diff --git a/README.md b/README.md
deleted file mode 100644
index 8a4459c..0000000
--- a/README.md
+++ /dev/null
@@ -1,2 +0,0 @@
-# partner_project
-
diff --git a/src/auth/User.java b/src/auth/User.java
new file mode 100644
index 0000000..fdb6079
--- /dev/null
+++ b/src/auth/User.java
@@ -0,0 +1,20 @@
+package auth;
+
+public class User {
+    private String username;
+    private String password;
+    private String type;
+    private String email;
+
+    public User(String username, String password, String type, String email) {
+        this.username = username;
+        this.password = password;
+        this.type = type;
+        this.email = email;
+    }
+
+    public String getUsername() { return username; }
+    public String getPassword() { return password; }
+    public String getType() { return type; }
+    public String getEmail() { return email; }
+}
diff --git a/src/auth/UserManager.java b/src/auth/UserManager.java
new file mode 100644
index 0000000..f2efced
--- /dev/null
+++ b/src/auth/UserManager.java
@@ -0,0 +1,13 @@
+package auth;
+
+public class UserManager {
+    private final AuthService authService;
+
+    public UserManager() {
+        this.authService = new AuthService();
+    }
+
+    public User login(String username, String password) {
+        return authService.login(username, password);
+    }
+}
diff --git a/src/generator/HighGenerator.java b/src/generator/HighGenerator.java
new file mode 100644
index 0000000..905edf1
--- /dev/null
+++ b/src/generator/HighGenerator.java
@@ -0,0 +1,28 @@
+package generator;
+
+import util.ExpressionUtils;
+import java.util.*;
+
+public class HighGenerator implements ProblemGenerator {
+    @Override
+    public List<Problem> generateProblems(int count) {
+        List<Problem> problems = new ArrayList<>();
+        int attempts = 0;
+        final int maxAttempts = count * 3; // 最多尝试3倍数量
+        
+        while (problems.size() < count && attempts < maxAttempts) {
+            Problem problem = ExpressionUtils.generateHighExpr();
+            if (problem != null) {
+                problems.add(problem);
+            }
+            attempts++;
+        }
+        
+        // 如果无法生成足够题目，用简单题目填充
+        while (problems.size() < count) {
+            problems.add(ExpressionUtils.createProblem("sin(30) + " + (problems.size() + 1)));
+        }
+        
+        return problems;
+    }
+}
\ No newline at end of file
diff --git a/src/generator/MiddleGenerator.java b/src/generator/MiddleGenerator.java
new file mode 100644
index 0000000..1815304
--- /dev/null
+++ b/src/generator/MiddleGenerator.java
@@ -0,0 +1,15 @@
+package generator;
+
+import util.ExpressionUtils;
+import java.util.*;
+
+public class MiddleGenerator implements ProblemGenerator {
+    @Override
+    public List<Problem> generateProblems(int count) {
+        List<Problem> problems = new ArrayList<>();
+        for (int i = 0; i < count; i++) {
+            problems.add(ExpressionUtils.generateMiddleExpr());
+        }
+        return problems;
+    }
+}
\ No newline at end of file
diff --git a/src/generator/PrimaryGenerator.java b/src/generator/PrimaryGenerator.java
new file mode 100644
index 0000000..4609a5a
--- /dev/null
+++ b/src/generator/PrimaryGenerator.java
@@ -0,0 +1,15 @@
+package generator;
+
+import util.ExpressionUtils;
+import java.util.*;
+
+public class PrimaryGenerator implements ProblemGenerator {
+    @Override
+    public List<Problem> generateProblems(int count) {
+        List<Problem> problems = new ArrayList<>(count);
+        for (int i = 0; i < count; i++) {
+            problems.add( ExpressionUtils.generatePrimaryExpr());
+        }
+        return problems;
+    }
+}
\ No newline at end of file
diff --git a/src/generator/Problem.java b/src/generator/Problem.java
new file mode 100644
index 0000000..bbf5127
--- /dev/null
+++ b/src/generator/Problem.java
@@ -0,0 +1,61 @@
+package generator;
+
+import java.util.List;
+import java.util.Collections;
+
+public class Problem {
+    private final String expression;
+    private final double result;
+    private final List<String> options;
+    private final String correctAnswerOption;
+
+    public Problem(String expression, double result, List<String> options,
+                   String correctAnswerOption) {
+        this.expression = expression;
+        this.result = result;
+        this.options = options;
+        this.correctAnswerOption = correctAnswerOption;
+    }
+
+    public String getQuestionText() {
