finished doubly linkedlist.

Interfaces/Abstract classes (see slides)

Why interface?

Comparable
   Sort example
   problem with mutual comparison!

Design-pattern
Iterator   (smart index with  memory!)
   hasNext()
   next()	
   remove()

ArrayList, LinkedList, and Vector have iterator() method
Why separate iterator() method?

Example: removeLess(Iterator itr, Comparable c)


Abstract classes