Polymorphism

In computer science, polymorphism refers to the ability of a programming language to interpret objects in different ways based on their class or data type. In essence, it is the ability of a single method to be applied to derived classes and achieve a proper output.

Three branches of polymorphism

• Ad hoc polymorphism is when a function is implemented differently depending on a limited number of specified types and combinations of input parameters. An example of ad hoc polymorphism is function overloading.
• Parametric polymorphism is when code is written without any specification of type, and so can be used with any number of different types specified later. In object-oriented programming, this is often called generic programming.
• Inclusion polymorphism, also known as subtyping, is when a single name refers to many instances of different classes as long as they share the same superclass.

Polymorphism example in Java

Example code

class OverloadedObject 
{
  void overloadedMethod (int a) 
  {
    System.out.println("This method is called when the parameter is an 
integer. a = " + a);
  }
  void overloadedMethod (int a, int b) 
  {
    System.out.println("This method is called when there are two 
parameters, and they are both integers. a = " + a + ", b = " + b);
  }
  void overloadedMethod (double a)
  {
    System.out.println("This method is called when there is one 
parameter, and it is a double-precision number. a = " + a);
  }
}
class DemonstrateOverloading
{
  public static void main (String args [])
  {
    OverloadedObject myObj = new OverloadedObject(); 
    myObj.overloadedMethod(1);
    myObj.overloadedMethod(2, 3);
    myObj.overloadedMethod(4);
  }
}

Example code output

This method is called when the parameter is an integer. a = 1
This method is called when there are two parameters, and they 
are both integers. a = 2, b = 3
This method is called when the parameter is a double-precision number. a = 4

Notice that it produces different output based on different input parameters, even though the class and method name invoked are the same each time.

Object-oriented, Output, Parameter, Polymorphic virus, Programming language, Programming terms