code: public void addProgressListener(ProgressListener pListener) {
          if (pListener == null) {
              return;
          }
  
          if (listeners == null) {
              listeners = new CopyOnWriteArrayList<ProgressListener>();
          }
  
          listeners.add(pListener);
      }
docs: Adds a progress listener to this factory.
  
  @param pListener the progress listener