What are the differences between a HashMap and a Hashtable in Java?

Question

What are the differences between a HashMap and a Hashtable in Java?

Which is more efficient for non-threaded applications?

Answer 1

Another key difference between hashtable and hashmap is that Iterator in the HashMap is fail-fast while the enumerator for the Hashtable is not and throw ConcurrentModificationException if any other Thread modifies the map structurally by adding or removing any element except Iterator's own remove() method. But this is not a guaranteed behavior and will be done by JVM on best effort."

My source: http://javarevisited.blogspot.com/2010/10/difference-between-hashmap-and.html