+        return "计算: " + expression + " = ?";
+    }
+
+    public String getExpression() {
+        return expression;
+    }
+
+    public List<String> getOptions() {
+        return Collections.unmodifiableList(options);
+    }
+
+    public String getCorrectAnswerOption() {
+        return formatResult(result);
+    }
+    
+    private String formatResult(double result) {
+        if (Double.isNaN(result)) {
+            return "Error";
+        }
+        if (Math.abs(result - Math.round(result)) < 0.0001) {
+            return String.valueOf((int) Math.round(result));
+        }
+        return String.format("%.2f", result);
+    }
+
+    public double getResult() {
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(getQuestionText()).append("\n");
+        char optionChar = 'A';
+        for (String option : options) {
+            sb.append(optionChar++).append(". ").append(option).append("  ");
+        }
+        sb.append("\n正确答案: ").append(correctAnswerOption);
+        return sb.toString();
+    }
+}
\ No newline at end of file
diff --git a/src/generator/ProblemGenerator.java b/src/generator/ProblemGenerator.java
new file mode 100644
index 0000000..d9a821e
--- /dev/null
+++ b/src/generator/ProblemGenerator.java
@@ -0,0 +1,7 @@
+package generator;
+
+import java.util.List;
+
+public interface ProblemGenerator {
+    List<Problem> generateProblems(int count);
+}
diff --git a/src/service/ExamService.java b/src/service/ExamService.java
new file mode 100644
index 0000000..ff1e339
--- /dev/null
+++ b/src/service/ExamService.java
@@ -0,0 +1,109 @@
+package service;
+
+import auth.User;
+import generator.Problem;
+import generator.ProblemGenerator;
+import generator.PrimaryGenerator;
+import generator.MiddleGenerator;
+import generator.HighGenerator;
+import util.FileUtils;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+
+public class ExamService {
+
+    public ProblemGenerator getGenerator(String type) {
+        switch (type) {
+            case "小学": return new PrimaryGenerator();
+            case "初中": return new MiddleGenerator();
+            case "高中": return new HighGenerator();
+            default: return null;
+        }
+    }
+
+    private Problem generateUniqueProblem(ProblemGenerator generator,
+                                          Set<String> historyExpressions) {
+        int attempts = 0;
+        final int maxAttemptsPerProblem = 1000;
+
+        while (attempts < maxAttemptsPerProblem) {
+            Problem problem = generator.generateProblems(1).get(0);
+            // 查重基于题干 (表达式字符串)
+            if (!historyExpressions.contains(problem.getExpression())) {
+                historyExpressions.add(problem.getExpression());
+                return problem;
+            }
+            attempts++;
+        }
+        return null;
+    }
+
+    // R5: 生成一张唯一试卷，并将其保存到用户的历史记录中。
+    public List<Problem> generateExam(User currentUser, int count) {
+        if (count < 10 || count > 30) {
+            throw new IllegalArgumentException("题目数量必须在 10 到 30 之间");
+        }
+
+        ProblemGenerator generator = getGenerator(currentUser.getType());
+        if (generator == null) {
+            System.err.println("错误: 无法获取题目生成器，用户类型: " + currentUser.getType());
+            return new ArrayList<>();
+        }
+        
+        Set<String> historyExpressions = FileUtils.loadHistory(currentUser.getUsername());
+        List<Problem> problems = new ArrayList<>();
+
+        for(int i = 0; i < count; i++) {
+            Problem problem = generateUniqueProblem(generator, historyExpressions);
+            if (problem != null) {
+                problems.add(problem);
+            } else {
+                System.err.println("警告: 无法生成足够数量的唯一题目。已生成: " + problems.size() + " 题");
+                break;
+            }
+        }
+
+        if (!problems.isEmpty()) {
+            FileUtils.saveProblems(currentUser.getUsername(), problems);
+        } else {
+            System.err.println("错误: 未能生成任何题目");
+        }
+        
+        return problems;
+    }
+
+    // 将这个私有方法改为公共方法，以便在其他类中调用
+    public boolean isAnswerCorrect(Problem problem, String userAnswer) {
+        if (userAnswer == null || problem.getCorrectAnswerOption() == null) {
+            return false;
+        }
+        
+        boolean isCorrect = userAnswer.trim().equalsIgnoreCase(problem.getCorrectAnswerOption().trim());
+        return isCorrect;
+    }
+
+    // R6: 根据答对的百分比计算分数。
+    public int calculateScore(List<Problem> problems, List<String> answers) {
