In this lecture we are discussing:

#1 method overriding

#2 Necessary condition for method overriding

What is method Overriding?

It is way to override the parent class method in child class .

class Parent{

int a;

public void show{System.out.println(“this is parent”);}

}

class Child extends Parents{

    int a=10; //override a

    public void show(){System.out.println(“this is child method”);} //method override by child class

}

class Main{

    public static void main(String []args){

        Child c=new Child();

        c.show(); //call the child class override method

           }  

}

 — method overriding is run time polymorphism

 — it is use to increase the reusability of code

#2

for a method to be overridden, the following conditions must be met:

 — The method in the subclass must have the same signature (name, number and type of parameters) as the method in the superclass.

 — The method in the subclass must have the same return type (or a subtype) as the method in the superclass.

 — The method in the subclass must have the same access level (public, protected, or private) as the method in the superclass.

 — The method in the subclass must not be static, while the method in the superclass must be marked as non-final.

 — The overridden method must be visible from the subclass it means you can change access modifiers but there is condition for

    — you need to increase visibility but you cannot reduced it , you can do it using access modifiers.

    — you can change access modifiers in this manner

       private -default -protected -public (in upcoming lecture access modifiers has been discussed)

for knowing about access modifiers wait for access modifiers lecture in this playlist

class A{

     void show(){ // — by default access modifier is default

        System.out.println(“A”);

    }

    int a=5;

}

class B extends A{

     protected void show(){ //– access modifier is protected –we can increase visibilty

        System.out.println(“B”);

     }

}