code: public static boolean saveStaticResolutions(Configuration conf) {
      List<String[]> staticResolutions = NetUtils.getAllStaticResolutions();
      if (staticResolutions != null && staticResolutions.size() > 0) {
        StringBuffer str = new StringBuffer();
  
        for (int i = 0; i < staticResolutions.size(); i++) {
          String[] hostToResolved = staticResolutions.get(i);
          str.append(hostToResolved[0]+"="+hostToResolved[1]);
          if (i != staticResolutions.size() - 1) {
            str.append(',');
          }
        }
        conf.set("hadoop.net.static.resolutions", str.toString());
        return true;
      }
      return false;
    }
docs: Save the static resolutions to configuration. This is required for junit
  to work on testcases that simulate multiple nodes on a single physical
  node.
  @param conf The configuration
  @return A boolean indicating if the configuration was modified.