code: @GwtIncompatible("incompatible method")
    @Nullable
    public static Locale parseLocaleString(final String localeString) {
      return StringUtils.parseLocaleTokens(localeString,
          StringUtils.tokenizeLocaleSource(localeString));
    }
docs: Parse the given {@code String} representation into a {@link Locale}.
  <p>
  This is the inverse operation of {@link Locale#toString Locale's toString}.
  
  @param localeString the locale {@code String}: following {@code Locale's} {@code toString()}
  format ("en", "en_UK", etc), also accepting spaces as separators (as an alternative to
  underscores)
  <p>
  Note: This variant does not accept the BCP 47 language tag format. Please use
  {@link #parseLocale} for lenient parsing of both formats.
  @return a corresponding {@code Locale} instance, or {@code null} if none
  @throws IllegalArgumentException in case of an invalid locale specification