public void add(ITicket ticket){
  if (tickets.contains(ticket)) {
    return;
  }
  tickets.add(ticket);
  tick|=ticket.shouldTick();
}

public void add ( ITicket ticket ) { if ( tickets . contains ( ticket ) ) { return ; } tickets . add ( ticket ) ; tick |= ticket . shouldTick ( ) ; }
add a ticket to this tickets
