Eclipse also shows You how to repair suchproblem. Open Your DuplicateKeyException class. In the left editor column, before line numbering, You will see yellow bulb with warning symbol. Click on it and Eclipse offer You how it can be repaired.
If You're not interested to see warnings about this kind of problems, it is possible to turn this mechanism off:
1. from menu choose Window -> Preferences
2. in preferences window, in left tree choose Java -> Compiler -> Errors/Warnings
3. on the right side choose PotentialProgrammingProblems -> Serializable class without serialVersionUID and change Warning to Ignore
[ November 05, 2005: Message edited by: KArol Muszynski ]