IMO its just like with every other feature. When a...

# language-proposals

[Andreas Sinz]

IMO its just like with every other feature. When a java dev starts writing Kotlin, he writes java-ish Kotlin code. After some time he finds out about the cool new feature (e.g. Sealed classes) and then starts to incorporate it into his codebase. A new java dev doesn't need to use partials/sealed classes/delegation from the get go