code: public static Res use(String baseName, String locale) {
  		String resKey = baseName + locale;
  		Res res = resMap.get(resKey);
  		if (res == null) {
  			res = new Res(baseName, locale);
  			resMap.put(resKey, res);
  		}
  		return res;
  	}
docs: Using the base name and locale to get the Res object, which is used to get i18n message value from the resource file.
  @param baseName the base name to load Resource bundle
  @param locale the locale string like this: "zh_CN" "en_US"
  @return the Res object to get i18n message value