code: public void setSourceDirectory (final File directory)
    {
      if (!directory.isAbsolute ())
      {
        throw new IllegalArgumentException ("source directory is not absolute: " + directory);
      }
      this.scanner.setBasedir (directory);
    }
docs: Sets the absolute path to the source directory to scan for grammar files.
  This directory must exist or the scanner will report an error.
  
  @param directory
  The absolute path to the source directory to scan, must not be
  <code>null</code>.