Extend an own Exception with an error code

I searched the web but I don't find someone who had the same idea. So maybe it's a stupid idea?

In my program I get data and validate it. If the data is invalid I throw an exception. Somewhere I catch that exception.

Now I want inform the user why the data is invalid. Not with the error message but also with an error code. But how...?

So I had the idea to expand my MyException class.
When I catch that exception I can use getErrorCode to acces it.
But I'm suprised that I never see that before. Is that a bad solution? Is something like that frowned upon?
[ August 08, 2008: Message edited by: Oliver Brocker ]

No. That's a perfectly reasonable thing to do.

Thats a good idea, many use it.

Also, I use to keep enum values inside my exception and when passing arguments to the exception construction I pass a value which is one of the enum value.
If you are on this issue I have couple of more improvements: use the enum value as a key for a message bundle message to your log or even show it to the user.
Further more, if the exception translated to an error shown to the user on the presentation level and you want to be able to trace it back to your logs, you can generate a numeric id and tell the user something like:
"If you wish to contact our support-> this is the error number you received".
The other part here, is that you need to log this down or write the error details in the database so they can be used later on by the support.
This is useful in login/password flows.

Cheers.

Thank you both for your fast replies

And a special to Yuval Goldstein for the further hints

. I will think about it.

java.text.ParseException does a very very similar thing with its error offset.