用java语言编写一个学生选课管理系统的代码。要求1，实现课程信息打印、查询、录入、删除、修改功能。 2，实现学生信息打印、查询、录入、删除、修改功能。 管理端系统设置。仿真加密系统，实现密码防护、修改密码、注销功能。其中密码防护功能实现用户多次输入密码错误，系统将进入休眠状态，等待一段时间后用户才能重新输入密码，防止用户恶意登录。

好的，下面是一个简单的学生选课管理系统代码，满足您的要求：

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

public class Course {
    private String courseCode; // 课程代码
    private String courseName; // 课程名称
    private String teacher; // 授课教师
    private int credit; // 学分

    public Course(String courseCode, String courseName, String teacher, int credit) {
        this.courseCode = courseCode;
        this.courseName = courseName;
        this.teacher = teacher;
        this.credit = credit;
    }

    public String getCourseCode() {
        return courseCode;
    }

    public void setCourseCode(String courseCode) {
        this.courseCode = courseCode;
    }

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }

    public String getTeacher() {
        return teacher;
    }

    public void setTeacher(String teacher) {
        this.teacher = teacher;
    }

    public int getCredit() {
        return credit;
    }

    public void setCredit(int credit) {
        this.credit = credit;
    }
}

class Student {
    private String studentID; // 学生学号
    private String name; // 学生姓名
    private int credit; // 已修学分
    private List<Course> selectedCourses; // 已选课程

    public Student(String studentID, String name) {
        this.studentID = studentID;
        this.name = name;
        this.credit = 0;
        selectedCourses = new ArrayList<Course>();
    }

    public String getStudentID() {
        return studentID;
    }

    public void setStudentID(String studentID) {
        this.studentID = studentID;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getCredit() {
        return credit;
    }

    public void setCredit(int credit) {
        this.credit = credit;
    }

    public List<Course> getSelectedCourses() {
        return selectedCourses;
    }

    public void setSelectedCourses(List<Course> selectedCourses) {
        this.selectedCourses = selectedCourses;
    }
}

class CourseManager {
    private List<Course> courseList; // 课程列表

    public CourseManager() {
        courseList = new ArrayList<Course>();
    }

    public void printCourses() {
        System.out.println("课程列表：");
        for (Course course : courseList) {
            System.out.println(course.getCourseCode() + " " + course.getCourseName() + " " + course.getTeacher() + " "
                    + course.getCredit());
        }
    }

    public Course findCourse(String courseCode) {
        for (Course course : courseList) {
            if (course.getCourseCode().equals(courseCode)) {
                return course;
            }
        }
        return null;
    }

    public void addCourse() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入课程代码：");
        String courseCode = scanner.nextLine();
        System.out.print("请输入课程名称：");
        String courseName = scanner.nextLine();
        System.out.print("请输入授课教师：");
        String teacher = scanner.nextLine();
        System.out.print("请输入学分：");
        int credit = scanner.nextInt();
        scanner.nextLine();
        Course course = new Course(courseCode, courseName, teacher, credit);
        courseList.add(course);
        System.out.println("添加课程成功！");
    }

    public void deleteCourse() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要删除的课程代码：");
        String courseCode = scanner.nextLine();
        Course course = findCourse(courseCode);
        if (course != null) {
            courseList.remove(course);
            System.out.println("删除课程成功！");
        } else {
            System.out.println("没有找到该课程！");
        }
    }

    public void modifyCourse() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要修改的课程代码：");
        String courseCode = scanner.nextLine();
        Course course = findCourse(courseCode);
        if (course != null) {
            System.out.print("请输入新的课程名称（原名称：" + course.getCourseName() + "）：");
            String courseName = scanner.nextLine();
            System.out.print("请输入新的授课教师（原教师：" + course.getTeacher() + "）：");
            String teacher = scanner.nextLine();
            System.out.print("请输入新的学分（原学分：" + course.getCredit() + "）：");
            int credit = scanner.nextInt();
            scanner.nextLine();
            course.setCourseName(courseName);
            course.setTeacher(teacher);
            course.setCredit(credit);
            System.out.println("修改课程成功！");
        } else {
            System.out.println("没有找到该课程！");
        }
    }
}

class StudentManager {
    private List<Student> studentList; // 学生列表
    private CourseManager courseManager; // 课程管理器

    public StudentManager() {
        studentList = new ArrayList<Student>();
        courseManager = new CourseManager();
    }

