code: public boolean isIBMSessionListenerImplemented(ArrayList listeners) {
          for (int i = 0; i < listeners.size(); i++) {
              HttpSessionListener listener = (HttpSessionListener) listeners.get(i);
              if ((listener != null) && (listener instanceof IBMSessionListener)) {
                  return true;
              }
          }
          return false;
      }
docs: /*
  IBM Extension to HttpSessionListener to tell app when a session is removed
  from cache