protected static @Nullable String getProxyString() {
    final HttpConfigurable settings = HttpConfigurable.getInstance();
    if (settings != null && settings.USE_HTTP_PROXY) {
      final String credentials;
      if (settings.PROXY_AUTHENTICATION) {
        credentials = String.format("%s:%s@", settings.getProxyLogin(), settings.getPlainProxyPassword());
      }
      else {
        credentials = "";
      }
      return "http://" + credentials + String.format("%s:%d", settings.PROXY_HOST, settings.PROXY_PORT);
    }
    return null;
  }
protected static @Nullable String getProxyString()