JAVA JDBC mySql预准备语句更新查询

我正在尝试执行以下代码

I am trying to execute the following code

package jdbclesson;

import java.sql.*;

public class PreparedQuery {

public static void main(String[] args) throws Exception
{
    String url              = "jdbc:mysql://localhost:3306/alien?useSSL=false";
    String uname            = "root";
    String pass             = "ma123";
    String query            = "UPDATE student SET username= ? where userid= ? ";
    PreparedStatement stmt  = null;


    Class.forName("com.mysql.jdbc.Driver");
    Connection con = DriverManager.getConnection(url, uname, pass);
    stmt = con.prepareStatement(query);

    stmt.setString(1, "tina");
    stmt.setInt(2, 6);


    int rs = stmt.executeUpdate(query);

    System.out.println(rs);
    stmt.close();
    con.close();

}

}

但出现以下错误

线程主"中的异常 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException:您有一个 您的SQL语法错误；检查与您的手册相对应的手册 MySQL服务器版本附近使用正确的语法吗?在哪里 userid =?在第1行

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 '? where userid=?' at line 1

我的数据库只有一名表生，有2列用户名和用户名，还有10行我缺少的行

My database has only 1 table student with 2 columns userid and username and 10 rows what m i missing