diff --git a/src/JuniorQuestionGenerator.java b/src/JuniorQuestionGenerator.java
index eaad998..e18a9c1 100644
--- a/src/JuniorQuestionGenerator.java
+++ b/src/JuniorQuestionGenerator.java
@@ -5,32 +5,32 @@ import java.util.Random;
  * 生成适合初中生的数学题目，包含平方和开根号运算
  */
 public class JuniorQuestionGenerator implements QuestionGenerator {
-    @Override
-    public String generateQuestion(StringBuilder question, Random random) {
-        // 确保所有初中题目都包含至少一个平方或开根号的运算符
-        int num = random.nextInt(100) + 1;
-        boolean isSquare = random.nextBoolean();
+  @Override
+  public String generateQuestion(StringBuilder question, Random random) {
+    // 确保所有初中题目都包含至少一个平方或开根号的运算符
+    int num = random.nextInt(100) + 1;
+    boolean isSquare = random.nextBoolean();
 
-        if (isSquare) {
-            // 生成平方题
-            question.append(num).append("^2");
-        } else {
-            // 生成开根号题，确保是完全平方数
-            int sqrtNum = random.nextInt(10) + 1;
-            num = sqrtNum * sqrtNum;
-            question.append("√").append(num);
-        }
-
-        // 添加一些其他运算符使题目更复杂
-        int complexity = random.nextInt(2) + 1;
-        for (int i = 0; i < complexity; i++) {
-            String[] operators = {"+", "-", "*"};
-            String op = operators[random.nextInt(operators.length)];
-            int addNum = random.nextInt(10) + 1;
-            question.append(" ").append(op).append(" ").append(addNum);
-        }
+    if (isSquare) {
+      // 生成平方题
+      question.append(num).append("^2");
+    } else {
+      // 生成开根号题，确保是完全平方数
+      int sqrtNum = random.nextInt(10) + 1;
+      num = sqrtNum * sqrtNum;
+      question.append("√").append(num);
+    }
 
