code: public void setEndpoint(String endpoint, String serviceName, String regionId) throws IllegalArgumentException {
          setEndpoint(endpoint);
          signer.setServiceName(serviceName);
          signer.setRegionName(regionId);
      }
docs: Overrides the default endpoint for this client ("http://dynamodb.us-east-1.amazonaws.com/") and explicitly provides
  an AWS region ID and AWS service name to use when the client calculates a signature
  for requests.  In almost all cases, this region ID and service name
  are automatically determined from the endpoint, and callers should use the simpler
  one-argument form of setEndpoint instead of this method.
  <p>
  <b>This method is not threadsafe. Endpoints should be configured when the
  client is created and before any service requests are made. Changing it
  afterwards creates inevitable race conditions for any service requests in
  transit.</b>
  <p>
  Callers can pass in just the endpoint (ex: "dynamodb.us-east-1.amazonaws.com/") or a full
  URL, including the protocol (ex: "http://dynamodb.us-east-1.amazonaws.com/"). If the
  protocol is not specified here, the default protocol from this client's
  {@link ClientConfiguration} will be used, which by default is HTTPS.
  <p>
  For more information on using AWS regions with the AWS SDK for Java, and
  a complete list of all available endpoints for all AWS services, see:
  <a href="http://developer.amazonwebservices.com/connect/entry.jspa?externalID=3912">
  http://developer.amazonwebservices.com/connect/entry.jspa?externalID=3912</a>
  
  @param endpoint
  The endpoint (ex: "dynamodb.us-east-1.amazonaws.com/") or a full URL,
  including the protocol (ex: "http://dynamodb.us-east-1.amazonaws.com/") of
  the region specific AWS endpoint this client will communicate
  with.
  @param serviceName
  The name of the AWS service to use when signing requests.
  @param regionId
  The ID of the region in which this service resides.
  
  @throws IllegalArgumentException
  If any problems are detected with the specified endpoint.
  @see AmazonDynamoDB#setRegion(Region)