code: @Override
      public void addCongestionListener(CongestionListener listener) {
          this.listeners.add(listener);
  
          CongestionTicket[] ticketsList = getCongestionTicketsList();
          if (ticketsList != null) {
              for (CongestionTicket ticket : ticketsList) {
                  listener.onCongestionStart(ticket);
              }
          }
      }
docs: /*
  (non-Javadoc)
  
  @see org.restcomm.ss7.congestion.CongestionMonitor#addCongestionListener(
  org.restcomm.ss7.congestion.CongestionListener)