A DESCRIPTION OF THE PROBLEM :
The text "This interface extends ListDataModel and adds the concept of a selected item" is not correct, as from what I kind see is that the ComboBoxModel derives from ListModel

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
It should (probably) say "This interface extends ListModel and adds the concept of a selected item"
ACTUAL -
"This interface extends ListDataModel and adds the concept of a selected item..."

URL OF FAULTY DOCUMENTATION :
http://java.sun.com/j2se/1.5.0/docs/api/javax/swing/ComboBoxModel.html