ClassCastException occurs, when you try to assign a reference variable of a class to an incompatible reference variable of another class.

Example

import java.util.Vector;

public class CastException {

  public static void main(String[] args) {
  Vector v = new Vector();
  int i = 10;
  Object obj = v.add(i);
  try {
  String y = (String)obj;
  v.add(y);
 } catch (ClassCastException e) {
  System.out.println("Class is really: " + obj.getClass().getName());
  e.printStackTrace();
  }
  }
}