code: public void banUsers(Collection<? extends Jid> jids) throws XMPPErrorException, NoResponseException, NotConnectedException, InterruptedException {
          changeAffiliationByAdmin(jids, MUCAffiliation.outcast);
      }
docs: Bans users from the room. An admin or owner of the room can ban users from a room. This
  means that the banned user will no longer be able to join the room unless the ban has been
  removed. If the banned user was present in the room then he/she will be removed from the
  room and notified that he/she was banned along with the reason (if provided) and the bare
  XMPP user ID of the user who initiated the ban.
  
  @param jids the bare XMPP user IDs of the users to ban.
  @throws XMPPErrorException if an error occurs banning a user. In particular, a
  405 error can occur if a moderator or a user with an affiliation of "owner" or "admin"
  was tried to be banned (i.e. Not Allowed error).
  @throws NoResponseException if there was no response from the server.
  @throws NotConnectedException
  @throws InterruptedException