code: public synchronized boolean addDriveListener(final IUSBDriveListener listener) {
          if (listeners.contains(listener)) {
              return false;
          }
  
          listeners.add(listener);
          start();
          return true;
      }
docs: Adds an IUSBDriveListener.
  <p>
  The polling timer is automatically started as needed when a listener is
  added.
  </p>
  
  @param listener the listener to be updated with the attached drives
  @return true if the listener was not in the list and was successfully
  added