Personally as a JVM dev, I see no reason to choose kotlin over Java unless I'm stuck in an environment thats running a JVM < 8.

For years people have been using stuff like Lombok as a half-baked Java dialect with more usable defaults: non-nullable types, immutable objects with getters and builders with named setters, sneaky throws, meaningful #equals and #toString. Kotlin just concisely supports what we’re already doing. And for everyone who’s been waiting for Java fibers, well, Kotlin coroutines are out of beta.

I do like Scala, I wish we worked in an industry that could expect everyone to master it, but it’s probably too much to ask.