-locale option issues:
Language length is limited by 2 symbols (see jdk.javadoc.internal.tool.Start.getLocale(String localeName)):
        ............................................................
        } else if (firstuscore == -1 && localeName.length() == 2) {
            language = localeName;
        } else {
            usageError("main.malformed_locale_name", localeName);
        ............................................................
Incorrect code in searchLocale() method:
       for (Locale loc : Locale.getAvailableLocales()) {
            if (loc.getLanguage().equals(language) &&
                (country == null || loc.getCountry().equals(country)) &&
                (variant == null || loc.getVariant().equals(variant))) {
                return loc;
            }
            ............................................................
The country code of the "loc" variable is ignored so the "en_US" locale can be selected instead of "US".

(Probably it would be better to use Locale.forLanguageTag(String)).