### Question:
LocaleHelper { @Nonnull public static String getLocaleDisplayName (@Nullable final Locale aLocale, @Nonnull final Locale aContentLocale) { ValueEnforcer.notNull (aContentLocale, "ContentLocale"); if (aLocale == null || aLocale.equals (LOCALE_INDEPENDENT)) return ELocaleName.ID_LANGUAGE_INDEPENDENT.getDisplayText (aContentLocale); if (aLocale.equals (LOCALE_ALL)) return ELocaleName.ID_LANGUAGE_ALL.getDisplayText (aContentLocale); return aLocale.getDisplayName (aContentLocale); } private  LocaleHelper(); @Nonnull static String getLocaleDisplayName(@Nullable final Locale aLocale, @Nonnull final Locale aContentLocale); @Nonnull static String getLocaleNativeDisplayName(@Nonnull final Locale aLocale); @Nonnull @ReturnsMutableCopy static ICommonsMap <Locale, String> getAllLocaleDisplayNames(@Nonnull final Locale aContentLocale); @Nonnull @ReturnsImmutableObject @CodingStyleguideUnaware static List <Locale> getCalculatedLocaleListForResolving(@Nonnull final Locale aLocale); @Nonnull static Locale getLocaleFromString(@Nullable final String sLocaleAsString); @Nullable static Locale getLocaleToUseOrNull(@Nonnull final Locale aRequestLocale, @Nonnull final Collection <Locale> aAvailableLocales); @Nullable static Locale getLocaleToUseOrFallback(@Nonnull final Locale aRequestLocale,
                                                 @Nonnull final Collection <Locale> aAvailableLocales,
                                                 @Nullable final Locale aFallback); static boolean isSpecialLocale(@Nullable final Locale aLocale); static boolean isSpecialLocaleCode(@Nullable final String sLocale); @Nullable static String getValidLanguageCode(@Nullable final String sCode); @Nullable static String getValidCountryCode(@Nullable final String sCode); @Nonnull static EChange clearCache(); static final char LOCALE_SEPARATOR; static final String STR_ALL; static final Locale LOCALE_ALL; static final String STR_INDEPENDENT; static final Locale LOCALE_INDEPENDENT; }### Answer:
@Test public void testGetLocaleDisplayName () { assertNotNull (LocaleHelper.getLocaleDisplayName (null, L_DE)); assertNotNull (LocaleHelper.getLocaleDisplayName (LocaleHelper.LOCALE_ALL, L_DE)); assertNotNull (LocaleHelper.getLocaleDisplayName (LocaleHelper.LOCALE_INDEPENDENT, L_DE)); assertNotNull (LocaleHelper.getLocaleDisplayName (L_DE, L_DE)); }