Let's not get wrapped up in the threadlocal. How about this. I have a consuemr

(T) -> Unit

and a producer

() -> T

. I want to store pairs of those, but with a different

T

for each pair.

Put them in individual properties

No, I want a collection.

The elements retrieved from a collection cannot have a different type at compile time so you're going to need a

Collection<MyPair<*>>

yeah, I ended up going with something similar