code: protected DirectoryManager cloneDirectoryManager(DirectoryManager directoryManager, String suffix) throws IOException
     {
        try
        {
           DirectoryManager df =  directoryManager.getClass().newInstance();
           df.init(this.path + suffix);
           return df;
        }
        catch (IOException e)
        {
           throw e;
        }
        catch (Exception e)
        {
           IOException ex = new IOException();
           ex.initCause(e);
           throw ex;
        }
     }
docs: Clone the default Index directory manager
  @return an initialized {@link DirectoryManager}.
  @throws IOException
  if the directory manager cannot be instantiated or an
  exception occurs while initializing the manager.