A superclass variable can reference a subclass object

A reference variable of a superclass can be assigned a reference to any subclass derived from that superclass. In the following program, obj is a reference to NewData object, Since NewData is a subclass of Data, it is permissible to assign obj a reference to the NewData object. When a reference to a subclass object is assigned to a superclass reference variable, you will have access only to those parts of the object defined by the superclass. This is wayobj can’t access data3 and data4 even it refers to a NewData object.

Program

Program Source

class Data {
    
    int data1;
    int data2;
}

class NewData extends Data{
    
    int data3;
    int data4;
}

public class Javaapp {

    public static void main(String[] args) {
        
        Data obj = new NewData();
        obj.data1 = 50;
        obj.data2 = 100;
        System.out.println("obj.data1 = "+obj.data1);
        System.out.println("obj.data2 = "+obj.data2);
    }
}

FacebookGoogle+