code: public Occupant getOccupant(EntityFullJid user) {
          Presence presence = getOccupantPresence(user);
          if (presence != null) {
              return new Occupant(presence);
          }
          return null;
      }
docs: Returns the Occupant information for a particular occupant, or <tt>null</tt> if the
  user is not in the room. The Occupant object may include information such as full
  JID of the user as well as the role and affiliation of the user in the room.<p>
  
  @param user the room occupant to search for his presence. The format of user must
  be: roomName@service/nickname (e.g. darkcave@macbeth.shakespeare.lit/thirdwitch).
  @return the Occupant or <tt>null</tt> if the user is unavailable (i.e. not in the room).