I've definitely copy/pasted a stripe-locked concurrent map a couple times to use it for different types. Basically any re-usable container class is the canonic

I've definitely copy/pasted a stripe-locked concurrent map a couple times to use it for different types. Basically any re-usable container class is the canonical case for generics. I agree that in most other cases, it turns out you can write a simpler API than Thing<OtherThing<Key, ? extends Value>>, and nobody wants to open the door to that mess. But for containers, they either need to dramatically multiply the number of built-in container classes (slice[] map[] are generic in a way), or create a way to write your own.