public static List<UserPermission> getUserPermissions(Connection connection, String tableRegex,
    byte[] columnFamily, String userName) throws Throwable {
    return getUserPermissions(connection, tableRegex, columnFamily, null, userName);
  }
List all the userPermissions matching the given table pattern, column family and user name.
@param connection   Connection
@param tableRegex   The regular expression string to match against. It shouldn't be null, empty
                    or a namespace regular expression.
@param columnFamily Column family
@param userName     User name, if empty then all user permissions will be retrieved.
@return List of UserPermissions
@throws Throwable on failure
hbase-client/src/main/java/org/apache/hadoop/hbase/security/access/AccessControlClient.java