This section covers modifying collection membership.
Changing the membership of a collection (excluding collections of interfaces)
Changing the membership of a collection reference to a superclass of the current collection does not require a reorganization as long as the keys remain valid.
Changing the membership of a collection reference to a subclass of the current membership class requires a reorganization. All instances of the collection must be empty or must refer to an instance of the new membership class or a subclass of that class.
Changing the membership of a collection reference to a completely different membership class requires a reorganization. All instances of the collection must be empty.
Changing the membership of a collection of interfaces
Changing the membership of a collection of interfaces to an interface that is extended by the current interface does not require a reorganization as long as the keys remain valid.
Changing the membership of a collection of interfaces to an interface that extend the current interface requires a reorganization. All instances of the collection must be empty or contain instances that implements the interface or instances that extends that interface.
Changing the membership of a collection of interfaces to a completely different interface requires a reorganization. All instances of the collection must be empty.