code: private static Locale strip(Locale locale) {
          String language = locale.getLanguage();
          String country = locale.getCountry();
          String variant = locale.getVariant();
          if (!variant.isEmpty()) {
              variant = "";
          } else if (!country.isEmpty()) {
              country = "";
          } else if (!language.isEmpty()) {
              language = "";
          } else {
              return null;
          }
          return new Locale(language, country, variant);
      }
docs: Returns a locale with the most-specific field removed, or null if this
  locale had an empty language, country and variant.