+        if (problems == null || answers == null || 
+            problems.size() != answers.size() || 
+            problems.isEmpty()) {
+            System.err.println("评分错误: 题目和答案数量不匹配");
+            return 0;
+        }
+
+        int correctCount = 0;
+        for (int i = 0; i < problems.size(); i++) {
+            Problem problem = problems.get(i);
+            String userAnswer = answers.get(i);
+            
+            if (isAnswerCorrect(problem, userAnswer)) {
+                correctCount++;
+            }
+        }
+
+        double score = ((double) correctCount / problems.size()) * 100;
+        int finalScore = (int) Math.round(score);
+        return finalScore;
+    }
+}
\ No newline at end of file
diff --git a/src/util/EmailService.java b/src/util/EmailService.java
new file mode 100644
index 0000000..1535aab
--- /dev/null
+++ b/src/util/EmailService.java
@@ -0,0 +1,69 @@
+package util;
+
+import java.util.Properties;
+import java.util.Random;
+import javax.mail.*;
+import javax.mail.internet.InternetAddress;
+import javax.mail.internet.MimeMessage;
+
+public class EmailService {
+    // 邮件配置：请修改此处或设置环境变量
+    private static final String SENDER_EMAIL = "2810672597@qq.com";
+    private static final String SENDER_PASSWORD =("acyhhpwgcqkqdgff");
+    private static final String SMTP_HOST = "smtp.qq.com"; // 例如: smtp.gmail.com
+    private static final String SMTP_PORT = "587"; // 或 465 (SSL)
+    private static final String SUBJECT = "数学学习软件注册验证码";
+
+    public String generateVerificationCode() {
+        Random rand = new Random();
+        return String.format("%06d", rand.nextInt(1000000));
+    }
+
+    private Properties getMailProperties() {
+        Properties props = new Properties();
+        props.put("mail.smtp.auth", "true");
+        props.put("mail.smtp.starttls.enable", "true");
+        props.put("mail.smtp.host", SMTP_HOST);
+        props.put("mail.smtp.port", SMTP_PORT);
+        return props;
+    }
+
+    private Message createMessage(Session session, String recipientEmail,
+                                  String code) throws MessagingException {
+        Message message = new MimeMessage(session);
+        message.setFrom(new InternetAddress(SENDER_EMAIL));
+        message.setRecipients(
+                Message.RecipientType.TO,
+                InternetAddress.parse(recipientEmail)
+        );
+        message.setSubject(SUBJECT);
+        message.setText("您的注册验证码是: " + code +
+                "\n\n请在应用中输入此代码完成注册。");
+        return message;
+    }
+
+    // R2: 实际发送验证邮件
+    public boolean sendVerificationEmail(String recipientEmail, String code) {
+        if (SENDER_EMAIL == null || SENDER_PASSWORD == null) {
+            System.err.println("错误: 邮件发送凭证未设置。");
+            return false;
+        }
+
+        Session session = Session.getInstance(getMailProperties(), new Authenticator() {
+            @Override
+            protected PasswordAuthentication getPasswordAuthentication() {
+                return new PasswordAuthentication(SENDER_EMAIL, SENDER_PASSWORD);
+            }
+        });
+
+        try {
+            Message message = createMessage(session, recipientEmail, code);
+            Transport.send(message);
+            return true;
+
+        } catch (MessagingException e) {
+            System.err.println("邮件发送失败: " + e.getMessage());
+            return false;
+        }
+    }
+}
diff --git a/src/util/ExpressionUtils.java b/src/util/ExpressionUtils.java
new file mode 100644
index 0000000..02d59a1
--- /dev/null
+++ b/src/util/ExpressionUtils.java
@@ -0,0 +1,358 @@
+package util;
+
+import generator.Problem;
+
+import java.util.*;
+
+public class ExpressionUtils {
+    private static Random rand = new Random();
+
+    private static final String[] OPS_PRIMARY = {"+", "-", "*", "/"};
+    private static final String[] OPS_MIDDLE = {"+", "-", "*", "/"};
+    //private static final String[] OPS_HIGH = {"+", "-", "*", "/", "^2", "sqrt"};
+
+
+    public static String randomNumber() {
+        return String.valueOf(rand.nextInt(100) + 1);
+    }
+
+    // --- 表达式求解和选项生成辅助方法 ---
+
+    public static double solveExpression(String expr) {
+    	// 预处理表达式，确保格式正确
+        String parsableExpr = expr
+            .replaceAll("(\\d+|\\([^)]+\\))\\^2", "pow($1, 2)")  // 处理平方
+            .replaceAll("sqrt\\s+(\\d+)", "sqrt($1)")  // 处理缺少括号的sqrt
+            .replaceAll("\\s+", " ");  // 标准化空格
+
+        try {
+            return new Object() {
+                int pos = -1, ch;
+
