基于JDK 5.0的collection类的使用总结

HashSet
An unordered collection that rejects duplicates

TreeSet
A sorted set

LinkedHashSet
A set that remembers the order in which elements were inserted
PriorityQueue
A collection that allows efficient removal of the smallest element

HashMap
A data structure that stores key/value associations

treeMap
A map in which the keys are sorted
排序的HashMap
LinkedHashMap
A map that remembers the order in which entries were added