code: @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);
    }
docs: Get the display name of the passed language in the currently selected UI
  language.
  
  @param aLocale
  The locale from which the display name is required. May be
  <code>null</code>.
  @param aContentLocale
  The locale in which the name of the locale is required. If aLocale
  is "de" and display locale is "de" the result would be "Deutsch"
  whereas if display locale is "en" the result would be "German".
  @return the display name of the language or a fixed text if the passed
  Locale is <code>null</code>, "all" or "independent"
  @see #LOCALE_ALL
  @see #LOCALE_INDEPENDENT