diff --git a/src/AbstractMathGenerator.java b/src/AbstractMathGenerator.java
new file mode 100644
index 0000000..d0385ed
--- /dev/null
+++ b/src/AbstractMathGenerator.java
@@ -0,0 +1,37 @@
+import java.util.List;
+
+/**
+ * 数学题目生成器抽象类
+ */
+public abstract class AbstractMathGenerator implements MathGenerator {
+    protected String currentDifficulty;
+    protected String currentUser;
+
+    /**
+     * 验证题目数量范围
+     */
+    protected boolean validateQuestionCount(int count) {
+        return count >= 10 && count <= 30 || count == -1;
+    }
+
+    /**
+     * 验证难度级别
+     */
+    protected boolean validateDifficulty(String difficulty) {
+        return difficulty.equals("小学") || difficulty.equals("初中") || difficulty.equals("高中");
+    }
+
+    /**
+     * 获取当前难度
+     */
+    public String getCurrentDifficulty() {
+        return currentDifficulty;
+    }
+
+    /**
+     * 获取当前用户
+     */
+    public String getCurrentUser() {
+        return currentUser;
+    }
+}
\ No newline at end of file
diff --git a/src/FileService.java b/src/FileService.java
new file mode 100644
index 0000000..6bcf2f3
--- /dev/null
+++ b/src/FileService.java
@@ -0,0 +1,86 @@
+import java.io.*;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.List;
+
+/**
+ * 文件操作服务
+ */
+public class FileService {
+    private final String baseDir;
+
+    public FileService() {
+        this.baseDir = System.getProperty("user.dir") + File.separator + "papers";
+        initializeStorage();
+    }
+
+    /**
+     * 初始化存储目录
+     */
+    private void initializeStorage() {
+        File dir = new File(baseDir);
+        if (!dir.exists()) {
+            dir.mkdirs();
+        }
+    }
+
+    /**
+     * 保存题目到文件
+     */
+    public void saveQuestions(String username, List<String> questions) {
+        String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
+        String filename = timestamp + ".txt";
+        String userDirPath = baseDir + File.separator + username;
+
+        File userDir = new File(userDirPath);
+        if (!userDir.exists()) {
+            userDir.mkdirs();
+        }
+
+        File file = new File(userDir, filename);
+        try (PrintWriter writer = new PrintWriter(new FileWriter(file, true))) {
+            for (int i = 0; i < questions.size(); i++) {
+                writer.println((i + 1) + ". " + questions.get(i));
+                if (i < questions.size() - 1) {
+                    writer.println();
+                }
+            }
+        } catch (IOException e) {
+            System.err.println("保存文件失败: " + e.getMessage());
+        }
+    }
+
+    /**
+     * 加载用户的历史题目用于查重
+     */
+    public void loadHistoryQuestions(String username, java.util.Set<String> questionSet) {
+        File userDir = new File(baseDir + File.separator + username);
+        if (!userDir.exists() || !userDir.isDirectory()) {
+            return;
+        }
+
+        File[] files = userDir.listFiles((dir, name) -> name.endsWith(".txt"));
+        if (files == null) return;
+
+        for (File file : files) {
+            try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
+                String line;
+                while ((line = reader.readLine()) != null) {
+                    if (line.matches("^\\d+\\.\\s+.+")) {
+                        String question = line.substring(line.indexOf(".") + 1).trim();
+                        questionSet.add(normalizeQuestion(question));
+                    }
+                }
+            } catch (IOException e) {
+                System.err.println("读取历史题目失败: " + e.getMessage());
+            }
+        }
+    }
+
+    /**
+     * 规范化题目
+     */
+    private String normalizeQuestion(String question) {
+        return question.replaceAll("\\s+", "").toLowerCase();
+    }
+}
\ No newline at end of file
diff --git a/src/MathGenerator.java b/src/MathGenerator.java
new file mode 100644
index 0000000..f7c617c
--- /dev/null
+++ b/src/MathGenerator.java
@@ -0,0 +1,26 @@
+
+import java.util.List;
+/**
+ * 数学题目生成器接口
+ */
+public interface MathGenerator {
+    /**
+     * 生成指定数量的题目
+     */
+    List<String> generateQuestions(int count);
+
+    /**
+     * 切换难度级别
+     */
+    void switchDifficulty(String level);
+
+    /**
+     * 用户登录
+     */
+    boolean login(String username, String password);
+
+    /**
+     * 保存题目到文件
+     */
+    void saveToFile(List<String> questions);
+}
\ No newline at end of file
diff --git a/src/MathTestGenerator.java b/src/MathTestGenerator.java
index d5d4832..ad7a0c5 100644
--- a/src/MathTestGenerator.java
+++ b/src/MathTestGenerator.java
@@ -1,107 +1,93 @@
-import java.io.*;
-import java.text.SimpleDateFormat;
+import entities.User;
+import entities.UserType;
 import java.util.*;
 
