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SCJP Module-6 Question-12

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The program given below will test your understanding of Inheritance in Java and it will also test typecasting of objects from one class to another class.

Given below the sample code :

1 interface zoo {}
2 class A implements zoo {}
3 class B extends A{}
4 class D extends B{
5 public static void main( String[] args ) {
6 B x = new B();
7 // what code should be here
8 }
9 }

What code should be inserted at line 7 to throw " java.lang.ClassCastException " implicitly ?

1. A a = x;
2. zoo z = (D)x;
3. zoo z = (A)x;
4. B b = (B)(Alpha)x;

Answer :

(2)

Explanation :

B(super class of D)cannot be cast to D(subclass of B).

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