public void deleteUser(int userId) {
        DataContext dc = DataContext.createDataContext();

        Expression qualifier2 = ExpressionFactory.matchExp(
                User.USER_ID_PROPERTY,
                String.valueOf(userId));

        SelectQuery select2 = new SelectQuery(User.class, qualifier2);
        List userList = dc.performQuery(select2);

        if (userList.size() == 0) {
            throw new IllegalArgumentException("user does not exist: " + userList);
        }

        User u = (User)userList.get(0);
        if (u.getType().equalsIgnoreCase("admin")) {
            throw new IllegalArgumentException(" Cannot delete admin");
        }