帮我写出对应java代码

好的，以下是针对《实验24.doc》中的各个编程题的Java代码示例：

### 基础训练
#### 调试教材范例
假设教材范例已经调试通过，这里不再重复。

### 编程题
#### 1. 设计字符菜单

import java.util.Scanner;

public class Menu {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean exit = false;
        
        while (!exit) {
            System.out.println("请选择操作:");
            System.out.println("A: 连接数据库");
            System.out.println("B: 插入数据");
            System.out.println("C: 更新数据");
            System.out.println("D: 删除数据");
            System.out.println("Q: 退出");
            
            String choice = scanner.nextLine();
            
            switch (choice.toUpperCase()) {
                case "A":
                    connectDatabase();
                    break;
                case "B":
                    insertData(scanner);
                    break;
                case "C":
                    updateData(scanner);
                    break;
                case "D":
                    deleteData(scanner);
                    break;
                case "Q":
                    exit = true;
                    break;
                default:
                    System.out.println("无效的选择，请重新选择！");
            }
        }
        
        scanner.close();
    }
}

#### 2. 设计静态方法 `connect`

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DatabaseUtils {
    private static final String URL = "jdbc:mysql://210.41.166.73:3306/student";
    private static final String USER = "student";
    private static final String PASSWORD = "student";

    public static void connectDatabase() {
        try (Connection connection = DriverManager.getConnection(URL, USER, PASSWORD)) {
            System.out.println("数据库连接成功！");
        } catch (SQLException e) {
            System.out.println("数据库连接失败：" + e.getMessage());
        }
    }
}

#### 3. 设计静态方法 `insert`

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;

public class DatabaseUtils {
    // ... (其他方法)

    public static void insertData(Scanner scanner) {
        System.out.print("请输入姓名：");
        String name = scanner.nextLine();
        System.out.print("请输入密码：");
        String password = scanner.nextLine();

        String sql = "INSERT INTO users (name, password) VALUES (?, ?)";

        try (Connection connection = DriverManager.getConnection(URL, USER, PASSWORD);
             PreparedStatement statement = connection.prepareStatement(sql)) {
            statement.setString(1, name);
            statement.setString(2, password);
            int rowsAffected = statement.executeUpdate();
            if (rowsAffected > 0) {
                System.out.println("数据插入成功！");
            } else {
                System.out.println("数据插入失败！");
            }
        } catch (SQLException e) {
            System.out.println("数据插入失败：" + e.getMessage());
        }
    }
}

#### 4. 设计静态方法 `update`

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;

public class DatabaseUtils {
    // ... (其他方法)

    public static void updateData(Scanner scanner) {
        System.out.print("请输入新的邮箱：");
        String email = scanner.nextLine();
        System.out.print("请输入新的生日：");
        String birthday = scanner.nextLine();
        System.out.print("请输入要更新的用户名：");
        String name = scanner.nextLine();

        String sql = "UPDATE users SET email = ?, birthday = ? WHERE name = ?";

        try (Connection connection = DriverManager.getConnection(URL, USER, PASSWORD);
             PreparedStatement statement = connection.prepareStatement(sql)) {
            statement.setString(1, email);
            statement.setString(2, birthday);
            statement.setString(3, name);
            int rowsAffected = statement.executeUpdate();
            if (rowsAffected > 0) {
                System.out.println("数据更新成功！");
            } else {
                System.out.println("数据更新失败！");
            }
        } catch (SQLException e) {
            System.out.println("数据更新失败：" + e.getMessage());
        }
    }
}

#### 5. 设计静态方法 `delete`

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.util.Scanner;

public class DatabaseUtils {
    // ... (其他方法)

    public static void deleteData(Scanner scanner) {
        System.out.print("请输入要删除的用户名：");
        String name = scanner.nextLine();

        String sql = "DELETE FROM users WHERE name = ?";

        try (Connection connection = DriverManager.getConnection(URL, USER, PASSWORD);
             PreparedStatement statement = connection.prepareStatement(sql)) {
            statement.setString(1, name);
            int rowsAffected = statement.executeUpdate();
            if (rowsAffected > 0) {
                System.out.println("数据删除成功！");
            } else {
                System.out.println("数据删除失败！");
            }
        } catch (SQLException e) {
            System.out.println("数据删除失败：" + e.getMessage());
        }
    }
}

### 主类整合
将所有方法整合到主类中：

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        boolean exit = false;
        
        while (!exit) {
            System.out.println("请选择操作:");
            System.out.println("A: 连接数据库");
            System.out.println("B: 插入数据");
            System.out.println("C: 更新数据");
            System.out.println("D: 删除数据");
            System.out.println("Q: 退出");
            
            String choice = scanner.nextLine();
            
            switch (choice.toUpperCase()) {
                case "A":
                    DatabaseUtils.connectDatabase();
                    break;
                case "B":
                    DatabaseUtils.insertData(scanner);
                    break;
                case "C":
                    DatabaseUtils.updateData(scanner);
                    break;
                case "D":
                    DatabaseUtils.deleteData(scanner);
                    break;
                case "Q":
                    exit = true;
                    break;
                default:
                    System.out.println("无效的选择，请重新选择！");
            }
        }
        
        scanner.close();
    }
}

这些代码实现了《实验24.doc》中所要求的功能。希望对你有帮助！如果有任何问题，请随时提问。