-        question.append(" = ?");
-        return question.toString();
+    // 添加一些其他运算符使题目更复杂
+    int complexity = random.nextInt(2) + 1;
+    for (int i = 0; i < complexity; i++) {
+      String[] operators = {"+", "-", "*"};
+      String op = operators[random.nextInt(operators.length)];
+      int addNum = random.nextInt(10) + 1;
+      question.append(" ").append(op).append(" ").append(addNum);
     }
+
+    question.append(" = ?");
+    return question.toString();
+  }
 }
\ No newline at end of file
diff --git a/src/MathExamGenerator.class b/src/MathExamGenerator.class
index a2c4882..909c0b1 100644
Binary files a/src/MathExamGenerator.class and b/src/MathExamGenerator.class differ
diff --git a/src/MathExamGenerator.java b/src/MathExamGenerator.java
index 956555a..5a173be 100644
--- a/src/MathExamGenerator.java
+++ b/src/MathExamGenerator.java
@@ -9,300 +9,300 @@ import java.util.*;
  * 主类，负责用户登录、题目生成和文件操作
  */
 public class MathExamGenerator {
-    // 预设的用户账号信息
-    private static final Map<String, UserInfo> USER_ACCOUNTS = new HashMap<>();
-
-    // 当前登录用户信息
-    private static UserInfo currentUser = null;
-    // 已生成的题目集，用于检查重复
-    private static final Set<String> generatedQuestions = new HashSet<>();
-
-    private static boolean isRunning = true;
-
-    static {
-        // 初始化小学、初中和高中各三个账号
-        // 小学账户
-        USER_ACCOUNTS.put("张三1", new UserInfo("张三1", "123", "小学"));
-        USER_ACCOUNTS.put("张三2", new UserInfo("张三2", "123", "小学"));
-        USER_ACCOUNTS.put("张三3", new UserInfo("张三3", "123", "小学"));
-
-        // 初中账户
-        USER_ACCOUNTS.put("李四1", new UserInfo("李四1", "123", "初中"));
-        USER_ACCOUNTS.put("李四2", new UserInfo("李四2", "123", "初中"));
-        USER_ACCOUNTS.put("李四3", new UserInfo("李四3", "123", "初中"));
-
-        // 高中账户
-        USER_ACCOUNTS.put("王五1", new UserInfo("王五1", "123", "高中"));
-        USER_ACCOUNTS.put("王五2", new UserInfo("王五2", "123", "高中"));
-        USER_ACCOUNTS.put("王五3", new UserInfo("王五3", "123", "高中"));
-    }
-
-    public static void main(String[] args) {
-        // 使用BufferedReader配合InputStreamReader，明确指定GBK编码
-        try (BufferedReader reader = new BufferedReader(
-                new InputStreamReader(System.in, Charset.forName("GBK")))) {
-
-            System.out.println("欢迎使用中小学数学卷子自动生成程序");
-            System.out.println("请使用您的账号和密码登录（格式：用户名 密码）");
-
-            while (isRunning) {
-                if (currentUser == null) {
-                    handleLogIn(reader);
-                } else {
-                    handleRequirement(reader);
-                }
-            }
-        } catch (IOException e) {
-            System.out.println("输入输出错误：" + e.getMessage());
-        }
-    }
-    public static void handleLogIn(BufferedReader reader) throws IOException {
-        // 用户未登录，显示登录提示
-        System.out.print("请输入用户名和密码（用空格隔开,输入exit退出）：");
-        String input = reader.readLine();
-
-        if (input == null || input.trim().isEmpty()) {
-            System.out.println("输入不能为空，请重新输入");
-            return;
-        } else if (input.equals("exit")) {
-            isRunning = false;
-            return;
-        }
-
-        String[] parts = input.split(" ");
-
-        if (parts.length == 2) {
-            String username = parts[0];
-            String password = parts[1];
-            // 验证用户登录
-            boolean loginSuccess = false;
-            for (Map.Entry<String, UserInfo> entry : USER_ACCOUNTS.entrySet()) {
-                if (entry.getValue().getUsername().equals(username) &&
-                        entry.getValue().getPassword().equals(password)) {
-                    currentUser = entry.getValue();
-                    loginSuccess = true;
-                    break;
-                }
-            }
-            if (loginSuccess) {
-                System.out.println("登录成功！当前选择为" + currentUser.getUserType() + "出题");
-                System.out.println("提示：您可以输入'切换为小学'、'切换为初中'或'切换为高中'来切换题目难度");
-                handleUserChoice();
-                loadExistingQuestions();
-            } else {
-                System.out.println("登录失败，请输入正确的用户名和密码");
-            }
+  // 预设的用户账号信息
+  private static final Map<String, UserInfo> USER_ACCOUNTS = new HashMap<>();
+
+  // 当前登录用户信息
+  private static UserInfo currentUser = null;
+  // 已生成的题目集，用于检查重复
+  private static final Set<String> generatedQuestions = new HashSet<>();
+
+  private static boolean isRunning = true;
+
+  static {
+    // 初始化小学、初中和高中各三个账号
+    // 小学账户
+    USER_ACCOUNTS.put("张三1", new UserInfo("张三1", "123", "小学"));
+    USER_ACCOUNTS.put("张三2", new UserInfo("张三2", "123", "小学"));
+    USER_ACCOUNTS.put("张三3", new UserInfo("张三3", "123", "小学"));
+
+    // 初中账户
+    USER_ACCOUNTS.put("李四1", new UserInfo("李四1", "123", "初中"));
+    USER_ACCOUNTS.put("李四2", new UserInfo("李四2", "123", "初中"));
+    USER_ACCOUNTS.put("李四3", new UserInfo("李四3", "123", "初中"));
+
+    // 高中账户
+    USER_ACCOUNTS.put("王五1", new UserInfo("王五1", "123", "高中"));
+    USER_ACCOUNTS.put("王五2", new UserInfo("王五2", "123", "高中"));
+    USER_ACCOUNTS.put("王五3", new UserInfo("王五3", "123", "高中"));
+  }
+
+  public static void main(String[] args) {
+    // 使用BufferedReader配合InputStreamReader，明确指定GBK编码
+    try (BufferedReader reader = new BufferedReader(
+        new InputStreamReader(System.in, Charset.forName("GBK")))) {
+
+      System.out.println("欢迎使用中小学数学卷子自动生成程序");
+      System.out.println("请使用您的账号和密码登录（格式：用户名 密码）");
+
+      while (isRunning) {
+        if (currentUser == null) {
+          handleLogIn(reader);
         } else {
-            System.out.println("输入格式错误，请用空格分隔用户名和密码");
+          handleRequirement(reader);
         }
+      }
+    } catch (IOException e) {
+      System.out.println("输入输出错误：" + e.getMessage());
     }
-    private static void handleRequirement(BufferedReader reader) throws IOException {
-        // 用户已登录，显示题目数量输入提示
-        System.out.print("准备生成" + currentUser.getUserType() +
-                "数学题目，请输入生成题目数量（输入-1将退出当前用户，重新登录）：");
-        String input = reader.readLine();
-        if (input == null || input.trim().isEmpty()) {
-            return;
-        }
-        // 检查是否为切换类型命令
-        if (input.startsWith("切换为")) {
-            String targetType = input.substring(3).trim();
-            if ("小学".equals(targetType) || "初中".equals(targetType) || "高中".equals(targetType)) {
-                currentUser.setUserType(targetType);
-                System.out.println("切换成功！准备生成" + currentUser.getUserType() + "数学题目，请输入生成题目数量");
-            } else {
-                System.out.println("切换类型错误，请输入'切换为小学'、'切换为初中'或'切换为高中'");
-            }
-            return;
-        }
-
-        try {
-            int questionCount = Integer.parseInt(input);
-
-            if (questionCount == -1) {
-                // 退出登录
-                currentUser = null;
-                generatedQuestions.clear();
-                System.out.println("已退出登录");
-            } else if (questionCount >= 10 && questionCount <= 30) {
-                // 生成题目
-                generateExam(questionCount);
-            } else {
-                System.out.println("题目数量必须在10-30之间");
-            }
-        } catch (NumberFormatException e) {
-            System.out.println("请输入有效的数字");
-        }
+  }
+  public static void handleLogIn(BufferedReader reader) throws IOException {
+    // 用户未登录，显示登录提示
+    System.out.print("请输入用户名和密码（用空格隔开,输入exit退出）：");
+    String input = reader.readLine();
+
+    if (input == null || input.trim().isEmpty()) {
+      System.out.println("输入不能为空，请重新输入");
+      return;
+    } else if (input.equals("exit")) {
+      isRunning = false;
+      return;
     }
-    // 生成试卷
-    private static void generateExam(int questionCount) {
-        List<String> questions = generateUniqueQuestions(questionCount);
 
