I wasn't very sure of myself and asked him to give me a hint. I remembered that it was something like const, as well as something else. (I have been doing much more C than Java programming lately, and I kind of got the two mixed up.). I'm now pretty sure he was asking about the visibility and extensability of the method types defined in the interface. Which I think is Default visibility, and Final extensability. I am fairly certain I got this answer wrong as well.