Thanks for the suggestion. My qusetion was related to serializable (or similar) interface that does not have any method of it's own. I have BaseClass inplementing Serializable and SubClass extending BaseClass. So how do I make sure that SubClass really is serializable.
Serializable is a 'tag' interface; it doesn't contain any methods, it is just used to indicate to the system that this class should be Serializable. However it behaves in exactly the same way as other interfaces, so your subclass will indeed be Serializable if the base class is.