code: public static synchronized I18n getI18n(String resource) {
          I18n instance = (I18n)mapping.get(resource);
          if (instance == null) {
              instance = new I18n(ResourceBundle.getBundle(resource,
                                                           Locale.getDefault(),
                                                           getClassLoader()));
              mapping.put(resource, instance);
          }
          return instance;
      }
docs: Retrieve a I18n instance by resource name.
  
  @param resource resource name. See {@link
  ResourceBundle#getBundle(String) ResourceBundle.getBundle()}