code: public void setConfigFile(final String config) {
          if (config == null) {
              throw (new IllegalArgumentException(
                      "Configuration file parameter is null"));
          }
          File file = new File(config);
          if (file.exists()) {
              if (file.isDirectory()) {
                  throw new IllegalArgumentException("Folder " + config
                          + " is not a configuration file");
              }
          } else {
              throw new IllegalArgumentException("Configuration file " + config
                      + " not found");
          }
          setConfigFile(file);
      }
docs: Check the config parameter and keep it only if it is valid.
  
  @param config a file name (relative or absolute)