CSC153 2004S, Class 46: Implementing Lists with Nodes, Revisited

Admin:
* DingDongs
* Picnic
* No homework yet.  Sorry

Overview:
* Linked lists: Implementing lists with nodes.
* Implementing basic methods
* Implementing ordered methods
* Cool tricks

Step one: Look at ListNode.java

Step two: Look at LinkedList.java

Detour:
* Classes extend other classes
* Classes also extend abstract classes (because every abstract class is a class)
* Classes implement interfaces (multiple "inheritance" permitted)
* Interfaces extend other interfaces (multiple "inheritance" permitted)

Detour: 
* Four levels of protection

Move from actual coding to generic coding
* In doubly-linked lists, it makes sense to keep track of the last element as well as the first.
* The previous operation is much easier to implement
  return ((DoublyLinkedNode) pos).prev;
* Deletion is somewhat easier to implement (and certainly more efficient)
  node.prev.next = node.next;
  node.next.prev = node.prev;
  node.next = null;
  node.prev = null;
* What are the problems with this "simple" code?
  * Deleting the first and last elements requires special cases
* Traditional clever trick: Circularly-linked lists
  * One node that is never deleted (comes after the last node and before the first)
  * Next of last is first, prev of first is last.