Re: Android & Java
I'm not projecting my prejudices. I base my comments on my own experiences.
Almost every Android developer uses at least a little bit of Java. You really have no choice in the matter. Java is the defacto language for Android.
But... you put a bunch of Android developers in a room, and I'll bet each and every one of them will put their hands up when asked whether they use Java, despite the fact that a large number of them problem only know the bare minimum required to get their app integrated. I'd probably put my hand up, because I do actually know Java and have used it in the past. Do I use it today for our Android apps? Not really. I step in and out of it in the debugger from time to time, but that's about it.
So on that basis, yes, Java is the most used language, because you have no choice.
My point was, however, that the vast majority of developers use the absolute minimum, and probably quite a lot of those only use the boilerplate wrappers that their platform of choice generates for them.
We have a UI layer written in Java for our Android apps, the same way we have a Swift layer for our iOS, macOS, and tvOS apps. But they really are very thin layers around our cross platform C++ engine. We'd have been crazy to choose Java as our main development language. As it happens we do call into some non-UI Java libraries on Android today (MediaDecoder, et al.), but we'll be switching those out and calling the C based OpenML AL APIs that Android exposes directly at some point in the future. Basically to get rid of the Java overhead.
With that all said, you might be right. Java could well be the most popular language for Android development. But I honestly doubt it. In 2015 Unity was claiming they had 4.5 million registered developers. (And last year they had 5 billion "Made with Unity" downloads in Q3 alone.) Xamarin has 1.4m active developers as of April this year. Unreal has over 2 million. These aren't small numbers. Especially when you consider some estimates put the total number of Android developers at only around 6 million in total.
Oh, and no C++ game engine uses Java for its UI. ;)