If instances of a class exist, JADE prevents the following actions from being performed.
Changing the type of a collection; for example, from an array to a set.
Changing the type of the keys of an
Changing the membership of a collection to completely different types. You can change membership to a subclass but changing to a superclass is dependent on the existing instances.
Moving instances from one database file to another; that is, changing the class map.
For details about using JCF commands to remap classes and move class instances, see "Using JCF Commands to Remap Classes and Move Class Instances", earlier in this chapter.