I've found that migrating all your trunk code (data and infrastructure classes) to kotlin is the biggest win, and you can leave your old leafs (fragments and vi

I've found that migrating all your trunk code (data and infrastructure classes) to kotlin is the biggest win, and you can leave your old leafs (fragments and view models) in java if you want do a low risk migration. If a view isn't broken, you don't need to fix it, but getting nullability annotations in your data models and REST commands is a huge win for newer views and business logic going forward.