 /**
- * 中小学数学卷子自动生成程序
+ * 中小学数学卷子自动生成程序 - 主类
  * 作者：张三
  * 班级：软1班
  */
-public class MathTestGenerator {
-
-    private static final Map<String, User> USERS = new HashMap<>();
-    static {
-        // 小学账户
-        USERS.put("张三1", new User("张三1", "123", UserType.PRIMARY));
-        USERS.put("张三2", new User("张三2", "123", UserType.PRIMARY));
-        USERS.put("张三3", new User("张三3", "123", UserType.PRIMARY));
-        // 初中账户
-        USERS.put("李四1", new User("李四1", "123", UserType.JUNIOR));
-        USERS.put("李四2", new User("李四2", "123", UserType.JUNIOR));
-        USERS.put("李四3", new User("李四3", "123", UserType.JUNIOR));
-        // 高中账户
-        USERS.put("王五1", new User("王五1", "123", UserType.SENIOR));
-        USERS.put("王五2", new User("王五2", "123", UserType.SENIOR));
-        USERS.put("王五3", new User("王五3", "123", UserType.SENIOR));
-    }
+public class MathTestGenerator extends AbstractMathGenerator {
+    private final UserService userService;
+    private final QuestionService questionService;
+    private final FileService fileService;
+    private final ValidationService validationService;
+    private final Scanner scanner;
 
-    // 用户类型枚举
-    private enum UserType {
-        PRIMARY("小学"), JUNIOR("初中"), SENIOR("高中");
+    private User currentUser;
 
-        private final String name;
-        UserType(String name) { this.name = name; }
-        public String getName() { return name; }
+    public MathTestGenerator() {
+        this.userService = new UserService();
+        this.questionService = new QuestionService();
+        this.fileService = new FileService();
+        this.validationService = new ValidationService();
+        this.scanner = new Scanner(System.in);
     }
 
-    // 用户类
-    private static class User {
-        String username;
-        String password;
-        UserType type;
+    @Override
+    public boolean login(String username, String password) {
+        User user = userService.authenticate(username, password);
+        if (user != null) {
+            this.currentUser = user;
+            this.currentDifficulty = user.getType().getName();
+
+            System.out.println("当前选择为" + currentDifficulty + "出题");
 
-        User(String username, String password, UserType type) {
-            this.username = username;
-            this.password = password;
-            this.type = type;
+            // 加载历史题目用于查重
+            Set<String> historyQuestions = new HashSet<>();
+            fileService.loadHistoryQuestions(username, historyQuestions);
+            // 这里需要将历史题目传递给questionService
+            return true;
         }
+        return false;
     }
 
-    // 运算符枚举
-    private enum Operator {
-        ADD("+", 1), SUBTRACT("-", 1), MULTIPLY("*", 2), DIVIDE("/", 2),
-        POWER("^", 3), SQRT("√", 3), SIN("sin", 4), COS("cos", 4), TAN("tan", 4);
+    @Override
+    public List<String> generateQuestions(int count) {
+        if (currentUser == null) {
+            throw new IllegalStateException("请先登录");
+        }
+
+        questionService.setCurrentType(UserType.fromName(currentDifficulty));
+        List<String> questions = new ArrayList<>();
 