-        // 保存试卷到文件
-        saveExamToFile(questions);
-
-        System.out.println("已成功生成" + questions.size() + "道" + currentUser.getUserType() + "数学题目");
+    String[] parts = input.split(" ");
+
+    if (parts.length == 2) {
+      String username = parts[0];
+      String password = parts[1];
+      // 验证用户登录
+      boolean loginSuccess = false;
+      for (Map.Entry<String, UserInfo> entry : USER_ACCOUNTS.entrySet()) {
+        if (entry.getValue().getUsername().equals(username) &&
+            entry.getValue().getPassword().equals(password)) {
+          currentUser = entry.getValue();
+          loginSuccess = true;
+          break;
+        }
+      }
+      if (loginSuccess) {
+        System.out.println("登录成功！当前选择为" + currentUser.getUserType() + "出题");
+        System.out.println("提示：您可以输入'切换为小学'、'切换为初中'或'切换为高中'来切换题目难度");
         handleUserChoice();
+        loadExistingQuestions();
+      } else {
+        System.out.println("登录失败，请输入正确的用户名和密码");
+      }
+    } else {
+      System.out.println("输入格式错误，请用空格分隔用户名和密码");
     }
-
-    // 生成不重复的题目
-    private static List<String> generateUniqueQuestions(int questionCount) {
-        List<String> questions = new ArrayList<>();
-        Random random = new Random();
-        int attempts = 0;
-        int maxAttempts = questionCount * 3; // 最多尝试次数，避免死循环
-
-        while (questions.size() < questionCount && attempts < maxAttempts) {
-            String question = generateQuestion();
-            if (!generatedQuestions.contains(question)) {
-                questions.add(question);
-                generatedQuestions.add(question);
-            }
-            attempts++;
-        }
-
-        return questions;
+  }
+  private static void handleRequirement(BufferedReader reader) throws IOException {
+    // 用户已登录，显示题目数量输入提示
+    System.out.print("准备生成" + currentUser.getUserType() +
+        "数学题目，请输入生成题目数量（输入-1将退出当前用户，重新登录）：");
+    String input = reader.readLine();
+    if (input == null || input.trim().isEmpty()) {
+      return;
+    }
+    // 检查是否为切换类型命令
+    if (input.startsWith("切换为")) {
+      String targetType = input.substring(3).trim();
+      if ("小学".equals(targetType) || "初中".equals(targetType) || "高中".equals(targetType)) {
+        currentUser.setUserType(targetType);
+        System.out.println("切换成功！准备生成" + currentUser.getUserType() + "数学题目，请输入生成题目数量");
+      } else {
+        System.out.println("切换类型错误，请输入'切换为小学'、'切换为初中'或'切换为高中'");
+      }
+      return;
     }
 
