When I tried to use the hashtable class, Netbeans gave me an error saying:
While still supported, these classes were made obsolete by the JDK1.2 collection classes, and should probably not be used in new development.
Hashtable
The most direct replacement of a Hashtable is a HashMap.
HashMap
On difference that could be important is that all relevant methods of Hashtable are synchronized while they are not synchronized on HashMap.