简单的Java小项目

学生选课系统

在控制台输入输出信息：

在eclipse上面的超级简单文件结构：

Main.java

package experiment_4;import java.util.*;
import java.io.*;public class Main {public static List<Course> courseList = new ArrayList<>();public static List<Teacher> teacherList = new ArrayList<>();public static List<Student> studentList = new ArrayList<>();public static void main(String[] args) {loadData();Scanner scanner = new Scanner(System.in);while (true) {System.out.println("===== 欢迎使用学生选课系统 =====");System.out.print("请输入用户名（输入exit退出）：");String username = scanner.nextLine();if (username.equals("exit")) {saveData();break;}System.out.print("请输入密码：");String password = scanner.nextLine();User user = null;if (username.equals("admin")) {user = new Admin(username, courseList, teacherList, studentList);} else {user = findUserByUsername(username);}if (user == null) {System.out.println("用户不存在！");continue;}if (!user.verifyPassword(password)) {System.out.println("密码错误！");continue;}user.operate();}scanner.close();}private static User findUserByUsername(String username) {for (Teacher teacher : teacherList) {if (teacher.getUsername().equals(username)) {return teacher;}}for (Student student : studentList) {if (student.getUsername().equals(username)) {return student;}}return null;}private static void loadData() {try (ObjectInputStream ois1 = new ObjectInputStream(new FileInputStream("C:\\Users\\86183\\Desktop\\courses.txt"));ObjectInputStream ois2 = new ObjectInputStream(new FileInputStream("C:\\Users\\86183\\Desktop\\teachers.txt"));ObjectInputStream ois3 = new ObjectInputStream(new FileInputStream("C:\\Users\\86183\\Desktop\\students.txt"))) {courseList = (List<Course>) ois1.readObject();teacherList = (List<Teacher>) ois2.readObject();studentList = (List<Student>) ois3.readObject();} catch (Exception e) {System.out.println("初次运行，未找到数据文件。");}}private static void saveData() {try (ObjectOutputStream oos1 = new ObjectOutputStream(new FileOutputStream("C:\\Users\\86183\\Desktop\\courses.txt"));ObjectOutputStream oos2 = new ObjectOutputStream(new FileOutputStream("C:\\Users\\86183\\Desktop\\teachers.txt"));ObjectOutputStream oos3 = new ObjectOutputStream(new FileOutputStream("C:\\Users\\86183\\Desktop\\students.txt"))) {oos1.writeObject(courseList);oos2.writeObject(teacherList);oos3.writeObject(studentList);System.out.println("数据已保存。");} catch (IOException e) {e.printStackTrace();}}
}