-    // 处理用户生成试卷后的选择
-    private static void handleUserChoice() {
-        System.out.println("请选择：");
-        System.out.println("1. 生成题目");
-        System.out.println("2. 切换题目难度");
-        System.out.println("3. 退出当前用户");
-        System.out.println("4. 退出程序");
-
-        try {
-            BufferedReader reader = new BufferedReader(
-                    new InputStreamReader(System.in, Charset.forName("GBK")));
-            String choice = reader.readLine();
-
-            switch (choice) {
-                case "2":
-                    handleDifficultySwitch();
-                    break;
-                case "3":
-                    currentUser = null;
-                    generatedQuestions.clear();
-                    System.out.println("已退出登录");
-                    break;
-                case "1":
-                    break;
-                case "4":
-                    isRunning = false;
-                    break;
-                default:
-                    System.out.println("无效的选项，请重新输入");
-                    handleUserChoice();
-                    break;
-            }
-        } catch (IOException e) {
-            System.out.println("输入错误：" + e.getMessage());
-        }
+    try {
+      int questionCount = Integer.parseInt(input);
+
+      if (questionCount == -1) {
+        // 退出登录
+        currentUser = null;
+        generatedQuestions.clear();
+        System.out.println("已退出登录");
+      } else if (questionCount >= 10 && questionCount <= 30) {
+        // 生成题目
+        generateExam(questionCount);
+      } else {
+        System.out.println("题目数量必须在10-30之间");
+      }
+    } catch (NumberFormatException e) {
+      System.out.println("请输入有效的数字");
     }
+  }
+  // 生成试卷
+  private static void generateExam(int questionCount) {
+    List<String> questions = generateUniqueQuestions(questionCount);
 
