public void addAllowedUser(String user) {
    if (StringUtils.isBlank(user)) {
      return;
    }
    if (allowedUsers.contains(WILDCARD_ACL_VALUE)) {
      return;
    }
    if (user.equals(WILDCARD_ACL_VALUE)) {
      allowedUsers.clear();
      allowedGroups.clear();
    }
    allowedUsers.add(user);
  }
Parser for extracting ACL information from Configs
common/src/java/org/apache/hive/common/util/ACLConfigurationParser.java