Polymorphism without Inheritance

October 6, 2010

Can Polymorphism exist without Inheritance?

Abstraction“, “Encapsulation“, “Inheritance” and “Polymorphism” forms the basic building blocks of OOA&D.
We are so much overwhelmed by these facts that an immediate answer is “No“.

In Java there are two types of Polymorphism. One is Runtime(Dynamic) and other is compile time(Static).
In Runtime polymorphism the actual method to be invoked is decided based upon the actual object that the reference type refers at Runtime. This is achieved by OVERRIDING the method in sub classes. Of course this is where “Inheritance” is the KEY which is used to implement “Polymorphism”.

In Compile time or Static polymorphism, the method to be invoked is decided at compile time by diagnosing parameters of the method. This is implemented using Method OVERLOADING. Now this one does not depend on the Inheritance hierarchy because a method can be overloaded in different ways in the same class.

What does this mean?
Even without the Inheritance hierarchy we can have Polymorphism though of a Static kind.