code: private static void _register (@Nonnull @Nonempty final String sCountryCode, @Nonnull final EContinent... aContinents)
    {
      final Locale aCountry = CountryCache.getInstance ().getCountry (sCountryCode);
      if (s_aMap.containsKey (aCountry))
        throw new IllegalArgumentException ("Country code '" + sCountryCode + "' is already registered!");
      for (final EContinent eContinent : aContinents)
        s_aMap.putSingle (aCountry, eContinent);
    }
docs: Register assignment
  
  @param sCountryCode
  Country code to be used. May not be <code>null</code> nor empty
  @param aContinents
  The enum to be used. May not be <code>null</code> but may contain a
  single <code>null</code> element.