Abstract Class
Articles by Bala Paranj
Let us consider a Food class and various sub-classes such as Cake, Orange etc. There can be no instance of Food class. It is abstract. We are modeling the real world and abstraction is one way by which we deal with complexity. We can only create instances of the sub-classes Cake, Orange etc. These instances will be named birthDayCake, anniversaryCake etc. The sub-classes are concrete and you can create any number of instances.
OOAD skills for the real world projects
Study Guide - Object Oriented Analysis and Design with UML