Depends what you want. If you want to go into Android development, then I would say that Kotlin is the go to language. Being able to read and write Java is als

Depends what you want. If you want to go into Android development, then I would say that Kotlin is the go to language. Being able to read and write Java is also beneficial imo, since some projects also have old code in Java. However all the teams I've worked in are committed to write their Android applications in Kotlin. I also see that Kotlin gains traction in backend development, since it's fully interoperable with Java.