Following are some difference as :
|1 Hashmap is not synchronized in nature .
||1 Hashtable is synchronised.
|2 iterator in the HashMap is fail-safe .
Fail-safe - “if the Hashtable is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove method, the iterator will throw a ConcurrentModificationException”
|2 while for the Hashtable is not.
|3 HashMap permits null values and only one null key.
||3 while Hashtable doesn't allow key or value as null.
|4 HashMap use iterator.
||4 Hashtable use enumeration.
|5 HashMap is faster.||5 Hashtable is slower.|