subclass : Java Glossary


subclass
You create a new Dalmatian subclass by deriving it from (i.e. extending) a base/superclass Dog. Even though the subclass Dalmatian typically has more methods in it than the original Dog base/super class, we still call Dalmatian a subclass of Dog.

This is the reverse of the way a mathematician might look at it. From the point of view of mathematical set theory, Dalmatian has a superset of the methods of Dog.

I’d prefer to call them the less ambiguous base and extended / derived class, rather than super and sub class. To help you remember, "Mom makes super pie" — the mother original class is the superclass.

Another way to remember it is that the set of all Dalmatian objects is a subset (subclass) of the set of all Dog objects.

Yet another way to help you remember is the super keyword as in:

super.somemethod();
lets you access Mom’s version of the method, so Mom, the class you were derived from, is the superclass.

Yet another way to help you remember is to think of a class tree dangling down from Object at the top. The superclass is above, the subclass below.


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