-        private final String symbol;
-        private final int priority;
-        Operator(String symbol, int priority) {
-            this.symbol = symbol;
-            this.priority = priority;
+        for (int i = 0; i < count; i++) {
+            questions.add(questionService.generateQuestion());
         }
-        public String getSymbol() { return symbol; }
-        public int getPriority() { return priority; }
+
+        return questions;
     }
 
-    private User currentUser;
-    private UserType currentType;
-    private Set<String> generatedQuestions;
-    private Scanner scanner;
-    private String baseDir;
+    @Override
+    public void switchDifficulty(String level) {
 
-    public MathTestGenerator() {
-        this.scanner = new Scanner(System.in);
-        this.generatedQuestions = new HashSet<>();
-        this.baseDir = System.getProperty("user.dir") + File.separator + "papers";
-        initializeStorage();
+        this.currentDifficulty = level;
+        System.out.println("准备生成" + level + "数学题目，请输入生成题目数量");
     }
 
-    /**
-     * 初始化存储目录
-     */
-    private void initializeStorage() {
-        File dir = new File(baseDir);
-        if (!dir.exists()) {
-            dir.mkdirs();
-        }
+    @Override
+    public void saveToFile(List<String> questions) {
+        fileService.saveQuestions(currentUser.getUsername(), questions);
     }
 
     /**
-     * 主程序入口
+     * 启动程序
      */
     public void start() {
         System.out.println("=== 中小学数学卷子自动生成程序 ===");
 
         while (true) {
-            if (login()) {
+            if (performLogin()) {
+
                 generatePapers();
             }
         }
     }
 
     /**
-     * 用户登录
+     * 执行登录流程
      */
-    private boolean login() {
+    private boolean performLogin() {
         while (true) {
             System.out.print("请输入用户名和密码（用空格隔开，输入exit退出程序）：");
             String input = scanner.nextLine().trim();
@@ -110,21 +96,16 @@ public class MathTestGenerator {
                 System.exit(0);
             }
 
-            String[] credentials = input.split("\\s+");
-            if (credentials.length != 2) {
+            if (!validationService.isValidCredentialsFormat(input)) {
                 System.out.println("请输入正确的用户名、密码");
                 continue;
             }
 
+            String[] credentials = input.split("\\s+");
             String username = credentials[0];
             String password = credentials[1];
 
-            User user = USERS.get(username);
-            if (user != null && user.password.equals(password)) {
-                currentUser = user;
-                currentType = user.type;
-                System.out.println("当前选择为" + currentType.getName() + "出题");
-                loadGeneratedQuestions();
+            if (login(username, password)) {
                 return true;
             } else {
                 System.out.println("请输入正确的用户名、密码");
@@ -133,261 +114,67 @@ public class MathTestGenerator {
     }
 
     /**
-     * 加载已生成的题目用于查重
-     */
-    private void loadGeneratedQuestions() {
-        generatedQuestions.clear();
-        File userDir = new File(baseDir + File.separator + currentUser.username);
-        if (userDir.exists() && userDir.isDirectory()) {
-            File[] files = userDir.listFiles((dir, name) -> name.endsWith(".txt"));
-            if (files != null) {
-                for (File file : files) {
-                    try (BufferedReader reader = new BufferedReader(new FileReader(file))) {
-                        String line;
-                        while ((line = reader.readLine()) != null) {
-                            if (line.matches("^\\d+\\.\\s+.+")) {
-                                String question = line.substring(line.indexOf(".") + 1).trim();
-                                generatedQuestions.add(normalizeQuestion(question));
-                            }
-                        }
-                    } catch (IOException e) {
-                        System.out.println("读取历史题目失败: " + e.getMessage());
-                    }
-                }
-            }
-        }
-    }
-
-    /**
-     * 生成试卷
+     * 生成试卷流程
      */
     private void generatePapers() {
         while (true) {
-            System.out.print("准备生成" + currentType.getName() +
+            System.out.print("准备生成" + currentDifficulty +
                     "数学题目，请输入生成题目数量（10-30，输入-1退出当前用户）：");
 