+                void nextChar() {
+                    ch = (++pos < parsableExpr.length()) ? parsableExpr.charAt(pos) : -1;
+                }
+
+                boolean eat(int charToEat) {
+                    while (ch == ' ') nextChar();
+                    if (ch == charToEat) {
+                        nextChar();
+                        return true;
+                    }
+                    return false;
+                }
+
+                double parse() {
+                    nextChar();
+                    double x = parseExpression();
+                    if (pos < parsableExpr.length()) throw new RuntimeException("Unexpected: " + (char) ch);
+                    return x;
+                }
+
+                double parseExpression() {
+                    double x = parseTerm();
+                    for (; ; ) {
+                        if (eat('+')) x += parseTerm(); // addition
+                        else if (eat('-')) x -= parseTerm(); // subtraction
+                        else return x;
+                    }
+                }
+
+                double parseTerm() {
+                    double x = parseFactor();
+                    for (; ; ) {
+                        if (eat('*')) x *= parseFactor(); // multiplication
+                        else if (eat('/')) { // division
+                            double divisor = parseFactor();
+                            if (divisor == 0) throw new ArithmeticException("Division by zero");
+                            x /= divisor;
+                        } else return x;
+                    }
+                }
+
+                double parseFactor() {
+                    if (eat('+')) return parseFactor(); // unary plus
+                    if (eat('-')) return -parseFactor(); // unary minus
+
+                    double x;
+                    int startPos = this.pos;
+                    if (eat('(')) { // parentheses
+                        x = parseExpression();
+                        eat(')');
+                    } else if ((ch >= '0' && ch <= '9') || ch == '.') { // numbers
+                        while ((ch >= '0' && ch <= '9') || ch == '.') nextChar();
+                        x = Double.parseDouble(parsableExpr.substring(startPos, this.pos));
+                    } else if (ch >= 'a' && ch <= 'z') { // functions
+                        while (ch >= 'a' && ch <= 'z') nextChar();
+                        String func = parsableExpr.substring(startPos, this.pos);
+                        x = parseFactor();
+                        switch (func) {
+                            case "sqrt":
+                                x = Math.sqrt(x);
+                                break;
+                            case "sin":
+                                x = Math.sin(Math.toRadians(x));
+                                break;
+                            case "cos":
+                                x = Math.cos(Math.toRadians(x));
+                                break;
+                            case "tan":
+                                x = Math.tan(Math.toRadians(x));
+                                break;
+                            case "pow":
+                                eat(',');
+                                double y = parseExpression();
+                                x = Math.pow(x, y);
+                                eat(')');
+                                break;
+                            default:
+                                throw new RuntimeException("Unknown function: " + func);
+                        }
+                    } else {
+                        throw new RuntimeException("Unexpected: " + (char) ch);
+                    }
+
+                    return x;
+                }
+            }.parse();
+        } catch (Exception e) {
+        	System.err.println("Error parsing expression: '" + expr + "'. Parsable version: '" + parsableExpr + "'. Error: " + e.getMessage());
+            return Double.NaN;
+        }
+    }
+
+
+    private static String formatResult(double result) {
+        if (Double.isNaN(result)) {
+            return "Error";
+        }
+        if (Math.abs(result - Math.round(result)) < 0.0001) {
+            return String.valueOf((int) Math.round(result));
+        }
+        return String.format("%.2f", result);
+    }
+
+    /**
+     * MODIFICATION: 确保为整数答案生成整数干扰项
+     */
+    private static String generateDistractor(double correctResult, List<String> existingOptions) {
