code: private static void addSuffixIfAvailable(String messageBundlePath, Set<String> availableLocaleSuffixes,
  			Locale locale, String fileSuffix, ServletContext servletContext) {
  		String localMsgResourcePath = toBundleName(messageBundlePath, locale) + fileSuffix;
  		URL resourceUrl = getResourceBundleURL(localMsgResourcePath, servletContext);
  
  		if (resourceUrl != null) {
  
  			String suffix = localMsgResourcePath.substring(messageBundlePath.length());
  			if (suffix.length() > 0) {
  
  				if (suffix.length() == fileSuffix.length()) {
  					suffix = "";
  				} else {
  					// remove the "_" before the suffix "_en_US" => "en_US"
  					suffix = suffix.substring(1, suffix.length() - fileSuffix.length());
  				}
  			}
  			availableLocaleSuffixes.add(suffix);
  		}
  	}
docs: Adds the locale suffix if the message resource bundle file exists.
  
  @param messageBundlePath
  the message resource bundle path
  @param availableLocaleSuffixes
  the list of available locale suffix to update
  @param locale
  the locale to check.
  @param fileSuffix
  the file suffix