Difference between HashMap,Hash Set,Hash Table

+++++Differrence between HashMap and Hashtable++++

HashMap and Hashtable both implement java.util.Map interface

    HashMap                                Hashtable
1) HashMap is non synchronized. It is not thread safe.        1) Hashtable is synchronized.It is thread safe and can be shaed with manu threads.
2) HashMap allows one null key and multiple null values        2) Hashtable doesnt allow any null key or value
3) HashMap is a new class introduced in JDK 1.2            3) Hashtable is legacy class
4) HashMap is fast                        4) hASHTABLE is slow
5) We can make HashMap as synchronized by calling
   Map m=Collections.synchronizedMap(hashMap)            5) Hashtable is internally syncronized