I vote -1 to folding the SerializationContext and DeserializationContext interfaces into their implementation classes since these interfaces seem to be part of the interface to the encoding subsystem.
Building subsystem interfaces using java interfaces rather than java classes helps to reduce the coupling between subsystems. For instance, a class which implements a subsystem interface may have a method which is of no concern to other subsystems. If the subsystem spans more than one java package, the method needs to be public. Then having a separate interface means that the method need not be exposed to other subsystems. (Granted, if the subsystem equates to a java package, you can use package scope to achieve the same ends, but package scope isn't obvious due to the lack of a keyword to denote it and packages are not ideal for constructing subsystems since they don't nest.) Glyn
