Even Kotlin has taken over Java as the most used language for android development. Kotlin is basically just a different syntax on top of Java, but it is significantly nicer and handles some stupid decisions of Java like Null’s in a far far more sane way. I can whole heartedly say to use Kotlin over Java, they both work in the same places, never a reason not to choose Kotlin.
Scala I like even more, but it’s more… dense than Kotlin, and comes with extra standard library stuff. ^.^;