The example with Airport and Arcade is strange for an example of inheritance/bad inheritance. The two are not related in this way, in OO parlance, an Airport is not an Arcade, we usually say 'an Airport _has an_ Arcade'. (Contains an object of type 'Arcade')

Otherwise, I agree that interfaces are 'a good thing', I think the Java way of doing things is good. There you can create functions which take any object which implements a certain interface, and its simple to make a class to extend an interface.

But I digress, I will go see what your class does now :)
C.