You can mix Kotlin and Java in the same project easily. I have a project where we have a bit of both. All the new code is written in Kotlin and some older features are converted to Kotlin when we feel like it.
Re:Android now supports Kotlin
by monkmartinez on Wednesday May 17, 2017 @03:30PM
(#14361999)
I kind of gave up on Java and Android a few years ago and picked up Python. I have given Go a whirl... but it doesn't tick all the boxes for me. I really, really want to build apps for all the platforms with one language and awesome GUI's.
I'll keep writing Java to build Android apps though. I'm sure it's "more fun" or whatever, but Java's worked just fine for me thus far. I'm used to the verbosity, and have no desire to start from scratch with another language. If some huge benefits were presented, I would. But, I'm failing to see any.