code: public E set(E value, Locale locale) {
      if (defaultLocale == null)
        defaultLocale = locale;
      if (value != null)
        return values.put(locale, value);
      values.remove(locale);
      return null;
    }
docs: Adds or overrides a value to the internal hash.
  
  @param value
  If set to null, removes the value from the internal hash (the local will no longer
  show up in {@link #getAllLocales()}
  @throws NullPointerException
  if locale is null.
  @return The value previously associated with the locale, or null if none.