THE JAVA COLLECTION FRAMEWORK

A collection is a container of objects

Collection      a collection of elements
List                a sequence of elements 
Set                 a collection of unique elements
SortedSet      a sorted collection of unique elements
Map              a collection of (Key, value) pairs. Keys must be unique
SortedMap   a sorted collection of (Key, value) pairs. Keys must be unique
Iterator         an object that can traverse a collection
ListIterator  an object that can traverse  a sequence

CLASS                                                          INTERFACE

object
   AbstractCollection                                      Collection
        AbstractList                                                List
             AbstractSequentialList
                   LinkedList
             ArrayList
             Vector
                  Stack
        AbstractSet                                                 Set
             HashSet
             TreeSet                                                       SortedSet
   AbstractMap                                              Map
      etc
Note the Hierarchal structure of the classes and the interfaces
and remember the rules of inheritance. Also notice that the names of many of the concrete classes are combinations of the data structure
(Arrays, tree) and the Interface name. By the way, the 4 primary interfaces are Collection, List, Set, and Map  The Iterator is a special
interface that I will discuss later. Below are 3 links that summarize many aspects of the UTIL package and the Collection Framework

http://java.sun.com/j2se/1.4.2/docs/api/java/util/package-summary.html

http://java.sun.com/j2se/1.4.2/docs/guide/collections/overview.html

http://java.sun.com/j2se/1.4.2/docs/guide/collections/reference.html