             String input = scanner.nextLine().trim();
 
             if (input.equals("-1")) {
                 currentUser = null;
-                currentType = null;
+                currentDifficulty = null;
+                questionService.clearGeneratedQuestions();
                 System.out.println("已退出当前用户，请重新登录");
                 return;
             }
 
-            if (isSwitchCommand(input)) {
+            if (validationService.isValidSwitchCommand(input)) {
+
                 handleSwitchCommand(input);
                 continue;
             }
 
+            if (!validationService.isValidQuestionCount(input)) {
+                System.out.println("题目数量应在10-30之间");
+                continue;
+            }
+
             try {
                 int count = Integer.parseInt(input);
-                if (count >= 10 && count <= 30) {
-                    generateTestPaper(count);
-                } else {
-                    System.out.println("题目数量应在10-30之间");
-                }
-            } catch (NumberFormatException e) {
-                System.out.println("请输入有效的数字");
+                List<String> questions = generateQuestions(count);
+                saveToFile(questions);
+                System.out.println("试卷生成成功！生成题目数量：" + questions.size());
+            } catch (Exception e) {
+                System.out.println("生成题目失败: " + e.getMessage());
             }
         }
     }
 
-    /**
-     * 检查是否为切换命令
-     */
-    private boolean isSwitchCommand(String input) {
-        return input.startsWith("切换为");
-    }
-
     /**
      * 处理切换命令
      */
     private void handleSwitchCommand(String input) {
-        String typeStr = input.substring(3).trim();
-        try {
-            UserType newType = UserType.valueOf(typeStr.toUpperCase());
-            currentType = newType;
-            System.out.println("准备生成" + currentType.getName() + "数学题目，请输入生成题目数量");
-        } catch (IllegalArgumentException e) {
-            System.out.println("请输入小学、初中和高中三个选项中的一个");
-        }
-    }
+        String level = validationService.extractDifficulty(input);
+        while(!level.equals("小学")&&!level.equals("初中")&&!level.equals("高中")) {
+            System.out.print("请输入小学、初中和高中三个选项中的一个\n");
+            Scanner sc = new Scanner(System.in);
 
-    /**
-     * 生成试卷文件
-     */
-    private void generateTestPaper(int questionCount) {
-        List<String> questions = new ArrayList<>();
-        int generated = 0;
-        int attempts = 0;
-        final int MAX_ATTEMPTS = 1000;
-
-        while (generated < questionCount && attempts < MAX_ATTEMPTS) {
-            String question = generateQuestion();
-            String normalized = normalizeQuestion(question);
-
-            if (!generatedQuestions.contains(normalized)) {
-                questions.add(question);
-                generatedQuestions.add(normalized);
-                generated++;
-            }
-            attempts++;
-        }
+            level = validationService.extractDifficulty(sc.nextLine().trim());
 
