Use of instanceof in java

Question

can any one tell me the use of instanceof keyword in java
.and how it is used.
and were it is used
reply me
regerd
saravana

Answer 1

Okay, understood.
However, I'm receiving a ClassCastException "unexpectedly".
Definitions:
public interface MyInterface { // definition }
public class MyAbstractSuperClass implements MyInterface { // definition }
public class MySubClass extends MyAbstractSuperClass { // definition }
public class ProvidingClass {
       * Returns instance of MyInterface.
      public MyInterface getMyInterfaceObj(Class className) {
            return myInterfaceObj;
}This code ...
Code A:
MySubClass mySubClassObj = (MySubClass)ProvidingClass.getMyInterfaceObj(MySubClass.class);... throws a ClassCastException.
Consider the following code based on the same definitions above.
Code B:
MyInterface myInterfaceObj = ProvidingClass.getMyInterfaceObj(MySubClass.class);
if (myInterfaceObj instanceof MySubClass) {
      // Do stuff
else {
      System.out.println("Found class:  " + myInterfaceObj.getClass().getCanonicalName());
Result:
... I get the following:
"Found class: fully.qualified.package.name.MySubClass"
Question:
Why do I receive a ClassCastException in Code A when the class that is returned in Code B indicates (through getCanonicalName() ) that it is of the type that I am trying to cast it to?
What would cause such an exception?
Thank you for your help!
- KFM
Edited by: jackstr66 on Nov 1, 2007 12:09 PM
Edited by: jackstr66 on Nov 1, 2007 12:10 PM