关于JDBC 使用 PreparedStatement。用“？占位符出现的sql语法报错的问题，如何解决？

Question

JDBC 使用 PreparedStatement。用“？占位符出现的sql语法报错.为什么会出现报错，“？”使用正确吗，该如何解决

问题相关代码，请勿粘贴截图

package com.itheima.jdbc;

import util.JDBCUtils;

import java.sql.*;
import java.util.Scanner;

public class demo4 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入用户名和密码：");
        String UId = sc.nextLine();
        String Ups = sc.nextLine();

        boolean judge = demo4.load(UId,Ups);
        if(judge)
            System.out.println("登陆成功");
        else
            System.out.println("登陆失败");
    }

    public static boolean load(String UId,String Ups){
        Connection conn = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            conn = JDBCUtils.getConnection();
            String sql = "select * from ip where UId = ? and Ups = ?";
            pstmt = conn.prepareStatement(sql);
            pstmt.setString(1,UId);
            pstmt.setString(2,Ups);
            rs = pstmt.executeQuery(sql);
            return rs.next();

        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JDBCUtils.close(rs,pstmt,conn);
        }
        return false;
    }
}

报错信息
java.sql.SQLSyntaxErrorException: 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 '? and Ups = ?' at line 1

数据库内容，均为varchar类型

Answer 1

所以说，你的报错是啥？