Dao里面怎么修改日期信息

标注的那句话要怎么写

Dao代码

public void UpdateSQuestion(Schoice sc) {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            String url = "jdbc:mysql://127.0.0.1:3306/appoi";
            Connection con = DriverManager.getConnection(url, "root", "123348");

            String sql = "update s_choice set problem=?,optionA =?,optionB=?,optionC=?,optionD=?,answer=?,jointime=? where id=?";
            PreparedStatement cmd = con.prepareStatement(sql);

            cmd.setString(1, sc.getProblem());
            cmd.setString(2, sc.getOptionA());
            cmd.setString(3, sc.getOptionB());
            cmd.setString(4, sc.getOptionC());
            cmd.setString(5, sc.getOptionD());
            cmd.setString(6, sc.getAnswer());
#           cmd.setString(7,sc.getJointime());
            cmd.setInt(8, sc.getId());
            cmd.executeUpdate();
            con.close();

        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        System.out.println("修改单选题信息");
    }

//如果sc.getJointime()返回结果是Date类型就这样
Date date = sc.getJointime();
SimpleDateFormat sf = new SimpleDateFormat("yyyy-MM-dd");
String dateStr = sf.format(date);
cmd.setString(7,dateStr);

//直接把那行换成这段代码