimer: I'm the author of linked game.

You can use any of the JVM languages with libgdx, such as Clojure, Scala, Kotlin even JRuby [1]

[1] https://github.com/mickey/libgdx-jruby-exemple

I've often considered C++ as a mandatory requirement for game development. Java is fine though, but I just don't use it, and if I have to choose between java and C++, I go for C++...

I've often considered Assembler as a mandatory requirement for game development. C++ is fine though, but I just don't use it, and if I have to choose between C++ and Assembler, I go for Assembler...

What a difference two decades makes eh?

It really depends on what you're doing. Triple-A games and most graphically advanced 3D games pretty much require you to use C++.

And assembly. I've heard from my boss (who did games a while ago at a very notable company that still makes very well-known Triple-A games) that when they were making a sequel to their first game, getting an assembly programmer who really knew the CPU pipeline increased the performance of their graphics pipeline by 40-50%. (at least) I would imagine that modern games continue to need people who can program extremely optimized assembly, especially for consoles.

If you prefer C++, Cocos2d-X may be a good fit for you. I've tried it, but I just couldn't stand it, because of the way they've translated the Objective-C object model and bolted this on top of C++. To me it looks hardly idiomatic C++. I can understand their technical reasons though (easier to translate the original Cocos2d-iphone to C++).

While I understand the desire for good performance, using a higher-level language can give you some huge gains in the prototyping and iteration phase of design. That's where it counts when it comes to trying out game ideas and seeing what works.

There is actually a great deal of C++ in libGDX.