-    // 处理难度切换
-    private static void handleDifficultySwitch() {
-        try {
-            BufferedReader reader = new BufferedReader(
-                    new InputStreamReader(System.in, Charset.forName("GBK")));
-
-            while (true) {
-                System.out.print("请输入目标难度（小学/初中/高中）：");
-                String targetType = reader.readLine();
-
-                if ("小学".equals(targetType) || "初中".equals(targetType) || "高中".equals(targetType)) {
-                    currentUser.setUserType(targetType);
-                    System.out.println("已切换为" + targetType + "难度");
-                    break;
-                } else {
-                    System.out.println("难度类型错误，请重新输入");
-                }
-            }
-        } catch (IOException e) {
-            System.out.println("输入错误：" + e.getMessage());
-        }
+    // 保存试卷到文件
+    saveExamToFile(questions);
+
+    System.out.println("已成功生成" + questions.size() + "道" + currentUser.getUserType() + "数学题目");
+    handleUserChoice();
+  }
+
+  // 生成不重复的题目
+  private static List<String> generateUniqueQuestions(int questionCount) {
+    List<String> questions = new ArrayList<>();
+    Random random = new Random();
+    int attempts = 0;
+    int maxAttempts = questionCount * 3; // 最多尝试次数，避免死循环
+
+    while (questions.size() < questionCount && attempts < maxAttempts) {
+      String question = generateQuestion();
+      if (!generatedQuestions.contains(question)) {
+        questions.add(question);
+        generatedQuestions.add(question);
+      }
+      attempts++;
     }
 
-    // 根据用户类型获取对应的题目生成器
-    private static QuestionGenerator getQuestionGenerator() {
-        if ("小学".equals(currentUser.getUserType())) {
-            return new PrimaryQuestionGenerator();
-        } else if ("初中".equals(currentUser.getUserType())) {
-            return new JuniorQuestionGenerator();
-        } else if ("高中".equals(currentUser.getUserType())) {
-            return new SeniorQuestionGenerator();
+    return questions;
+  }
+
+  // 处理用户生成试卷后的选择
+  private static void handleUserChoice() {
+    System.out.println("请选择：");
+    System.out.println("1. 生成题目");
+    System.out.println("2. 切换题目难度");
+    System.out.println("3. 退出当前用户");
+    System.out.println("4. 退出程序");
+
+    try {
+      BufferedReader reader = new BufferedReader(
+          new InputStreamReader(System.in, Charset.forName("GBK")));
+      String choice = reader.readLine();
+
+      switch (choice) {
+        case "2":
+          handleDifficultySwitch();
+          break;
+        case "3":
+          currentUser = null;
+          generatedQuestions.clear();
+          System.out.println("已退出登录");
+          break;
+        case "1":
+          break;
+        case "4":
+          isRunning = false;
+          break;
+        default:
+          System.out.println("无效的选项，请重新输入");
+          handleUserChoice();
+          break;
+      }
+    } catch (IOException e) {
+      System.out.println("输入错误：" + e.getMessage());
+    }
+  }
+
+  // 处理难度切换
+  private static void handleDifficultySwitch() {
+    try {
+      BufferedReader reader = new BufferedReader(
+          new InputStreamReader(System.in, Charset.forName("GBK")));
+
+      while (true) {
+        System.out.print("请输入目标难度（小学/初中/高中）：");
+        String targetType = reader.readLine();
+
+        if ("小学".equals(targetType) || "初中".equals(targetType) || "高中".equals(targetType)) {
+          currentUser.setUserType(targetType);
+          System.out.println("已切换为" + targetType + "难度");
+          break;
+        } else {
+          System.out.println("难度类型错误，请重新输入");
         }
-        return null;
+      }
+    } catch (IOException e) {
+      System.out.println("输入错误：" + e.getMessage());
     }
+  }
+
+  // 根据用户类型获取对应的题目生成器
+  private static QuestionGenerator getQuestionGenerator() {
+    if ("小学".equals(currentUser.getUserType())) {
+      return new PrimaryQuestionGenerator();
+    } else if ("初中".equals(currentUser.getUserType())) {
+      return new JuniorQuestionGenerator();
+    } else if ("高中".equals(currentUser.getUserType())) {
+      return new SeniorQuestionGenerator();
+    }
+    return null;
+  }
 
-    // 根据用户类型生成题目
-    private static String generateQuestion() {
-        StringBuilder question = new StringBuilder();
-        Random random = new Random();
-        QuestionGenerator generator = getQuestionGenerator();
-
-        if (generator != null) {
-            return generator.generateQuestion(question, random);
-        }
+  // 根据用户类型生成题目
+  private static String generateQuestion() {
+    StringBuilder question = new StringBuilder();
+    Random random = new Random();
+    QuestionGenerator generator = getQuestionGenerator();
 
