Kotlin is the wave of the future. I still use Java, but I'm transitioning into using Kotlin for backend services. The devs are my work have been moving the app codebase to Kotlin for a couple of years (over a million lines) and it's pretty nice. You reduce a lot of boilerplate and the code can be a bit more dense.

It's perfectly fine to continue to write Android apps in Java, doing that will continue to be supported for all foreseeable future and I do it myself for a hobby app that I maintain.

That said, there are good reasons for the increasing popularity of Kotlin, it's certainly a good language that has noticeable advantages over Java.

Just go ahead with the tutorial. Kotlin is basically identical to Java with only tiny changes, and you can just look those up whenever you see something new.

I did a bootcamp for Java, and lucked into a junior Android dev role, and man, I've really grown to love Kotlin. It really does have all the things I liked about Java, like type safety, but it's so much more concise. It was pretty confusing at first, a lot of Kotlin is just syntactic sugar, and you kinda need to know what Kotlin is cutting out to make sense of things. But once I got into it, it just feels so much faster and expressive than Java.

I'm really happy when I see Kotlin being adopted outside of Android, like in backend services and such. But that rarely happens.

Even for someone who doesn't program in java or Kotlin, I can trod my way through modifying things written in Kotlin where I'm hopelessly lost in Java.

I hate that there is no tooling for kotlin outside of intellij. Decided to learn c as my first language instead. That being said kotlin is Great if you don't mind intellij

What about the Dart with Flutter?