-        if (generated < questionCount) {
-            System.out.println("警告：无法生成足够的不重复题目，已生成 " + generated + " 道题");
         }
-
-        saveToFile(questions);
-        System.out.println("试卷生成成功！");
-    }
-
-    /**
-     * 生成单个题目
-     */
-    private String generateQuestion() {
-        Random random = new Random();
-        int operandCount = random.nextInt(5) + 1; // 1-5个操作数
-        StringBuilder question = new StringBuilder();
-        List<Integer> operands = new ArrayList<>();
-        List<Operator> operators = new ArrayList<>();
-
-        // 生成操作数
-        for (int i = 0; i < operandCount; i++) {
-            operands.add(random.nextInt(100) + 1);
-        }
-
-        // 根据难度生成运算符
-        switch (currentType) {
-            case PRIMARY:
-                generatePrimaryOperators(operators, operandCount - 1, random);
-                break;
-            case JUNIOR:
-                generateJuniorOperators(operators, operandCount - 1, random);
-                break;
-            case SENIOR:
-                generateSeniorOperators(operators, operandCount - 1, random);
-                break;
-        }
-
-        // 构建题目表达式
-        question.append(operands.get(0));
-        for (int i = 0; i < operators.size(); i++) {
-            Operator op = operators.get(i);
-            if (op == Operator.SQRT) {
-                question.insert(0, "√(").append(")");
-                question.append(op.getSymbol()).append(operands.get(i + 1));
-            } else if (op == Operator.SIN || op == Operator.COS || op == Operator.TAN) {
-                question.append(op.getSymbol()).append("(").append(operands.get(i + 1)).append(")");
-            } else {
-                question.append(" ").append(op.getSymbol()).append(" ").append(operands.get(i + 1));
-            }
-        }
-
-        // 随机添加括号
-        if (operandCount > 2 && random.nextBoolean()) {
-            question.insert(0, "(");
-            int insertPos = question.indexOf(" ", question.indexOf(" ") + 1);
-            if (insertPos != -1) {
-                question.insert(insertPos + 1, ")");
-            }
-        }
-
-        return question.toString();
-    }
-
-    /**
-     * 生成小学运算符
-     */
-    private void generatePrimaryOperators(List<Operator> operators, int count, Random random) {
-        Operator[] primaryOps = {Operator.ADD, Operator.SUBTRACT, Operator.MULTIPLY, Operator.DIVIDE};
-        for (int i = 0; i < count; i++) {
-            operators.add(primaryOps[random.nextInt(primaryOps.length)]);
-        }
-    }
-
-    /**
-     * 生成初中运算符（必须包含平方或开根号）
-     */
-    private void generateJuniorOperators(List<Operator> operators, int count, Random random) {
-        Operator[] juniorOps = {Operator.ADD, Operator.SUBTRACT, Operator.MULTIPLY, Operator.DIVIDE,
-                Operator.POWER, Operator.SQRT};
-
-        // 确保至少有一个平方或开根号
-        boolean hasSpecialOp = false;
-        for (int i = 0; i < count; i++) {
-            Operator op = juniorOps[random.nextInt(juniorOps.length)];
-            if (op == Operator.POWER || op == Operator.SQRT) {
-                hasSpecialOp = true;
-            }
-            operators.add(op);
-        }
-
-        if (!hasSpecialOp && count > 0) {
-            operators.set(random.nextInt(count),
-                    random.nextBoolean() ? Operator.POWER : Operator.SQRT);
-        }
-    }
-
-    /**
-     * 生成高中运算符（必须包含三角函数）
-     */
-    private void generateSeniorOperators(List<Operator> operators, int count, Random random) {
-        Operator[] seniorOps = {Operator.ADD, Operator.SUBTRACT, Operator.MULTIPLY, Operator.DIVIDE,
-                Operator.POWER, Operator.SQRT, Operator.SIN, Operator.COS, Operator.TAN};
-
-        // 确保至少有一个三角函数
-        boolean hasTrigOp = false;
-        for (int i = 0; i < count; i++) {
-            Operator op = seniorOps[random.nextInt(seniorOps.length)];
-            if (op == Operator.SIN || op == Operator.COS || op == Operator.TAN) {
-                hasTrigOp = true;
+            try {
+                switchDifficulty(level);
+            } catch (IllegalArgumentException e) {
+                System.out.println(e.getMessage());
             }
-            operators.add(op);
-        }
 
-        if (!hasTrigOp && count > 0) {
-            Operator[] trigOps = {Operator.SIN, Operator.COS, Operator.TAN};
-            operators.set(random.nextInt(count), trigOps[random.nextInt(trigOps.length)]);
-        }
-    }
 
-    /**
-     * 规范化题目用于查重
-     */
-    private String normalizeQuestion(String question) {
-        return question.replaceAll("\\s+", "").toLowerCase();
-    }
 
