Java - Differences between HashMap and Hashtable

HashMap	HashTable
1) HashMap is non synchronized. It is not-thread safe and can't be shared between many threads without proper synchronization code.	Hashtable is synchronized. It is  thread-safe and can be shared with  many threads.
2) HashMapallows one null key and multiple null values.	Hashtabledoesn't allow any null key  or value.
4) HashMap is fast.	Hashtable is slow.
5) We can make the HashMap as synchronized by calling this code Map m = Collections.synchronizedMap(hashMap);	Hashtable is internally synchronized  and can't be unsynchronized.