-        return "题目生成错误";
+    if (generator != null) {
+      return generator.generateQuestion(question, random);
     }
 
-    // 加载已存在的题目，避免重复
-    private static void loadExistingQuestions() {
-        if (currentUser == null) return;
-        try {
-            String userDir = currentUser.getUsername();
-            File dir = new File(userDir);
-
-            if (dir.exists() && dir.isDirectory()) {
-                File[] files = dir.listFiles();
-                if (files != null) {
-                    for (File file : files) {
-                        if (file.isFile() && file.getName().endsWith(".txt")) {
-                            try (BufferedReader reader = new BufferedReader(
-                                    new InputStreamReader(new FileInputStream(file), Charset.forName("GBK")))) {
-                                String line;
-                                while ((line = reader.readLine()) != null) {
-                                    line = line.trim();
-                                    if (!line.isEmpty() && !line.matches("^\\d+\\.")) {
-                                        generatedQuestions.add(line);
-                                    }
-                                }
-                            }
-                        }
-                    }
+    return "题目生成错误";
+  }
+
+  // 加载已存在的题目，避免重复
+  private static void loadExistingQuestions() {
+    if (currentUser == null) return;
+    try {
+      String userDir = currentUser.getUsername();
+      File dir = new File(userDir);
+
+      if (dir.exists() && dir.isDirectory()) {
+        File[] files = dir.listFiles();
+        if (files != null) {
+          for (File file : files) {
+            if (file.isFile() && file.getName().endsWith(".txt")) {
+              try (BufferedReader reader = new BufferedReader(
+                  new InputStreamReader(new FileInputStream(file), Charset.forName("GBK")))) {
+                String line;
+                while ((line = reader.readLine()) != null) {
+                  line = line.trim();
+                  if (!line.isEmpty() && !line.matches("^\\d+\\.")) {
+                    generatedQuestions.add(line);
+                  }
                 }
+              }
             }
-        } catch (IOException e) {
-            System.out.println("加载已存在题目时出错：" + e.getMessage());
+          }
         }
+      }
+    } catch (IOException e) {
+      System.out.println("加载已存在题目时出错：" + e.getMessage());
     }
-
-    // 保存试卷到文件
-    private static void saveExamToFile(List<String> questions) {
-        try {
-            // 创建用户目录（相对路径）
-            String userDir = currentUser.getUsername();
-            Files.createDirectories(Paths.get(userDir));
-
-            // 生成文件名：年-月-日-时-分-秒.txt
-            String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
-            String filePath = userDir + File.separator + timestamp + ".txt";
-
-            try (BufferedWriter writer = new BufferedWriter(
-                    new OutputStreamWriter(new FileOutputStream(filePath), Charset.forName("GBK")))) {
-                for (int i = 0; i < questions.size(); i++) {
-                    writer.write((i + 1) + ". " + questions.get(i));
-                    writer.newLine();
-                    if (i < questions.size() - 1) {
-                        writer.newLine(); // 题目之间空一行
-                    }
-                }
-            }
-        } catch (IOException e) {
-            System.out.println("保存试卷时出错：" + e.getMessage());
+  }
+
+  // 保存试卷到文件
+  private static void saveExamToFile(List<String> questions) {
+    try {
+      // 创建用户目录（相对路径）
+      String userDir = currentUser.getUsername();
+      Files.createDirectories(Paths.get(userDir));
+
+      // 生成文件名：年-月-日-时-分-秒.txt
+      String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
+      String filePath = userDir + File.separator + timestamp + ".txt";
+
+      try (BufferedWriter writer = new BufferedWriter(
+          new OutputStreamWriter(new FileOutputStream(filePath), Charset.forName("GBK")))) {
+        for (int i = 0; i < questions.size(); i++) {
+          writer.write((i + 1) + ". " + questions.get(i));
+          writer.newLine();
+          if (i < questions.size() - 1) {
+            writer.newLine(); // 题目之间空一行
+          }
         }
+      }
+    } catch (IOException e) {
+      System.out.println("保存试卷时出错：" + e.getMessage());
     }
+  }
 }
\ No newline at end of file
diff --git a/src/PrimaryQuestionGenerator.java b/src/PrimaryQuestionGenerator.java
index a846199..10887e0 100644
--- a/src/PrimaryQuestionGenerator.java
+++ b/src/PrimaryQuestionGenerator.java
@@ -5,37 +5,37 @@ import java.util.Random;
  * 生成适合小学生的数学题目
  */
 public class PrimaryQuestionGenerator implements QuestionGenerator {
-    @Override
-    public String generateQuestion(StringBuilder question, Random random) {
-        int num1 = random.nextInt(100) + 1; // 1-100的随机数
-        int num2 = random.nextInt(100) + 1;
-        String[] operators = {"+", "-", "*", "/"};
-        String op = operators[random.nextInt(operators.length)];
+  @Override
+  public String generateQuestion(StringBuilder question, Random random) {
+    int num1 = random.nextInt(100) + 1; // 1-100的随机数
+    int num2 = random.nextInt(100) + 1;
+    String[] operators = {"+", "-", "*", "/"};
+    String op = operators[random.nextInt(operators.length)];
 
