Adds an object to the list.
Parameters: o - the object (must be an instance of the Group class). throws: java.lang.UnsupportedOperationException - as this GroupList is not modifiable.
Removes an object from the list.
Parameters: o - the object. nothing, as this method always fires a UnsupportedOperation exception. throws: java.lang.UnsupportedOperationException - as this GroupList is not modifiable.