CODEWITHSUNDEEP
javavariablesinheritanceinstance
Siddappa Walake
Siddappa Walake

Reputation: 323

Inheritance with a variable in java

Can anyone clarify me. Here instance method is overridden but variable is not. output is: B 10 

class A{
    int i=10;
    public void name(){   
        System.out.println("A");
    }
}

class B extends A{
    int i=20;
    public void name(){        
        System.out.println("B");
    }  
}  

public class HelloWorld { 
    public static void main(String[] args){       
        A a = new B();
        a.name();
        System.out.println(a.i);
    }
}

Upvotes: 3

Views: 116

Answers (3)

Mohit Tyagi
Mohit Tyagi

Reputation: 2876

In Java instance variables cannot be overridden, only methods can be overridden. When we declare a field with same name as declared in super class then this new field hides the existing field. See this Java doc Hiding Fields.

Upvotes: 1

Al-un
Al-un

Reputation: 3412

You cannot override attribute, you can only override method:

public class A{
    private int i=10;

    public void name(){   
        System.out.println("A");
    }

    public int getI(){
        return i;
    }
}

public class B extends A{
    private int i=20;

    public void name(){        
        System.out.println("B");
    }

    @Override
    public int getI(){
        return i;
    }
}  

public class HelloWorld { 

    public static void main(String[] args){
        A a = new B();
        a.name();
        System.out.println(a.getI());
    }

}

In your example, you define variable a as type A so the i value in B is ignored.

Upvotes: 1

Bathsheba
Bathsheba

Reputation: 234665

You are absolutely correct. Methods are overridden in Java if the parameter list and function names are identical, and the return types are covariant.

i in the base class is simply shadowed: a.i refers to the i member in the base class, since the type of the reference a is an A, even though it refers to a B instance.

Upvotes: 4

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