I mean mixed codes. My team leader does not agree with me for writing mixed Java and Kotlin. He wants only Java or Kotlin.

you should get rid of such team lead

Agree… The answer should be: “We don’t have Java and/or Kotlin…we have JVM code ;)”

If you already have a large code base in Java you cannot convert everything to Kotlin overnight but luckily both Kotlin and Java can coexist in the same project so it makes the transition easy

I would agree with such a team lead as it doesn’t enhance code readability to mix languages. In my opinion, you should at least have a good separation between them, let’s say in different gradle modules or packages.