Most of the changes for me from 10/20+ hours to now we're more about identifying a style that works as effectively as I can. These types of behaviours are normal in all but the most idiomatic languages, so if anyone is doing java dev as their daily language, Kotlin felt very natural(though you really are limited to Intellij since the IDE does a ton of lifting to make your life easy).
Kotlin is probably more similar to Java than any other mainstream language. There’s almost no learning curve there, while going from Java to other “easy” languages like Python requires significantly more time to get used to.
You can do the first one basically the same way you'd do kotlin, the second one can get pretty hairy if someone decided to bring in a bunch of macro heavy DSLs and syntax extensions.