+        if (Double.isNaN(correctResult)) {
+            return String.valueOf(rand.nextInt(100));
+        }
+
+        // 检查正确答案是否为整数
+        boolean isIntegerResult = Math.abs(correctResult - Math.round(correctResult)) < 0.0001;
+
+        double distractor;
+        String distractorStr;
+
+        do {
+            if (isIntegerResult) {
+                // 生成一个整数干扰项
+                int offset = rand.nextInt(20) + 1; // 扩大随机范围以避免重复
+                distractor = rand.nextBoolean() ? Math.round(correctResult) + offset : Math.round(correctResult) - offset;
+                // 确保干扰项不为负数
+                if (distractor < 0) {
+                    distractor = Math.round(correctResult) + offset;
+                }
+            } else {
+                // 答案是小数，则生成小数干扰项
+                distractor = correctResult +
+                        (rand.nextInt(10) + 1) * (rand.nextBoolean() ? 1 : -1) +
+                        (rand.nextDouble() * 0.9);
+            }
+            distractorStr = formatResult(distractor);
+        } while (existingOptions.contains(distractorStr)); // 确保选项不重复
+        return distractorStr;
+    }
+
+
+    public static List<String> generateOptions(double correctResult) {
+        List<String> options = new ArrayList<>();
+        options.add(formatResult(correctResult));
+
+        for (int i = 0; i < 3; i++) {
+            options.add(generateDistractor(correctResult, options));
+        }
+
+        Collections.shuffle(options);
+        return options;
+    }
+
+    public static Problem createProblem(String expression) {
+        double result = solveExpression(expression);
+        
+        // 如果解析失败，返回null，让调用者重新生成
+        if (Double.isNaN(result)) {
+            return null;
+        }
+        
+        String correctAnswerOption = formatResult(result);
+        List<String> options = generateOptions(result);
+        return new Problem(expression, result, options, correctAnswerOption);
+    }
+
+    // --- 题目生成方法 ---
+
+    private static int getDivisor(int dividend) {
+        List<Integer> divisors = new ArrayList<>();
+        for (int j = 1; j <= dividend; j++) {
+            if (dividend % j == 0) {
+                divisors.add(j);
+            }
+        }
+        return divisors.get(rand.nextInt(divisors.size()));
+    }
+
+    /**
+     * MODIFICATION: 增加答案非负、括号数量和操作数关联的逻辑
+     */
+    public static Problem generatePrimaryExpr() {
+        Problem problem;
+        double result;
+
+        do {
+            // 生成 2 到 4 个操作数
+            int operands = rand.nextInt(3) + 2;
+            List<String> parts = new ArrayList<>();
+
+            for (int i = 0; i < operands; i++) {
+                if (i > 0) {
+                    parts.add(OPS_PRIMARY[rand.nextInt(OPS_PRIMARY.length)]);
+                }
+
+                // 仅当操作数 >= 3 时，才有可能生成括号
+                if (operands >= 3 && rand.nextBoolean() && i < operands - 1) {
+                    int num1 = rand.nextInt(50) + 1;
+                    String innerOp = OPS_PRIMARY[rand.nextInt(OPS_PRIMARY.length)];
+                    int num2;
+                    if (innerOp.equals("/")) {
+                        num2 = getDivisor(num1);
+                    } else {
+                        num2 = rand.nextInt(50) + 1;
+                    }
+                    parts.add("(" + num1 + " " + innerOp + " " + num2 + ")");
+                    i++; // 括号表达式计为2个操作数
+                } else {
+                    int num;
+                    if (i > 0 && parts.get(parts.size() - 1).equals("/")) {
+                        String dividendStr = parts.get(parts.size() - 2);
+                        if (dividendStr.startsWith("(")) {
+                            // 为避免 (a+b)/c 这种复杂情况无法保证整数结果，直接替换运算符
+                            parts.set(parts.size() - 1, OPS_PRIMARY[rand.nextInt(3)]); // +, -, *
+                            num = rand.nextInt(100) + 1;
+                        } else {
+                            int dividend = Integer.parseInt(dividendStr);
+                            num = getDivisor(dividend);
+                        }
+                    } else {
+                        num = rand.nextInt(100) + 1;
+                    }
+                    parts.add(String.valueOf(num));
+                }
+            }
+            String expression = String.join(" ", parts);
+            problem = createProblem(expression);
+            result = problem.getResult();
+            // 循环直到答案为非负整数
