[goto11]

> Clearly then, people don't have problems grasping abstract concepts. They just learn the definition and possibly bunch of examples and they're done.

I think the crux is explaining how the abstraction is useful. The Comparable interface doc explains it in the very next sentence: Lists (and arrays) of objects that implement this interface can be sorted automatically by Collections.sort (and Arrays.sort). Every Java programmer can understand this and see its purpose

The difference is that in Java and most other languages abstract mathematical concepts are treated as means to an end, not a goal in itself.