Java/com/study/demo7/UserServiceMain.java

package com.study.demo7;

import java.io.*;

// 自定义异常
class InvalidUserException extends Exception {
  public InvalidUserException(String message) {
    super(message);
  }
}

// User 类
class User {
  private String name;
  private int age;

  public User(String name, int age) {
    this.name = name;
    this.age = age;
  }

  public String getName() {
    return name;
  }

  public int getAge() {
    return age;
  }
}

// 用户服务类
class UserService {
  public void register(User user) throws InvalidUserException {
    // 校验
    if (user.getName() == null || user.getName().trim().isEmpty()) {
      throw new InvalidUserException("用户名不能为空");
    }
    if (user.getAge() < 0) {
      throw new InvalidUserException("年龄不能为负数");
    }

    // 写入文件
    try (BufferedWriter writer = new BufferedWriter(new FileWriter("users.txt", true))) {
      writer.write("姓名: " + user.getName() + ", 年龄: " + user.getAge());
      writer.newLine();
      System.out.println("用户注册成功，信息已保存");
    } catch (IOException e) {
      System.out.println("用户信息保存失败: " + e.getMessage());
    }
  }
}

// 主类
public class UserServiceMain {
  public static void main(String[] args) {
    UserService service = new UserService();
    User user1 = new User("张三", 25);
    User user2 = new User("李四", -1);

    try {
      service.register(user1);
    } catch (InvalidUserException e) {
      System.out.println("注册失败: " + e.getMessage());
    }

    try {
      service.register(user2);
    } catch (InvalidUserException e) {
      System.out.println("注册失败: " + e.getMessage());
    }
  }
}