casting problem

[payal sharma]

class Base extends Object implements Runnable {
 public void run() {}
}
class Child extends Base implements Cloneable {}

class Test {
 Object obj;
 boolean bool;
  static Base b = new Base();
  static Child c = new Child();
  Runnable r1;
  Cloneable c1;
  Cloneable c2;
 Test() {
   super();
 }
 Test(Object x) {
   
  try {
    if ( bool = x instanceof Object ) 
       System.out.println(bool);
  }
  catch(Exception e) {
       System.out.println("Exception 1 caught");    
  }
   
  try { 
    Runnable r1 = (Runnable)x;
  }
  catch(Exception e) {
       System.out.println("Exception 2 caught");     
  }
  try {
     Cloneable c1=(Cloneable)x;    
  }
  catch(Exception e) {
       System.out.println(e);    
  }
  try {
     Cloneable c2=(Cloneable)x;    
  }
  catch(Exception e) {
       System.out.println(e);    
  }
}
 public static void main(String [] args) {
    Test t = new Test(b);
    Test t1 = new Test(c);
 }
}

C:\JAVA>java Test
true
java.lang.ClassCastException: Base
java.lang.ClassCastException: Base
true
Here I am unable to understand the output the class cast exception with
Base two times and then true why?
Please explain this.
thanks in advance
payal
[This message has been edited by payal sharma (edited July 27, 2001).]

[Mikael Jonasson]

The two exceptions for base are:
Cloneable c1=(Cloneable)x;
Cloneable c2=(Cloneable)x;
When called with base. Since all objects extends Object, Test will always print "true" when called with an object (both base and child are objects). Since base implements runnable and child extends base, the cast to runnable will work for both. Child implenets colneable, so the above cast will work for it.
Dow this explain it?
/Mike

[Desai Sandeep]

Payal,
The Base class doesnot implement Cloneable.Hence you cannot cast its instance to Cloneable.You get the two exceptions for statements :

Cloneable c1=(Cloneable)x;
Cloneable c2=(Cloneable)x;

when x is an instance of Base class.
When x is a instance of Child class, the above statements would not give ClassCastException , since Child class implements Cloneable.
When either of the constructors are invoked, each being an instanceof the Object prints true in the output.
Hope this helps,
Sandeep
SCJP2, OCSD(Oracle JDeveloper), OCED(Oracle Internet Platform)