code: public static String getActivationKey(String gatewayAddress, Region activationRegion) throws AmazonClientException {
          return getActivationKey(gatewayAddress, 
                  activationRegion == null ?
                          null : activationRegion.getName());
      }
docs: Sends a request to the AWS Storage Gateway server running at the
  specified address, and returns the activation key for that server.
  
  @param gatewayAddress
  The DNS name or IP address of a running AWS Storage Gateway
  
  @param activationRegionName
  The region in which the gateway will be activated.
  
  @return The activation key required for some API calls to AWS Storage
  Gateway.
  
  @throws AmazonClientException
  If any problems are encountered while trying to contact the
  remote AWS Storage Gateway server.