[brabel]

I've been using Kotlin since 1.0 but I have to say the ergonomics of it are not vastly superior to Java.

As others have mentioned, with Kotlin you're pretty much limited to Jetbrains' IDE, you have a new runtime dependency, not just a compiler, which is rapidly changing and requires updates on the code base frequenly (one of my projects used Kotlin for testing with KotlinTest - which recently changed names to KTest I think - and it was horrible to have to re-write most of my hundreds of tests to be able to upgrade when they went from JUnit 4 to 5 and in the process re-wrote all of it, basically), the compiler is slower and it starts to feel very much once you have thousands of lines of code... not to mention that there's a fairly big overhead of not only having to have javac installed, but also the Kotlin compiler and standard library... also, you probably want to use Gradle with the Kotlin DSL which in my view is really, really slow and unpleasant to work with - though they've finally been improving this recently - in the last couple of years.

So, yeah, I like to write Kotlin code better than Java, but due to all of these factors and the fact that Java is now fairly close to Kotlin in functionality, if I had to start a big project today, I would pick Java for sure.