LanguageTags.java

import java.util.ArrayList;
import java.util.List;
import java.util.Locale;

public class LanguageTags {

    public static void main(String[] args) {
        Locale[] locales = Locale.getAvailableLocales();
        List<LocaleEntry> entries = new ArrayList<>(locales.length);

        for (Locale locale : locales) {
            if ((locale.getCountry().length() == 2 || locale.getCountry().isEmpty()) && locale.getLanguage().length() == 2) {
                entries.add(
                        new LocaleEntry(
                                locale.getCountry(), locale.getDisplayCountry(),
                                locale.getLanguage(), locale.getDisplayLanguage()));
            }
        }

        entries.sort((a, b) -> {
            int result = a.languageName.compareTo(b.languageName);

            if (result == 0) {
                result = a.countryName.compareTo(b.countryName);

                if (result == 0) {
                    if (a.countryCode.isEmpty() && b.countryCode.isEmpty()) {
                        return 0;
                    }

                    if (a.countryCode.isEmpty()) {
                        return -1;
                    }

                    return 1;
                }

                return result;
            }

            return result;

        });
        entries.forEach(e -> System.out.println(e.toString()));
        entries.forEach(e -> System.out.println(e.toJavaScript()));
    }

}

class LocaleEntry {

    String countryCode;

    String countryName;

    String languageCode;

    String languageName;

    LocaleEntry(String countryCode, String countryName, String languageCode, String languageName) {
        this.countryCode = countryCode;
        this.countryName = countryName;
        this.languageCode = languageCode;
        this.languageName = languageName;
    }

    public String toLanguageTag() {
        if (countryCode.isEmpty()) {
            return languageCode;
        }

        return languageCode + '-' + countryCode;
    }

    @Override
    public String toString() {
        if (countryCode.isEmpty()) {
            return languageName + " (" + languageCode + ")";
        }

        return languageName + " (" + countryName + ") (" + languageCode + "-" + countryCode + ")";
    }

    public String toJavaScript() {
        StringBuilder result = new StringBuilder();

        result.append('{');
        result.append("label:\"");
        result.append(toString());
        result.append("\",");
        result.append("languageTag:\"");
        result.append(toLanguageTag());
        result.append("\",");
        result.append("languageCode:\"");
        result.append(languageCode);
        result.append("\",");
        result.append("languageName:\"");
        result.append(languageName);
        result.append("\",");
        result.append("countryCode:\"");
        result.append(countryCode);
        result.append("\",");
        result.append("countryName:\"");
        result.append(countryName);
        result.append("\"");
        result.append("},");

        return result.toString();
    }

}