I am struggling to port some older code from a jvm-only project to combined jvm/js. One of my classes was extending java.util.HashMap, which is now impossible, of course, as the kotlin HashMap is a final class. Seems I have two options: 1) implement Map and add

entries()

,

keys()

,

size()

,

containsKey()

etc or 2) remove class inheritance and reduce the map to a backing field. Or did I miss something? (Hoping so. Would like to change as little as possible.)

Maybe a class delegation, depends what you want to do

Maybe you could use delegation for this and delegate all calls to MutableMap, so it would be multiplatform solution

I'm not using delegation, although that wouldn't be all that different. I'll pick up this thread again if I choose to use delegation!