@Override
                    public List<Map<String, String>> load(final String key) throws Exception {
                        final ULocale uLocale = new ULocale(key);
                        final Locale displayLocale = uLocale.toLocale();
                        final List<Map<String, String>> langItems = new ArrayList<>(supportedLanguages.length);

     *
     * @param locale the locale (must not be {@literal null})
     * @return the pattern string for {@link DateFormat#MEDIUM} style
     */
    public static String getMediumPattern(final Locale locale) {
        assertArgumentNotNull("locale", locale);
        return ((SimpleDateFormat) getDateInstance(MEDIUM, locale)).toPattern();
    }

    /**

     *
     * @param locale the locale
     * @return the {@literal locale} if not {@literal null}, otherwise the default locale
     */
    protected static Locale getLocale(final Locale locale) {
        if (locale != null) {
            return locale;
        }
        return LocaleUtil.getDefault();
    }

     *
     * @param locale
     *            Locale
     * @return Separator for decimal numbers
     */
    public static String findDecimalSeparator(final Locale locale) {
        final DecimalFormatSymbols symbol = getDecimalFormatSymbols(locale);
        return Character.toString(symbol.getDecimalSeparator());
    }

    private static DecimalFormatSymbols getDecimalFormatSymbols(final Locale locale) {

    /**
     * Retrieves the current user's locale from the request manager.
     *
     * @return the user's locale, or Locale.ROOT if not available
     */
    private static Locale getUserLocale() {
        final Locale locale = ComponentUtil.getRequestManager().getUserLocale();
        if (locale == null) {
            return Locale.ROOT;
        }
        return locale;
    }

    /**

     *
     * @param locale
     *            Locale. Must not be {@literal null}.
     * @return the pattern string for {@link DateFormat#MEDIUM} style
     */
    public static String getMediumPattern(final Locale locale) {
        assertArgumentNotNull("locale", locale);
        return ((SimpleDateFormat) getTimeInstance(MEDIUM, locale)).toPattern();
    }

    /**

     *
     * @param locale
     *            Locale. Must not be {@literal null}.
     * @return the pattern string for {@link DateFormat#MEDIUM} style
     */
    public static String getMediumPattern(final Locale locale) {
        assertArgumentNotNull("locale", locale);
        return ((SimpleDateFormat) getDateTimeInstance(MEDIUM, MEDIUM, locale)).toPattern();
    }

    /**

     *
     * @param s
     *            A string representing a number
     * @param locale
     *            The locale. Must not be {@literal null}.
     * @return The normalized string
     */
    public static String normalize(final String s, final Locale locale) {
        assertArgumentNotNull("locale", locale);

        if (s == null) {
            return null;
        }

import static org.junit.Assert.assertThat;

import java.util.Locale;

import org.codelibs.core.misc.LocaleUtil;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

/**
 * @author wyukawa
 *
 */
public class NullArgumentExceptionTest {

    @Before
    public void setUp() throws Exception {
        LocaleUtil.setDefault(() -> Locale.JAPANESE);
    }

    @After

# Access: http://localhost:8080/admin/?browser_lang=sv
```

## Troubleshooting

### Language doesn't appear in dropdown

- Verify both `fess_label_[locale].properties` and `fess_message_[locale].properties` exist
- Check that locale code is in `supported.languages` in `fess_config.properties`
- Regenerate Java classes: `mvn dbflute:freegen`
- Rebuild project: `mvn clean package`
- Restart Fess application