我写的sql语句：

Connection conn = DBUtil.getConnection();
        String sql = ""+
                " select * from imooc_goddess where id = ?";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setInt(1, id);

好像没什么问题呀，直接在mysql中可以查出数据，但执行时报错：

Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)

这个”？“有什么问题？