Question

If a class A implements interface I1 and class C and D are derived from class A, a variable of type I1 can be used to hold references of what type of objects? which one is correct

1. A, C, and D

2. A and D

Answer 1

Ans)

• Objects refrance of Class A,C and D can be stored in the variable type of interface I1.  
• Because refrance of interface I1 is first points to subclass,first it will check the subclass if the method is not avilable in sublass then it will find that method in its super(Parent) class
• For better understanding i am sharing the code,you can refer thaat code for ur understanding

I1.java

public interface I1 {
   int ref=0;
   public void reef();

}
////

A.java

public class A implements I1{
   int ref=0;

   public void reef()
   {
       System.out.println("in class A");
   }
}

///

c.java

public class C extends A {
   public void reef()
   {
       System.out.println("in class C");
   }

}

//

D.java

public class D extends A {

  

}

///

Test.java

public class test {
public static void main(String[] args) {
  
   I1 d=new D();
   d.reef();
  

   I1 c=new C();
   c.reef();
   I1 a=new A();
   a.reef();
          
  
}
}
///

In the above code you can see that there is no method in class D ,hence the refrance pointer of Interface I1 will check in Class A to print method D

Screenshot of the result in console is shown below:

Thank You!