If you want to leverage the whole 100% interoperability of Java (which is a HUGE selling point for Kotlin), I think knowing some Java will be extremely helpful.

If you want to leverage the whole 100% interoperability of Java (which is a HUGE selling point for Kotlin), I think knowing some Java will be extremely helpful. If you're starting a project from scratch, it might not be necessary if you're building on projects like dropwizard-kotlin, etc.