预处理语句

public class Conn {
    static Connection con;
    static PreparedStatement sql;
    static ResultSet res;
    public Connection getConnecvtion() {
        try {
            Class.forName("com.mysql.jdbc.Driver");
            System.out.println("数据库驱动加载成功");
        } catch (ClassNotFoundException e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        try {
//            con = DriverManager.getConnection("jdbc:mysql:" + "//10.21.22.91:3306/demo?useUnicode=true&characterEncoding=UTF-8&useSSL=false&autoReconnect=true&failOverReadOnly=false","root","123456");
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","123456");
            System.out.println("数据库连接成功");
        } catch (SQLException e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        return con;
    }
    
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Conn c = new Conn();
        c.getConnecvtion();
        try {
            sql = con.prepareStatement("select * from tb_stu where id = ?");
            sql.setInt(1, 19);
            res = sql.executeQuery();
            
            
            while (res.next()) {
                String id = res.getString("id");
                String sex = res.getString("sex");
                String birthday = res.getString("birthday");
                System.out.println(birthday);
                String name = res.getString("name");
                System.out.print("编号:"+ id);
                System.out.print("姓名:"+ name);
                System.out.print("性别:"+ sex);
                System.out.println("生日:"+ birthday);
            }
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
    }
}