-    /**
-     * 保存题目到文件
-     */
-    private void saveToFile(List<String> questions) {
-        String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
-        String filename = timestamp + ".txt";
-        String userDirPath = baseDir + File.separator + currentUser.username;
-
-        File userDir = new File(userDirPath);
-        if (!userDir.exists()) {
-            userDir.mkdirs();
-        }
-
-        File file = new File(userDir, filename);
-        try (PrintWriter writer = new PrintWriter(new FileWriter(file))) {
-            for (int i = 0; i < questions.size(); i++) {
-                writer.println((i + 1) + ". " + questions.get(i));
-                if (i < questions.size() - 1) {
-                    writer.println();
-                }
-            }
-        } catch (IOException e) {
-            System.out.println("保存文件失败: " + e.getMessage());
-        }
     }
 
-
-
     /**
      * 主方法
      */
diff --git a/src/Operator.java b/src/Operator.java
new file mode 100644
index 0000000..41a1e24
--- /dev/null
+++ b/src/Operator.java
@@ -0,0 +1,32 @@
+package entities;
+
+/**
+ * 运算符枚举
+ */
+public enum Operator {
+    ADD("+", 1, "小学初中高中"),
+    SUBTRACT("-", 1, "小学初中高中"),
+    MULTIPLY("*", 2, "小学初中高中"),
+    DIVIDE("/", 2, "小学初中高中"),
+    POWER("^", 3, "初中高中"),
+    SQRT("√", 3, "初中高中"),
+    SIN("sin", 4, "高中"),
+    COS("cos", 4, "高中"),
+    TAN("tan", 4, "高中");
+
+    private final String symbol;
+    private final int priority;
+    private final String allowedLevels;
+
+    Operator(String symbol, int priority, String allowedLevels) {
+        this.symbol = symbol;
+        this.priority = priority;
+        this.allowedLevels = allowedLevels;
+    }
+
+    public String getSymbol() { return symbol; }
+    public int getPriority() { return priority; }
+    public boolean isAllowedForLevel(String level) {
+        return allowedLevels.contains(level);
+    }
+}
\ No newline at end of file
diff --git a/src/QuestionService.java b/src/QuestionService.java
new file mode 100644
index 0000000..2d1261a
--- /dev/null
+++ b/src/QuestionService.java
@@ -0,0 +1,192 @@
+import entities.Operator;
+import entities.UserType;
+import java.util.*;
+
+/**
+ * 题目生成服务
+ */
+public class QuestionService {
+    private final Random random;
+    private final Set<String> generatedQuestions;
+    private UserType currentType;
+
+    public QuestionService() {
+        this.random = new Random();
+        this.generatedQuestions = new HashSet<>();
+    }
+
+    /**
+     * 设置当前题目类型
+     */
+    public void setCurrentType(UserType type) {
+        this.currentType = type;
+    }
+
+    /**
+     * 生成单个题目
+     */
+    public String generateQuestion() {
+        String question;
+        int attempts = 0;
+
+        do {
+            question = generateUniqueQuestion();
+            attempts++;
+        } while (generatedQuestions.contains(normalizeQuestion(question)) && attempts < 100);
+
+        generatedQuestions.add(normalizeQuestion(question));
+        return question;
+    }
+
+    /**
+     * 生成唯一题目
+     */
+    private String generateUniqueQuestion() {
+        int operandCount = random.nextInt(5) + 1;
+        List<Integer> operands = generateOperands(operandCount);
+        List<Operator> operators = generateOperators(operandCount - 1);
+
+        return buildExpression(operands, operators);
+    }
+
+    /**
+     * 生成操作数
+     */
+    private List<Integer> generateOperands(int count) {
+        List<Integer> operands = new ArrayList<>();
+        for (int i = 0; i < count; i++) {
+            operands.add(random.nextInt(100) + 1);
+        }
+        return operands;
+    }
+
+    /**
+     * 生成运算符
+     */
+    private List<Operator> generateOperators(int count) {
+        List<Operator> operators = new ArrayList<>();
+        List<Operator> allowedOperators = getAllowedOperators();
+
+        // 确保符合难度要求
+        if (currentType == UserType.JUNIOR) {
+            ensureJuniorRequirement(operators, allowedOperators, count);
