Well I read some where that java.rmi.server.UID().toString can be used to 
generate unique ID's for an application.  Now this class generates a 
unique id as long as the
1)  server's time is never reset backwards. What about when the
  time is set backwards automatically for daylight savings?
2)  The machine takes more than 1 seconds to reboot?

Also I would like to ask that would this uniqueness be maintained if the 
server is restarted.