Under certain circumstances, when Java objects use serialization to
store objects, the version of the class reading the data could be
different from the version of class that wrote that data.
This example demonstrates some of the compatible changes that
Serialization handles without using class-specific methods.
As with all examples that deal with evolution, the evolved class (AClass)
must define a serialVersionUID field that is obtained using
the command serialver on the original class (AClass).