+        } else if (currentType == UserType.SENIOR) {
+            ensureSeniorRequirement(operators, allowedOperators, count);
+        } else {
+            for (int i = 0; i < count; i++) {
+                operators.add(allowedOperators.get(random.nextInt(allowedOperators.size())));
+            }
+        }
+
+        return operators;
+    }
+
+    /**
+     * 获取允许的运算符
+     */
+    private List<Operator> getAllowedOperators() {
+        List<Operator> allowed = new ArrayList<>();
+        String level = currentType.getName();
+
+        for (Operator op : Operator.values()) {
+            if (op.isAllowedForLevel(level)) {
+                allowed.add(op);
+            }
+        }
+        return allowed;
+    }
+
+    /**
+     * 确保初中题目要求（包含平方或开根号）
+     */
+    private void ensureJuniorRequirement(List<Operator> operators, List<Operator> allowed, int count) {
+        boolean hasSpecialOp = false;
+
+        for (int i = 0; i < count; i++) {
+            Operator op = allowed.get(random.nextInt(allowed.size()));
+            operators.add(op);
+            if (op == Operator.POWER || op == Operator.SQRT) {
+                hasSpecialOp = true;
+            }
+        }
+
+        if (!hasSpecialOp && count > 0) {
+            int index = random.nextInt(operators.size());
+            operators.set(index, random.nextBoolean() ? Operator.POWER : Operator.SQRT);
+        }
+    }
+
+    /**
+     * 确保高中题目要求（包含三角函数）
+     */
+    private void ensureSeniorRequirement(List<Operator> operators, List<Operator> allowed, int count) {
+        boolean hasTrigOp = false;
+
+        for (int i = 0; i < count; i++) {
+            Operator op = allowed.get(random.nextInt(allowed.size()));
+            operators.add(op);
+            if (op == Operator.SIN || op == Operator.COS || op == Operator.TAN) {
+                hasTrigOp = true;
+            }
+        }
+
+        if (!hasTrigOp && count > 0) {
+            int index = random.nextInt(operators.size());
+            Operator[] trigOps = {Operator.SIN, Operator.COS, Operator.TAN};
+            operators.set(index, trigOps[random.nextInt(trigOps.length)]);
+        }
+    }
+
+    /**
+     * 构建表达式
+     */
+    private String buildExpression(List<Integer> operands, List<Operator> operators) {
+        StringBuilder expression = new StringBuilder();
+
+        expression.append(operands.get(0));
+
+        for (int i = 0; i < operators.size(); i++) {
+            Operator op = operators.get(i);
+            int operand = operands.get(i + 1);
+
+            switch (op) {
+                case SQRT:
+                    expression.insert(0, "√(").append(")");
+                    expression.append(op.getSymbol()).append(operand);
+                    break;
+                case SIN:
+                case COS:
+                case TAN:
+                    expression.append(op.getSymbol()).append("(").append(operand).append(")");
+                    break;
+                default:
+                    expression.append(" ").append(op.getSymbol()).append(" ").append(operand);
+            }
+        }
+
+        // 随机添加括号
+        if (operands.size() > 2 && random.nextBoolean()) {
+            expression.insert(0, "(");
+            int spaceIndex = expression.indexOf(" ", expression.indexOf(" ") + 1);
+            if (spaceIndex != -1) {
+                expression.insert(spaceIndex + 1, ")");
+            }
+        }
+
+        return expression.toString();
+    }
+
+    /**
+     * 规范化题目用于查重
+     */
+    private String normalizeQuestion(String question) {
+        return question.replaceAll("\\s+", "").toLowerCase();
+    }
+
+    /**
+     * 清空已生成题目记录（用户退出时）
+     */
+    public void clearGeneratedQuestions() {
+        generatedQuestions.clear();
+    }
+}
\ No newline at end of file
diff --git a/src/User.java b/src/User.java
new file mode 100644
index 0000000..79b1467
--- /dev/null
+++ b/src/User.java
@@ -0,0 +1,21 @@
+package entities;
+
+/**
+ * 用户实体类
+ */
+public class User {
+    private String username;
