code: @Nullable
    public static String searchPropertiesFile(String propertiesFile,
        String[] confPathList) {
      if (propertiesFile == null || confPathList == null) {
        return null;
      }
      for (String path : confPathList) {
        String file = PathUtils.concatPath(path, propertiesFile);
        Properties properties = loadPropertiesFromFile(file);
        if (properties != null) {
          // If a site conf is successfully loaded, stop trying different paths.
          return file;
        }
      }
      return null;
    }
docs: Searches the given properties file from a list of paths.
  
  @param propertiesFile the file to load properties
  @param confPathList a list of paths to search the propertiesFile
  @return the site properties file on success search, or null if failed