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) HashMap allows one null key and multiple null values. |
Hashtable doesn't allow any null key or value. |
3) HashMap is a new class introduced in JDK 1.2. |
Hashtable is a legacy class. |
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. |
6) HashMap is traversed by Iterator. |
Hashtable is traversed by Enumerator and Iterator. |
7) Iterator in HashMap is fail-fast. |
Enumerator in Hashtable is not fail-fast. |
8) HashMap inherits AbstractMap class. |
Hashtable inherits Dictionary class. |