Code fragment portions the nodepositionlist class implementing the node list adt with doubly linked list

Code Fragment 6.11: Portions of the
NodePositionList class implementing the node list ADT with a doubly linked list. (Continued from Code Fragments 6.9 and 6.10.) Note that the mechanism used to invalidate a position in the remove method is

A typical computation on an array list, list, or sequence is to march through its elements in order, one at a time, for example, to look for a specific element.

6.3.1 The Iterator and Iterable Abstract Data Types