Runtime Polymorphism in Java-3

Runtime Polymorphism in Java-3

Runtime Polymorphism with data member


Method is overridden not the datamembers, so runtime polymorphism can't be achieved by data members.
In the example given below, both the classes have a datamember speedlimit, we are accessing the
datamember by the reference variable of Parent class which refers to the subclass object.
Since we are accessing the datamember which is not overridden, hence it will access the datamember
of Parent class always.


Rule: Runtime polymorphism can't be achieved by data members.

    class Bike{ 
     int speedlimit=90; 
    } 
    class Honda extends Bike{ 
     int speedlimit=150; 
     
     public static void main(String args[]){ 
      Bike obj=new Honda(); 
      System.out.println(obj.speedlimit);//90 
    } 

Output:90

Runtime Polymorphism with Multilevel Inheritance

Let's see the simple example of Runtime Polymorphism with multilevel inheritance.

    class Animal{ 
    void eat(){System.out.println("eating");} 
    } 
     
    class Dog extends Animal{ 
    void eat(){System.out.println("eating fruits");} 
    } 
     
    class BabyDog extends Dog{ 
    void eat(){System.out.println("drinking milk");} 
     
    public static void main(String args[]){ 
    Animal a1,a2,a3; 
    a1=new Animal(); 
    a2=new Dog(); 
    a3=new BabyDog(); 
     
    a1.eat(); 
    a2.eat(); 
    a3.eat(); 
    } 
    } 

Output: eating
        eating fruits
        drinking Milk

Try for Output

    class Animal{ 
    void eat(){System.out.println("animal is eating...");} 
    } 
     
    class Dog extends Animal{ 
    void eat(){System.out.println("dog is eating...");} 
    } 
     
    class BabyDog extends Dog{ 
    public static void main(String args[]){ 
    Animal a=new BabyDog(); 
    a.eat(); 
    }} 

Output: Dog is eating

Since, BabyDog is not overriding the eat() method, so eat() method of Dog class is invoked.