    public void printStudents() {
        System.out.println("学生列表：");
        for (Student student : studentList) {
            System.out.println(student.getStudentID() + " " + student.getName() + " " + student.getCredit());
            System.out.println("已选课程：");
            for (Course course : student.getSelectedCourses()) {
                System.out.println(course.getCourseCode() + " " + course.getCourseName() + " " + course.getTeacher()
                        + " " + course.getCredit());
            }
        }
    }

    public Student findStudent(String studentID) {
        for (Student student : studentList) {
            if (student.getStudentID().equals(studentID)) {
                return student;
            }
        }
        return null;
    }

    public void addStudent() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入学生学号：");
        String studentID = scanner.nextLine();
        System.out.print("请输入学生姓名：");
        String name = scanner.nextLine();
        Student student = new Student(studentID, name);
        studentList.add(student);
        System.out.println("添加学生成功！");
    }

    public void deleteStudent() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要删除的学生学号：");
        String studentID = scanner.nextLine();
        Student student = findStudent(studentID);
        if (student != null) {
            studentList.remove(student);
            System.out.println("删除学生成功！");
        } else {
            System.out.println("没有找到该学生！");
        }
    }

    public void modifyStudent() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入要修改的学生学号：");
        String studentID = scanner.nextLine();
        Student student = findStudent(studentID);
        if (student != null) {
            System.out.print("请输入新的学生姓名（原姓名：" + student.getName() + "）：");
            String name = scanner.nextLine();
            student.setName(name);
            System.out.println("修改学生成功！");
        } else {
            System.out.println("没有找到该学生！");
        }
    }

    public void selectCourse() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入学生学号：");
        String studentID = scanner.nextLine();
        Student student = findStudent(studentID);
        if (student == null) {
            System.out.println("没有找到该学生！");
            return;
        }
        System.out.println("该学生已选课程：");
        for (Course course : student.getSelectedCourses()) {
            System.out.println(course.getCourseCode() + " " + course.getCourseName() + " " + course.getTeacher()
                    + " " + course.getCredit());
        }
        System.out.println("可选课程列表：");
        courseManager.printCourses();
        System.out.print("请输入要选修的课程代码：");
        String courseCode = scanner.nextLine();
        Course course = courseManager.findCourse(courseCode);
        if (course == null) {
            System.out.println("没有找到该课程！");
            return;
        }
        if (student.getCredit() + course.getCredit() > 20) {
            System.out.println("学分已超过上限，不能选修该课程！");
            return;
        }
        student.getSelectedCourses().add(course);
        student.setCredit(student.getCredit() + course.getCredit());
        System.out.println("选课成功！");
    }

    public void dropCourse() {
        Scanner scanner = new Scanner(System.in);
        System.out.print("请输入学生学号：");
        String studentID = scanner.nextLine();
        Student student = findStudent(studentID);
        if (student == null) {
            System.out.println("没有找到该学生！");
            return;
        }
        System.out.println("该学生已选课程：");
        for (int i = 0; i < student.getSelectedCourses().size(); i++) {
            Course course = student.getSelectedCourses().get(i);
            System.out.println((i + 1) + ". " + course.getCourseCode() + " " + course.getCourseName() + " "
                    + course.getTeacher() + " " + course.getCredit());
        }
        System.out.print("请输入要退选的课程编号：");
        int index = scanner.nextInt() - 1;
        scanner.nextLine();
        if (index < 0 || index >= student.getSelectedCourses().size()) {
            System.out.println("输入有误！");
            return;
        }
        Course course = student.getSelectedCourses().get(index);
        student.getSelectedCourses().remove(index);
        student.setCredit(student.getCredit() - course.getCredit());
        System.out.println("退课成功！");
    }
}

class SecurityManager {
    private Map<String, String> userMap; // 用户名和密码映射表
    private Map<String, Integer> attemptMap; // 用户名和尝试次数映射表
    private static final int MAX_ATTEMPTS = 3; // 最大尝试次数
    private static final long SLEEP_TIME = 5000; // 休眠时间（毫秒）

    public SecurityManager() {
        userMap = new HashMap<String, String>();
        attemptMap = new HashMap<String, Integer>();
    }

    public void addUser(String username, String password) {
        userMap.put(username, password);
    }

    public void deleteUser(String username) {
        userMap.remove(username);