-        // 确保减法和除法结果为正整数
-        if ("-".equals(op) && num1 < num2) {
-            int temp = num1;
-            num1 = num2;
-            num2 = temp;
-        } else if ("/".equals(op)) {
-            // 确保除法结果为整数
-            num1 = num2 * (random.nextInt(10) + 1);
-        }
-
-        // 10%的概率添加括号
-        if (random.nextDouble() < 0.1) {
-            question.append("(");
-            question.append(num1);
-            question.append(" ").append(op).append(" ");
-            question.append(num2);
-            question.append(")");
-        } else {
-            question.append(num1);
-            question.append(" ").append(op).append(" ");
-            question.append(num2);
-        }
+    // 确保减法和除法结果为正整数
+    if ("-".equals(op) && num1 < num2) {
+      int temp = num1;
+      num1 = num2;
+      num2 = temp;
+    } else if ("/".equals(op)) {
+      // 确保除法结果为整数
+      num1 = num2 * (random.nextInt(10) + 1);
+    }
 
-        question.append(" = ?");
-        return question.toString();
+    // 10%的概率添加括号
+    if (random.nextDouble() < 0.1) {
+      question.append("(");
+      question.append(num1);
+      question.append(" ").append(op).append(" ");
+      question.append(num2);
+      question.append(")");
+    } else {
+      question.append(num1);
+      question.append(" ").append(op).append(" ");
+      question.append(num2);
     }
+
+    question.append(" = ?");
+    return question.toString();
+  }
 }
\ No newline at end of file
diff --git a/src/QuestionGenerator.java b/src/QuestionGenerator.java
index 1f99877..31b5906 100644
--- a/src/QuestionGenerator.java
+++ b/src/QuestionGenerator.java
@@ -5,11 +5,11 @@ import java.util.Random;
  * 定义生成数学题目的基本方法
  */
 public interface QuestionGenerator {
-    /**
-     * 生成一道数学题目
-     * @param question 用于构建题目的StringBuilder
-     * @param random 随机数生成器
-     * @return 生成的题目字符串
-     */
-    String generateQuestion(StringBuilder question, Random random);
+  /**
+   * 生成一道数学题目
+   * @param question 用于构建题目的StringBuilder
+   * @param random 随机数生成器
+   * @return 生成的题目字符串
+   */
+  String generateQuestion(StringBuilder question, Random random);
 }
\ No newline at end of file
diff --git a/src/SeniorQuestionGenerator.java b/src/SeniorQuestionGenerator.java
index 465fe65..0444394 100644
--- a/src/SeniorQuestionGenerator.java
+++ b/src/SeniorQuestionGenerator.java
@@ -5,25 +5,25 @@ import java.util.Random;
  * 生成适合高中生的数学题目，包含三角函数运算
  */
 public class SeniorQuestionGenerator implements QuestionGenerator {
-    @Override
-    public String generateQuestion(StringBuilder question, Random random) {
-        // 确保所有高中题目都包含至少一个sin、cos或tan的运算符
-        String[] functions = {"sin(", "cos(", "tan("};
-        String func = functions[random.nextInt(functions.length)];
-        int angle = random.nextInt(100)+1;
+  @Override
+  public String generateQuestion(StringBuilder question, Random random) {
+    // 确保所有高中题目都包含至少一个sin、cos或tan的运算符
+    String[] functions = {"sin(", "cos(", "tan("};
+    String func = functions[random.nextInt(functions.length)];
+    int angle = random.nextInt(100)+1;
 
