Differences between HashMap and Hashtable

Both HashMap and Hashtable classes are Map interface implementations . HashMap and Hashtable classes have below defferences based on their functionality and behavior.

HashMap	Hashtable
HashMap is not a legacy class	Hashtable is a legacy class
HashMap is not synchronized. If required HashMap can be synchronized as below: Map m = Collections.synchronizeMap(hashMap);	Hashtable is internally synchronized and can't be unsynchronized. It is thread-safe and can be shared with many threads.
HashMap can contain one null key and multiple null values.	Hashtable cannot contain any null key or null value.
HashMap is not thread-safe, so it is useful for non-threaded applications.	Hashtable is thread-safe, and it can be shared between various threads.
HashMap inherits the AbstractMap class	Hashtable inherits the Dictionary class.
Iterator in the HashMap is fail-safe	Enumerator for the Hashtable is not and throw ConcurrentModificationException
HashMap is fast	Hashtable is slow
HashMap inherits AbstractMap class.	Hashtable inherits Dictionary class.
HashMap is traversed by Iterator.	Hashtable is traversed by Enumerator and Iterator.