/**
  * @return Returns the User Agent string to be used when communicating with the AWS services. The
  *     User Agent encapsulates SDK, Java, OS and region information.
  */
 public static String getUserAgent() {
   if (userAgent == null) {
     synchronized (VersionInfoUtils.class) {
       if (userAgent == null) initializeUserAgent();
     }
   }
   return userAgent;
 }