+        } while (result < 0 || Double.isNaN(result) || Math.abs(result - Math.round(result)) > 0.0001);
+
+        return problem;
+    }
+
+
+    public static Problem generateMiddleExpr() {
+        int operands = rand.nextInt(5) + 1;
+        StringBuilder expr = new StringBuilder();
+        boolean hasSquareOrSqrt = false;
+
+        for (int i = 0; i < operands; i++) {
+            if (i > 0) {
+                expr.append(" ").append(OPS_MIDDLE[rand.nextInt(OPS_MIDDLE.length)]).append(" ");
+            }
+            int num = rand.nextInt(100) + 1;
+            if (!hasSquareOrSqrt && rand.nextBoolean()) {
+                expr.append(rand.nextBoolean() ? "sqrt(" + num + ")" : num + "^2");
+                hasSquareOrSqrt = true;
+            } else {
+                expr.append(num);
+            }
+        }
+
+        if (!hasSquareOrSqrt) {
+            expr.append(" + ").append(rand.nextInt(50) + 1).append("^2");
+        }
+
+        return createProblem(expr.toString());
+    }
+
+    public static Problem generateHighExpr() {
+        int attempts = 0;
+        final int maxAttempts = 10;
+        
+        while (attempts < maxAttempts) {
+            int operands = rand.nextInt(3) + 2; // 2-4个操作数
+            StringBuilder expr = new StringBuilder();
+            boolean hasTrig = false;
+
+            for (int i = 0; i < operands; i++) {
+                if (i > 0) {
+                    String[] validOps = {"+", "-", "*", "/"};
+                    String op = validOps[rand.nextInt(validOps.length)];
+                    expr.append(" ").append(op).append(" ");
+                }
+                
+                // 强制至少有一个操作数是三角函数
+                if (!hasTrig && (i == operands - 1 || rand.nextBoolean())) {
+                    String[] funcs = {"sin", "cos", "tan"};
+                    String func = funcs[rand.nextInt(funcs.length)];
+                    int angle = rand.nextInt(90) + 1; // 1-90度
+                    expr.append(func).append("(").append(angle).append(")");
+                    hasTrig = true;
+                } else {
+                    // 其他操作数可以是普通数字、平方或开方
+                    int num = rand.nextInt(100) + 1;
+                    if (rand.nextBoolean() && hasTrig) { // 确保已经有三角函数后再添加其他函数
+                        if (rand.nextBoolean()) {
+                            expr.append(num).append("^2");
+                        } else {
+                            expr.append("sqrt(").append(num).append(")");
+                        }
+                    } else {
+                        expr.append(num);
+                    }
+                }
+            }
+
+            // 如果没有三角函数，强制添加一个
+            if (!hasTrig) {
+                String[] funcs = {"sin", "cos", "tan"};
+                String func = funcs[rand.nextInt(funcs.length)];
+                int angle = rand.nextInt(90) + 1;
+                
+                if (rand.nextBoolean()) {
+                    // 在开头添加
+                    expr.insert(0, func + "(" + angle + ") + ");
+                } else {
+                    // 在结尾添加
+                    expr.append(" + ").append(func).append("(").append(angle).append(")");
+                }
+                hasTrig = true;
+            }
+
+            String expression = expr.toString();
+            
+            // 验证表达式
+            Problem problem = createProblem(expression);
+            if (problem != null) {
+                return problem;
+            }
+            
+            attempts++;
+            System.err.println("生成高中题目失败，尝试次数: " + attempts + ", 表达式: " + expression);
+        }
+        
+        return createProblem("sin(30) + cos(60)");
+    }
+    
+}
\ No newline at end of file
diff --git a/src/util/FileUtils.java b/src/util/FileUtils.java
new file mode 100644
index 0000000..ce0c7f7
--- /dev/null
+++ b/src/util/FileUtils.java
@@ -0,0 +1,79 @@
+package util;
+
+import generator.Problem;
+import java.io.*;
+import java.text.SimpleDateFormat;
+import java.util.*;
+
+public class FileUtils {
+    private static final String FOLDER_PATH = "exams/";
+
+    public static String getUserFolder(String username) {
+        String folder = FOLDER_PATH + username;
+        File dir = new File(folder);
+        if (!dir.exists()) {
+            dir.mkdirs();
+        }
+        return folder;
+    }
+
+    private static void processHistoryFile(File file, Set<String> history) {
+        try (BufferedReader br = new BufferedReader(new FileReader(file))) {
+            String line;