-        question.append(func).append(angle).append(")");
+    question.append(func).append(angle).append(")");
 
-        // 添加一些其他运算符使题目更复杂
-        int complexity = random.nextInt(3);
-        for (int i = 0; i < complexity; i++) {
-            String[] operators = {"+", "-", "*", "/"};
-            String op = operators[random.nextInt(operators.length)];
-            int num = random.nextInt(10) + 1;
-            question.append(" ").append(op).append(" " ).append(num);
-        }
-
-        question.append(" = ?");
-        return question.toString();
+    // 添加一些其他运算符使题目更复杂
+    int complexity = random.nextInt(3);
+    for (int i = 0; i < complexity; i++) {
+      String[] operators = {"+", "-", "*", "/"};
+      String op = operators[random.nextInt(operators.length)];
+      int num = random.nextInt(10) + 1;
+      question.append(" ").append(op).append(" " ).append(num);
     }
+
+    question.append(" = ?");
+    return question.toString();
+  }
 }
\ No newline at end of file
diff --git a/src/UserInfo.java b/src/UserInfo.java
index 8513036..d85f127 100644
--- a/src/UserInfo.java
+++ b/src/UserInfo.java
@@ -3,51 +3,51 @@
  * 存储用户的基本信息，包括用户名、密码和用户类型
  */
 public class UserInfo {
-    private String username;
-    private String password;
-    private String userType;
+  private String username;
+  private String password;
+  private String userType;
 
-    /**
-     * 构造函数
-     * @param username 用户名
-     * @param password 密码
-     * @param userType 用户类型（小学/初中/高中）
-     */
-    public UserInfo(String username, String password, String userType) {
-        this.username = username;
-        this.password = password;
-        this.userType = userType;
-    }
+  /**
+   * 构造函数
+   * @param username 用户名
+   * @param password 密码
+   * @param userType 用户类型（小学/初中/高中）
+   */
+  public UserInfo(String username, String password, String userType) {
+    this.username = username;
+    this.password = password;
+    this.userType = userType;
+  }
 
-    /**
-     * 获取用户名
-     * @return 用户名
-     */
-    public String getUsername() {
-        return username;
-    }
+  /**
+   * 获取用户名
+   * @return 用户名
+   */
+  public String getUsername() {
+    return username;
+  }
 
-    /**
-     * 获取密码
-     * @return 密码
-     */
-    public String getPassword() {
-        return password;
-    }
+  /**
+   * 获取密码
+   * @return 密码
+   */
+  public String getPassword() {
+    return password;
+  }
 
-    /**
-     * 获取用户类型
-     * @return 用户类型
-     */
-    public String getUserType() {
-        return userType;
-    }
+  /**
+   * 获取用户类型
+   * @return 用户类型
+   */
+  public String getUserType() {
+    return userType;
+  }
 
-    /**
-     * 设置用户类型
-     * @param userType 用户类型
-     */
-    public void setUserType(String userType) {
-        this.userType = userType;
-    }
+  /**
+   * 设置用户类型
+   * @param userType 用户类型
+   */
+  public void setUserType(String userType) {
+    this.userType = userType;
+  }
 }
\ No newline at end of file