goja-core/src/main/java/goja/core/kits/lang/LocaleKit.java
public static String resolveLocaleCode(String lang, String country, String variant) {
        StringBuilder code = new StringBuilder(lang);
        if (!StringUtils.isEmpty(country)) {
            code.append('_').append(country);
            if (!StringUtils.isEmpty(variant)) {
                code.append('_').append(variant);
            }
        }
        return code.toString();
    }
public static String resolveLocaleCode(String lang, String country, String variant) {
        StringBuilder code = new StringBuilder(lang);
        if (!StringUtils.isEmpty(country)) {
            code.append('_').append(country);
            if (!StringUtils.isEmpty(variant)) {
                code.append('_').append(variant);
            }
        }
        return code.toString();
    }
Transforms locale data to locale code. <code>null</code> values are allowed.