写一个java考试系统的程序，系统应该能够管理不同的考试科目和试题。 学生应该能够注册、登录和参加考试。 考试应该有一定的时间限制，超时后自动提交。 学生应该能够查看自己的考试成绩和历史记录。 教师应该能够添加、修改和删除考试科目和试题，并查看学生的成绩和历史记录。

以下是一个简单的Java考试系统程序示例，包含了基本的考试管理和用户管理功能：

import java.util.ArrayList;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;

public class ExamSystem {
    private Map<String, ExamSubject> subjects; // 考试科目
    private Map<String, Student> students; // 学生
    private Map<String, Teacher> teachers; // 教师
    private Scanner scanner;

    public ExamSystem() {
        subjects = new HashMap<>();
        students = new HashMap<>();
        teachers = new HashMap<>();
        scanner = new Scanner(System.in);
    }

    // 添加考试科目
    public void addSubject() {
        System.out.print("请输入科目名称：");
        String name = scanner.nextLine();
        System.out.print("请输入考试时间（yyyy-MM-dd HH:mm:ss）：");
        String timeStr = scanner.nextLine();
        Date time = DateUtil.parse(timeStr);
        System.out.print("请输入考试时长（分钟）：");
        int duration = scanner.nextInt();
        System.out.print("请输入总分数：");
        int totalScore = scanner.nextInt();
        scanner.nextLine();
        ExamSubject subject = new ExamSubject(name, time, duration, totalScore);
        subjects.put(name, subject);
        System.out.println("添加科目成功！");
    }

    // 添加试题
    public void addQuestion() {
        System.out.print("请输入科目名称：");
        String name = scanner.nextLine();
        ExamSubject subject = subjects.get(name);
        if (subject == null) {
            System.out.println("科目不存在！");
            return;
        }

        System.out.print("请输入题目类型（1：单选题，2：多选题，3：判断题）：");
        int type = scanner.nextInt();
        scanner.nextLine();
        System.out.print("请输入题目内容：");
        String content = scanner.nextLine();
        System.out.print("请输入选项个数：");
        int optionCount = scanner.nextInt();
        scanner.nextLine();
        String[] options = new String[optionCount];
        for (int i = 0; i < optionCount; i++) {
            System.out.print("请输入选项" + (i + 1) + "：");
            options[i] = scanner.nextLine();
        }
        System.out.print("请输入答案（单选题和判断题只需输入一个答案，多选题需要用逗号分隔多个答案）：");
        String answer = scanner.nextLine();
        System.out.print("请输入分值：");
        int score = scanner.nextInt();
        scanner.nextLine();
        Question question = new Question(type, content, options, answer, score);
        subject.addQuestion(question);
        System.out.println("添加试题成功！");
    }

    // 注册学生
    public void registerStudent() {
        System.out.print("请输入用户名：");
        String username = scanner.nextLine();
        System.out.print("请输入密码：");
        String password = scanner.nextLine();
        System.out.print("请输入邮箱：");
        String email = scanner.nextLine();
        System.out.print("请输入真实姓名：");
        String realName = scanner.nextLine();
        System.out.print("请输入班级：");
        String className = scanner.nextLine();
        Student student = new Student(username, password, email, realName, className);
        students.put(username, student);
        System.out.println("注册成功！");
    }

    // 注册教师
    public void registerTeacher() {
        System.out.print("请输入用户名：");
        String username = scanner.nextLine();
        System.out.print("请输入密码：");
        String password = scanner.nextLine();
        System.out.print("请输入邮箱：");
        String email = scanner.nextLine();
        System.out.print("请输入真实姓名：");
        String realName = scanner.nextLine();
        Teacher teacher = new Teacher(username, password, email, realName);
        teachers.put(username, teacher);
        System.out.println("注册成功！");
    }

    // 学生登录
    public void studentLogin() {
        System.out.print("请输入用户名：");
        String username = scanner.nextLine();
        System.out.print("请输入密码：");
        String password = scanner.nextLine();
        Student student = students.get(username);
        if (student == null || !student.getPassword().equals(password)) {
            System.out.println("用户名或密码错误！");
            return;
        }
        studentMenu(student);
    }

    // 教师登录
    public void teacherLogin() {
        System.out.print("请输入用户名：");
        String username = scanner.nextLine();
        System.out.print("请输入密码：");
        String password = scanner.nextLine();
        Teacher teacher = teachers.get(username);
        if (teacher == null || !teacher.getPassword().equals(password)) {
            System.out.println("用户名或密码错误！");
            return;
        }
        teacherMenu(teacher);
    }

    // 学生菜单
    public void studentMenu(Student student) {
        while (true) {
            System.out.println("欢迎，" + student.getRealName() + "！");
            System.out.println("1. 参加考试");
            System.out.println("2. 查看成绩");
            System.out.println("3. 查看历史记录");
            System.out.println("4. 退出登录");
            System.out.print("请选择操作：");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 1:
                    takeExam(student);
                    break;
                case 2:
                    viewScore(student);
                    break;
                case 3:
                    viewHistory(student);
                    break;
                case 4:
                    return;
                default:
                    System.out.println("无效的选择！");
                    break;
            }
        }
    }

