Question

In unit 6 we are introduced to the concept of polymorphism which is derived from the Greek words poly, which means many and morpheus, which means form, structure. Discuss polymorphism in objective oriented programming and provide a java example that details the implementation of polymorphism in java objects.

Answer 1

Polymorphism is the building bloc of the Object oriented Programming concepts

Polymorphism is a type of overloading. Parent object reference is used to call the method of child object methods.

We will counter many important instances where we can find the polymorphism helpful.

Polymorphism can also be defined as overloading. Overloading means nothing but the compiler will understand the method to be called based on the type and number of arguments of the method.

So, Overloading is a type of static Polymorphism, because it is judged at Compile time.

Overriding is the type of Dynamic Polymorphism, because it is judged at run time.

I will show an example of different types of Polymorphisms stated above.

For Dynamic Polymorphism - Overriding

Animal.java

public class Animal {

   public void bark() {
       System.out.println("Animals will shout !!");
   }
}

Cat.java

public class Cat extends Animal{
  
   @Override
   public void bark() {
       // TODO Auto-generated method stub
       System.out.println("Cat will say Meaww");
   }

}

Dog.java

public class Dog extends Animal{

   @Override
   public void bark() {
       // TODO Auto-generated method stub
       System.out.println("Dog will say Bow Bow");
   }
  
  
  
  

}

AnimalMain.java

public class AnimalMain {

   public static void main(String[] args) {
       // TODO Auto-generated method stub

      
       Animal a = new Animal();
      
       Cat c = new Cat();
      
       Dog d = new Dog();
      
      
       //Here bark() will be overrided.This is dynamic Polymorphism
       // JVM will decide which bark() needs to called during run time
       System.out.println("Calling bark() method from Animal which is parent refference.");
       a.bark();
       System.out.println("Calling bark() method from Cat which is child refference.");
       c.bark();
       System.out.println("Calling bark() method from Dog which is Child refference.");
       d.bark();
      
       a = c ;
      
      
   }

}

Output

Calling bark() method from Animal which is parent refference.
Animals will shout !!
Calling bark() method from Cat which is child refference.
Cat will say Meaww
Calling bark() method from Dog which is Child refference.
Dog will say Bow Bow

For Static Polymorphism - Overriding

StaticPoly.java

public class StaticPoly {
  
   public static void main(String[] args) {
  
      
       //These both are different methods with same name.
       //But this will be interpreted by the compiler during the compile time itself by matching the argument type and number of arguments.
       //This is called static Polymorphism
       System.out.println("Calling printHI() method without argument");
       printHi();
       System.out.println("Calling printHi(5) method with argument");
       printHi(5);
   }

   private static void printHi(int i) {
       // TODO Auto-generated method stub
      
       for(int j=0;j<i;j++)
       System.out.println("Hi");
      
   }

   private static void printHi() {
       // TODO Auto-generated method stub
       System.out.println("Hi");
   }

}

Output

Calling printHI() method without argument
Hi
Calling printHi(5) method with argument
Hi
Hi
Hi
Hi
Hi

Feel free to ask any doubts, if you face any difficulty in understanding.

Please upvote the answer if you find it helpful