Sunday, September 16, 2001 10:08 PM
Interfaces and abstract classes do not need to implement Serializable, however if they do then you guarantee that any sub-classes will also be serializable. Otherwise, the person who implements your interface or extends your class may choose not to implement Serializable at the same time. Also, any data in the abstract class will not be serialized unless that class implements Serializable.
You mention .ppm files which I think are a type of image, correct? You should be aware then that the Image class is not serializable. If you must save an image to a stream, then you will need to handle it specially. Check out this FAQ entry for more details.