Warm up question: What is the difference between Hashtable and Hashmap?

Notes on Hashtable and Hashmap.

      Both provide key-value access to data.

• HashMap permits null value while Hashtable does not.
• Access to Hashtable is synchronized on the table while access to the HashMap is not (by default).
• Iterator in the HashMap is fail-safe while the enumerator for the Hashtable is not.
• Hashtable is an original collection class in Java while HashMap is part of the new collections framework.