update:demo7

com/study/demo7/UserServiceMain.java

@@ -0,0 +1,72 @@
+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());
+    }
+  }
+}