update:demo7

com/study/demo7/BankWithdraw.java

@@ -0,0 +1,37 @@
+package com.study.demo7;
+
+// 自定义异常
+class InsufficientBalanceException extends Exception {
+  public InsufficientBalanceException(String message) {
+    super(message);
+  }
+}
+
+// 账户类
+class Account {
+  private double balance;
+
+  public Account(double balance) {
+    this.balance = balance;
+  }
+
+  public void withdraw(double amount) throws InsufficientBalanceException {
+    if (amount > balance) {
+      throw new InsufficientBalanceException("余额不足，当前余额: " + balance);
+    }
+    balance -= amount;
+    System.out.println("取款成功，剩余余额: " + balance);
+  }
+}
+
+// 主类
+public class BankWithdraw {
+  public static void main(String[] args) {
+    Account account = new Account(1000.0);
+    try {
+      account.withdraw(100.0);
+    } catch (InsufficientBalanceException e) {
+      System.out.println("取款失败: " + e.getMessage());
+    }
+  }
+}

com/study/demo7/DivisionCalculator.java

@@ -0,0 +1,24 @@
+package com.study.demo7;
+
+import java.util.Scanner;
+
+public class DivisionCalculator {
+  public static void main(String[] args) {
+    Scanner scanner = new Scanner(System.in);
+    try {
+      System.out.print("请输入第一个整数 a: ");
+      int a = Integer.parseInt(scanner.nextLine());
+      System.out.print("请输入第二个整数 b: ");
+      int b = Integer.parseInt(scanner.nextLine());
+      int result = a / b;
+      System.out.println("结果: " + result);
+    } catch (ArithmeticException e) {
+      System.out.println("错误: 除数不能为 0");
+    } catch (NumberFormatException e) {
+      System.out.println("错误: 请输入有效的整数");
+    } finally {
+      System.out.println("计算结束");
+    }
+    scanner.close();
+  }
+}

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());
+    }
+  }
+}

users.txt

@@ -0,0 +1,2 @@
+姓名: 张三, 年龄: 25
+姓名: 张三, 年龄: 25