doubt in class hierarchy

[Ankitt Dhebarr]

Fellas !! I have a doubt in class Hierarchy!! Please Help me !!

  1.  interface Min{}
       2.
       3.  class A{}
       4. 
       5.  class B extends A implements Min{}
       6.
       7.  class C extends B{}
       8.
       9.  public class CCExp{
     10.      public static void main(String args[]){
     11.           A a=new A();
     12.           B b=new B();
     13.           C c=new C();
     14.           Min m=null;
     15.           b=(C)m;
     16.           m=(Min)b;
     17.           A a2=(A)m;
     18.           B b2=(B)a2;
     19.           Min m2=(C)b2;
     20.           C c2=(C)m2;
     21.      }
     22. }  

Here we are supposed to find at which line an exception is thrown
I think it should be line 14 but thats not the answer. Thats because if it would have been B b=new C(); then we could have written b=(C)m but the line is B b=new B();
This example is taken from Devaka Coorey !!

[Ruben Soto]

The code is correct.

B b=new B();
Min m=null;
b=(C)m; // 1

At line // 1: b is a reference of type B, and you are trying to assign it a reference of type C (which points to null.) Since C is a subtype of B, this will not be a problem.