why displaying parent objects by child class object only giving default values !!?

Question

class one

{

int age;

String name;

}

class two extends one{

void display()

{

System.out.println(age+name);

}

}

class extenddoubt

{

public static void main(String args[])

{

one o=new one();

o.age=4;

o.name="john";

two t=new two();

t.display();

}

}

this code is not returning 4, john but 0 and null :((

Answer 1

In your main method, you are declaring 2 distinct objects - o as an object of type one, and t as an object of type two.

After you create object o, you set its class variables age and name to 4 and "john" respectively, but do not set object t's values.

When you create object t, this creates a new object of type two. While it does inherit the interface of object one, it does not receive any values from when you set them on object o. As a result, your age defaults to 0 and name defaults to null, resulting in the output you are seeing.

To get a different output, you would need to set the variables on object t:

t.age = 4;

t.name = "john";

or create object t from object o:

two t = o;