public static String getPrimaryGroupName(String userName, AlluxioConfiguration conf)
      throws IOException {
    List<String> groups = getGroups(userName, conf);
    return (groups != null && groups.size() > 0) ? groups.get(0) : "";
  }
public static String getPrimaryGroupName ( String userName , AlluxioConfiguration conf ) throws IOException { List < String > groups = getGroups ( userName , conf ) ; return ( groups != null && groups . size ( ) > 0 ) ? groups . get ( 0 ) : "" ; }
Gets the primary group name of a user.

@param userName Alluxio user name
@param conf Alluxio configuration
@return primary group name