import java.sql.*;
public class Main {
    public static void main(String[] args) {
        // 修改用户名和密码
        System.out.println("请输入要修改的用户名");
        Scanner sc = new Scanner(System.in);
        String yonghuming = sc.next();
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            String url = "jdbc:mysql://localhost:3306/s0822";
            String user = "root";
            String password = "1234";
            Connection c = DriverManager.getConnection(url, user, password);
            String sql = "SELECT * FROM user WHERE username = ?";
            PreparedStatement p = c.prepareStatement(sql);
            p.setString(1, yonghuming);
            ResultSet rs = p.executeQuery();
            if (rs.next()) {
                System.out.println("请输入你想更改的用户名");
                String newusername = sc.next();
                String sql01 = "UPDATE user set username = ? WHERE username = ?";
                PreparedStatement updateStmt = c.prepareStatement(sql01);
                updateStmt.setString(1, newusername);
                updateStmt.setString(2, yonghuming);
                int affectedRows = updateStmt.executeUpdate();
                if (affectedRows > 0) {
                    System.out.println("恭喜你，账户名成功修改为" + newusername);
                } else {
                    System.out.println("用户名更新失败");
                }
            } else {
                System.out.println("用户名不存在");
            }
        } catch (ClassNotFoundException e) {
            System.out.println("找不到JDBC驱动类");
            e.printStackTrace();
        } catch (SQLException e) {
            System.out.println("数据库操作出错");
            e.printStackTrace();
        } finally {
            sc.close();
        }
    }
}