+            while ((line = br.readLine()) != null) {
+                if (!line.trim().isEmpty() && line.matches("^\\d+\\..*")) {
+                    // 仅提取题干 (表达式字符串) 用于查重
+                    history.add(line.substring(line.indexOf('.') + 1).trim());
+                }
+            }
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public static Set<String> loadHistory(String username) {
+        Set<String> history = new HashSet<>();
+        File dir = new File(getUserFolder(username));
+        File[] files = dir.listFiles((d, name) -> name.endsWith(".txt"));
+
+        if (files != null) {
+            for (File file : files) {
+                processHistoryFile(file, history);
+            }
+        }
+        return history;
+    }
+
+    private static void writeProblem(BufferedWriter bw, int index, Problem problem) throws IOException {
+        bw.write(index + "." + problem.getExpression());
+        bw.newLine();
+
+        char optionChar = 'A';
+        StringBuilder optionsLine = new StringBuilder();
+        for (String option : problem.getOptions()) {
+            optionsLine.append(optionChar++).append(". ").append(option).append("  ");
+        }
+
+        bw.write(optionsLine.toString().trim());
+        bw.newLine();
+        bw.write("答案: " + problem.getCorrectAnswerOption());
+        bw.newLine();
+        bw.newLine();
+    }
+
+    public static void saveProblems(String username, List<Problem> problems) {
+        String folder = getUserFolder(username);
+        String timestamp = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date());
+        String filename = folder + "/" + timestamp + ".txt";
+
+        try (BufferedWriter bw = new BufferedWriter(new FileWriter(filename))) {
+            int index = 1;
+            for (Problem problem : problems) {
+                writeProblem(bw, index++, problem);
+            }
+            System.out.println("卷子已保存到: " + filename);
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}
diff --git a/src/util/ModifyUtils.java b/src/util/ModifyUtils.java
new file mode 100644
index 0000000..ab02695
--- /dev/null
+++ b/src/util/ModifyUtils.java
@@ -0,0 +1,76 @@
+package util;
+
+import java.io.*;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Utility class to modify specific fields in user.txt.
+ * 替换了 ModifyClass.java 和 ModifyPassword.java。
+ */
+public class ModifyUtils {
+
+    private static List<String> readAllLines(String filePath, List<String> lines) throws IOException {
+        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                lines.add(line);
+            }
+        }
+        return lines;
+    }
+
+    private static void writeAllLines(String filePath, List<String> lines) throws IOException {
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filePath))) {
+            for (String l : lines) {
+                writer.write(l + System.lineSeparator());
+            }
+        }
+    }
+
+    private static int findTargetLine(List<String> lines, String targetName) {
+        for (int i = 0; i < lines.size(); i++) {
+            String line = lines.get(i).trim();
+            if (line.isEmpty()) continue;
+
+            String[] parts = line.split("\\s+");
+            if (parts.length > 0 && parts[0].equals(targetName)) {
+                return i; // 0-based index
+            }
+        }
+        return -1;
+    }
+
+    // 核心逻辑：修改文件中特定用户的某个字段 (0-based)
+    public static int modifyFileField(String filePath, String targetName,
+                                      int fieldIndex, String newValue) {
+        List<String> lines = new ArrayList<>();
+        try {
+            readAllLines(filePath, lines);
+        } catch (IOException e) {
+            System.err.println("读取文件错误: " + e.getMessage());
+            return -1;
+        }
+
+        int idx = findTargetLine(lines, targetName);
+        if (idx == -1) {
+            return -1;
+        }
+
+        String[] parts = lines.get(idx).trim().split("\\s+");
+        if (parts.length > fieldIndex) {
+            parts[fieldIndex] = newValue;
+            lines.set(idx, String.join(" ", parts));
+            try {
+                writeAllLines(filePath, lines);
+                return idx + 1; // 返回 1-based 行号
+            } catch (IOException e) {
+                System.err.println("写入文件错误: " + e.getMessage());
+                return -1;
+            }
+        } else {
+            System.out.println("目标行元素不足。");
+            return -1;
+        }
+    }
+}
\ No newline at end of file