ClassCastException Exception

[Smita Chopra]

The following program gives a ClassCastException at runtime

 public class Test {
   public static void main(String []args) {
     
      String s = new String();
      Object obj = new Object();
      
      s = (String)obj;
   }
}
 

Can you please tell me why doesn't it give an error at compile time when its very clear that assigning Object to String is going to fail.

[Steve Morrow]

It may be clear to you, but the compiler doesn't have any way of knowing for certain that such a cast won't work. The example posted is trivial; quite often, a particular implementation is unknown at compile-time, so the compiler trusts you know what you're doing when you cast a reference.

[Anil Chandran]

Only at runtime it can be made sure that the object cant be casted to a string .

Object is a super class of String . So casting an object to string cant cause a compile time error.