Re: How to identify the cause of ClassCastException?

Daniel Pitts <>
Wed, 21 Nov 2007 11:10:40 -0800
www wrote:


I have two classes: State and WarmState.

public class State
    ... //many fields

public class WarmState extends State
    ... //more fields

Now, I have a State reference state, whose corresponding object was
created and filled. I believe/guess/thought it is a WarmState object.
Now I need to pass state to a method which only take WarmState
parameter. So I cast state to WarmState type. But I ran into
ClassCastException. Like I said, state was created and loaded from a xml
file. I hope to find out what caused ClassCastException. But neither of
these gave me a clue:


Thank you for your help.

public class Main {
     static class Foo {}
     static class Bar {}

     public static void main(String[] args) {
         Object o = new Foo();
         Bar bar = (Bar)o;
Exception in thread "main" java.lang.ClassCastException: Main$Foo cannot
be cast to Main$Bar
    at Main.main(
That quite clearly says I'm trying to illegally cast a Foo to a Bar.
What is YOUR exception message say?

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