docs: private void fireInvitationRejectionListeners(Message message, MUCUser.Decline rejection) {
          EntityBareJid invitee = rejection.getFrom();
          String reason = rejection.getReason();
          InvitationRejectionListener[] listeners;
          synchronized (invitationRejectionListeners) {
              listeners = new InvitationRejectionListener[invitationRejectionListeners.size()];
              invitationRejectionListeners.toArray(listeners);
          }
          for (InvitationRejectionListener listener : listeners) {
              listener.invitationDeclined(invitee, reason, message, rejection);
          }
      }