OCPJP(SCJP 1.6) Question 29

   1: public class StringInstanceOfTest {

   2:     public static void main(String[] args) {

   3:         String s = null;

   4:         if(s instanceof String){

   5:             System.out.println("s is instance of String");

   6:         }

   7:         else{

   8:             System.out.println("s is not an instance of String");

   9:         }

  10:     }

  11: }

Output :

A. Compilation fails.

B. Throws Exception at line 4.

C. Prints “s is instance of String”.

D. Prints “s is not an instance of String”.

Answer : D

There is no problem with the syntax of the code so there is option A is incorrect. The code compiles perfectly. Instanceof operator does not throw any exception so B is incorrect. The answer is either C or D.

The instanceof operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface.

When using the instanceof operator, keep in mind that null is not an instance of anything.

So from the above explanation option D is correct .