Re: How to identify the cause of ClassCastException?

From:
Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 21 Nov 2007 11:10:40 -0800
Message-ID:
<KNSdnXFiHuQvH9nanZ2dnUVZ_qainZ2d@wavecable.com>
www wrote:

Hi,

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:

e.getMessage()
e.getLocalMessage()
e.printStackTrace()

Thank you for your help.

<sscce>
public class Main {
     static class Foo {}
     static class Bar {}

     public static void main(String[] args) {
         Object o = new Foo();
         Bar bar = (Bar)o;
     }
}
</sscce>
<output>
Exception in thread "main" java.lang.ClassCastException: Main$Foo cannot
be cast to Main$Bar
    at Main.main(Main.java:7)
</output>
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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