Make a class implement Serilaizable interface dynamically?

I have many classes (50+) in a jar file without source code.I want to make them all implement java.io.Serializable interface so they could be saved to memcached. I guess if java reflection or dynamic proxy can do it for me,that is to say , I dynamically load these classes , and then ,I dynamically make them implement java.io.Serializable interface .Any one could give me some suggestions?