    // 教师菜单
    public void teacherMenu(Teacher teacher) {
        while (true) {
            System.out.println("欢迎，" + teacher.getRealName() + "！");
            System.out.println("1. 添加考试科目");
            System.out.println("2. 添加试题");
            System.out.println("3. 查看学生成绩");
            System.out.println("4. 查看历史记录");
            System.out.println("5. 退出登录");
            System.out.print("请选择操作：");
            int choice = scanner.nextInt();
            scanner.nextLine();
            switch (choice) {
                case 1:
                    addSubject();
                    break;
                case 2:
                    addQuestion();
                    break;
                case 3:
                    viewStudentScore();
                    break;
                case 4:
                    viewHistory(null);
                    break;
                case 5:
                    return;
                default:
                    System.out.println("无效的选择！");
                    break;
            }
        }
    }

    // 参加考试
    public void takeExam(Student student) {
        System.out.print("请输入科目名称：");
        String name = scanner.nextLine();
        ExamSubject subject = subjects.get(name);
        if (subject == null) {
            System.out.println("科目不存在！");
            return;
        }

        ExamRecord record = new ExamRecord(student, subject);
        ArrayList<Question> questions = subject.getQuestions();
        int i = 1;
        for (Question question : questions) {
            System.out.println(i + ". " + question);
            i++;
        }
        System.out.println("考试开始！");
        long beginTime = System.currentTimeMillis();
        while (true) {
            long currentTime = System.currentTimeMillis();
            if (currentTime - beginTime >= subject.getDuration() * 60 * 1000) {
                System.out.println("考试时间到！");
                break;
            }
            System.out.println("剩余时间：" + (subject.getDuration() * 60 - (currentTime - beginTime) / 1000) + "秒");
            System.out.print("请输入答案序号（多选题用逗号分隔）：");
            String answer = scanner.nextLine();
            try {
                int[] answerIds = parseAnswer(answer);
                for (int id : answerIds) {
                    record.addAnswer(questions.get(i - 1), id);
                }
            } catch (Exception e) {
                System.out.println("答案格式错误！");
            }
            i++;
            if (i > questions.size()) {
                System.out.println("考试结束！");
                break;
            }
        }
        record.calculateScore();
        System.out.println("得分：" + record.getScore());
        student.addScore(subject.getName(), record.getScore());
    }

    // 查看成绩
    public void viewScore(Student student) {
        System.out.print("请输入科目名称：");
        String name = scanner.nextLine();
        ExamSubject subject = subjects.get(name);
        if (subject == null) {
            System.out.println("科目不存在！");
            return;
        }
        Integer score = student.getScores().get(name);
        if (score == null) {
            System.out.println("还没有参加过该科目的考试！");
        } else {
            System.out.println("得分：" + score);
        }
    }

    // 查看历史记录
    public void viewHistory(User user) {
        System.out.print("请输入用户名（留空表示查看所有用户）：");
        String username = scanner.nextLine();
        if ("".equals(username.trim())) {
            for (Map.Entry<String, Student> entry : students.entrySet()) {
                Student student = entry.getValue();
                System.out.println(student.getRealName() + "的历史记录：");
                for (ExamRecord record : student.getRecords()) {
                    System.out.println(record);
                }
            }
            for (Map.Entry<String, Teacher> entry : teachers.entrySet()) {
                Teacher teacher = entry.getValue();
                System.out.println(teacher.getRealName() + "的历史记录：");
                for (ExamRecord record : teacher.getRecords()) {
                    System.out.println(record);
                }
            }
        } else {
            User u = students.get(username);
            if (u == null) {
                u = teachers.get(username);
                if (u == null) {
                    System.out.println("用户不存在！");
                    return;
                }
            }
            System.out.println(u.getRealName() + "的历史记录：");
            for (ExamRecord record : u.getRecords()) {
                System.out.println(record);
            }
        }
    }

    // 查看学生成绩
    public void viewStudentScore() {
        System.out.print("请输入用户名：");
        String username = scanner.nextLine();
        Student student = students.get(username);
        if (student == null) {
            System.out.println("学生不存在！");
            return;
        }
        for (Map.Entry<String, Integer> entry : student.getScores().entrySet()) {
            System.out.println(entry.getKey() + "：" + entry.getValue());
        }
    }

    // 解析答案
    private int[] parseAnswer(String answer) throws Exception {
        String[] split = answer.split(",");
        int[] result = new int[split.length];
        for (int i = 0; i < split.length; i++) {
            try {
                result[i] = Integer.parseInt(split[i].trim());
            } catch (NumberFormatException e) {
                throw new Exception("答案格式错误