+    private String password;
+    private UserType type;
+
+    public User(String username, String password, UserType type) {
+        this.username = username;
+        this.password = password;
+        this.type = type;
+    }
+
+    // Getter方法
+    public String getUsername() { return username; }
+    public String getPassword() { return password; }
+    public UserType getType() { return type; }
+}    
\ No newline at end of file
diff --git a/src/UserService.java b/src/UserService.java
new file mode 100644
index 0000000..92085fd
--- /dev/null
+++ b/src/UserService.java
@@ -0,0 +1,54 @@
+import entities.User;
+import entities.UserType;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * 用户管理服务
+ */
+public class UserService {
+    private final Map<String, User> users;
+
+    public UserService() {
+        this.users = new HashMap<>();
+        initializeUsers();
+    }
+
+    /**
+     * 初始化用户数据
+     */
+    private void initializeUsers() {
+        // 小学账户
+        users.put("张三1", new User("张三1", "123", UserType.PRIMARY));
+        users.put("张三2", new User("张三2", "123", UserType.PRIMARY));
+        users.put("张三3", new User("张三3", "123", UserType.PRIMARY));
+
+        // 初中账户
+        users.put("李四1", new User("李四1", "123", UserType.JUNIOR));
+        users.put("李四2", new User("李四2", "123", UserType.JUNIOR));
+        users.put("李四3", new User("李四3", "123", UserType.JUNIOR));
+
+        // 高中账户
+        users.put("王五1", new User("王五1", "123", UserType.SENIOR));
+        users.put("王五2", new User("王五2", "123", UserType.SENIOR));
+        users.put("王五3", new User("王五3", "123", UserType.SENIOR));
+    }
+
+    /**
+     * 用户认证
+     */
+    public User authenticate(String username, String password) {
+        User user = users.get(username);
+        if (user != null && user.getPassword().equals(password)) {
+            return user;
+        }
+        return null;
+    }
+
+    /**
+     * 获取所有用户（用于测试）
+     */
+    public Map<String, User> getUsers() {
+        return new HashMap<>(users);
+    }
+}
\ No newline at end of file
diff --git a/src/UserType.java b/src/UserType.java
new file mode 100644
index 0000000..8317ac5
--- /dev/null
+++ b/src/UserType.java
@@ -0,0 +1,32 @@
+package entities;
+
+/**
+ * 用户类型枚举
+ */
+public enum UserType {
+    PRIMARY("小学"),
+    JUNIOR("初中"),
+    SENIOR("高中");
+
+    private final String name;
+
+    UserType(String name) {
+        this.name = name;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * 根据中文名称获取枚举值
+     */
+    public static UserType fromName(String name) {
+        for (UserType type : values()) {
+            if (type.name.equals(name)) {
+                return type;
+            }
+        }
+        throw new IllegalArgumentException("无效的用户类型: " + name);
+    }
+}
\ No newline at end of file
diff --git a/src/ValidationService.java b/src/ValidationService.java
new file mode 100644
index 0000000..9c1a409
--- /dev/null
+++ b/src/ValidationService.java
@@ -0,0 +1,49 @@
+import java.util.regex.Pattern;
+
+/**
+ * 输入验证服务
+ */
+public class ValidationService {
+
+    /**
+     * 验证切换命令格式
+     */
+    public boolean isValidSwitchCommand(String input) {
+        if (!input.startsWith("切换为")) {
+            return false;
+        }
+
+       return true;
+    }
+
+    /**
+     * 验证题目数量
+     */
+    public boolean isValidQuestionCount(String input) {
+        if (input.equals("-1")) {
+            return true;
+        }
+
+        try {
+            int count = Integer.parseInt(input);
+            return count >= 10 && count <= 30;
+        } catch (NumberFormatException e) {
+            return false;
+        }
+    }
+
+    /**
+     * 验证用户名密码格式
+     */
+    public boolean isValidCredentialsFormat(String input) {
+        String[] parts = input.split("\\s+");
+        return parts.length == 2;
+    }
+
+    /**
+     * 提取难度级别
+     */
+    public String extractDifficulty(String switchCommand) {
+        return switchCommand.substring(3).trim();
+    }
+}
\ No newline at end of file