Admin.java

package experiment_4;import java.util.*;
import java.io.*;public class Admin extends User {private List<Course> courseList;private List<Teacher> teacherList;private List<Student> studentList;public Admin(String username, List<Course> courseList, List<Teacher> teacherList, List<Student> studentList) {super(username);this.courseList = courseList;this.teacherList = teacherList;this.studentList = studentList;}@Overridepublic void displayMenu() {System.out.println("===== 管理员菜单 =====");System.out.println("1. 添加课程");System.out.println("2. 删除课程");System.out.println("3. 按照选课人数排序");System.out.println("4. 显示课程清单");System.out.println("5. 修改授课教师");System.out.println("6. 显示学生列表");System.out.println("7. 显示教师列表");System.out.println("8. 恢复学生和教师初始密码");System.out.println("9. 添加老师和学生");System.out.println("10. 删除老师和学生");System.out.println("0. 退出");System.out.print("请选择操作：");}@Overridepublic void operate() {Scanner scanner = new Scanner(System.in);while (true) {displayMenu();int choice = scanner.nextInt();switch (choice) {case 1:addCourse();break;case 2:deleteCourse();break;case 3:sortCoursesByStudentNumber();break;case 4:displayCourseList();break;case 5:modifyCourseTeacher();break;case 6:displayStudentList();break;case 7:displayTeacherList();break;case 8:resetPasswords();break;case 9:addUser();break;case 10:deleteUser();break;case 0:System.out.println("退出管理员系统。");return;default:System.out.println("无效的选择，请重新输入。");}}}private void addCourse() {Scanner scanner = new Scanner(System.in);System.out.print("请输入课程ID：");String courseID = scanner.nextLine();System.out.print("请输入课程名称：");String courseName = scanner.nextLine();System.out.print("请输入授课教师用户名：");String teacherName = scanner.nextLine();Teacher teacher = findTeacherByUsername(teacherName);if (teacher == null) {System.out.println("教师不存在！");return;}System.out.print("课程类型（1.必修 2.选修）：");int type = scanner.nextInt();if (type == 1) {Course course = new CompulsoryCourse(courseID, courseName, teacher);courseList.add(course);// 所有学生自动加入必修课for (Student student : studentList) {student.getCoursesEnrolled().add(course);course.incrementStudentNumber();}} else if (type == 2) {System.out.print("请输入选修课最大人数：");int maxStudents = scanner.nextInt();Course course = new ElectiveCourse(courseID, courseName, teacher, maxStudents);courseList.add(course);} else {System.out.println("无效的课程类型！");return;}teacher.getCoursesTaught().add(courseList.get(courseList.size() - 1));System.out.println("课程添加成功！");}private void deleteCourse() {Scanner scanner = new Scanner(System.in);System.out.print("请输入要删除的课程ID：");String courseID = scanner.nextLine();Course course = findCourseByID(courseID);if (course != null) {courseList.remove(course);// 从教师和学生的课程列表中删除该课程course.getTeacher().getCoursesTaught().remove(course);for (Student student : studentList) {student.getCoursesEnrolled().remove(course);}System.out.println("课程删除成功！");} else {System.out.println("课程不存在！");}}private void sortCoursesByStudentNumber() {Collections.sort(courseList, new Comparator<Course>() {@Overridepublic int compare(Course c1, Course c2) {return c2.getNumberOfStudents() - c1.getNumberOfStudents();}});System.out.println("课程已按照选课人数排序！");}private void displayCourseList() {System.out.println("===== 课程清单 =====");for (Course course : courseList) {System.out.println(course);}}private void modifyCourseTeacher() {Scanner scanner = new Scanner(System.in);System.out.print("请输入要修改的课程ID：");String courseID = scanner.nextLine();Course course = findCourseByID(courseID);if (course == null) {System.out.println("课程不存在！");return;}System.out.print("请输入新教师的用户名：");String teacherName = scanner.nextLine();Teacher newTeacher = findTeacherByUsername(teacherName);if (newTeacher == null) {System.out.println("教师不存在！");return;}// 更新教师信息course.getTeacher().getCoursesTaught().remove(course);course.setTeacher(newTeacher);newTeacher.getCoursesTaught().add(course);System.out.println("授课教师修改成功！");}private void displayStudentList() {System.out.println("===== 学生列表 =====");for (Student student : studentList) {System.out.println(student.getUsername());}}private void displayTeacherList() {System.out.println("===== 教师列表 =====");for (Teacher teacher : teacherList) {System.out.println(teacher.getUsername());}}private void resetPasswords() {for (Student student : studentList) {student.setPassword("123456");}for (Teacher teacher : teacherList) {teacher.setPassword("123456");}System.out.println("学生和教师密码已重置为初始密码！");}private void addUser() {Scanner scanner = new Scanner(System.in);System.out.print("添加对象（1.教师 2.学生）：");int type = scanner.nextInt();scanner.nextLine(); // 消耗换行符System.out.print("请输入用户名：");String username = scanner.nextLine();if (type == 1) {Teacher teacher = new Teacher(username);teacherList.add(teacher);System.out.println("教师添加成功！");} else if (type == 2) {Student student = new Student(username);// 将学生加入所有必修课for (Course course : courseList) {if (course instanceof CompulsoryCourse) {student.getCoursesEnrolled().add(course);course.incrementStudentNumber();}}studentList.add(student);System.out.println("学生添加成功！");} else {System.out.println("无效的类型！");}}private void deleteUser() {Scanner scanner = new Scanner(System.in);System.out.print("删除对象（1.教师 2.学生）：");int type = scanner.nextInt();scanner.nextLine(); // 消耗换行符System.out.print("请输入用户名：");String username = scanner.nextLine();if (type == 1) {Teacher teacher = findTeacherByUsername(username);if (teacher != null) {teacherList.remove(teacher);// 从课程中移除教师for (Course course : courseList) {if (course.getTeacher().equals(teacher)) {course.setTeacher(null);}}System.out.println("教师删除成功！");} else {System.out.println("教师不存在！");}} else if (type == 2) {Student student = findStudentByUsername(username);if (student != null) {studentList.remove(student);// 从课程中移除学生for (Course course : student.getCoursesEnrolled()) {course.decrementStudentNumber();}System.out.println("学生删除成功！");} else {System.out.println("学生不存在！");}} else {System.out.println("无效的类型！");}}private Teacher findTeacherByUsername(String username) {for (Teacher teacher : teacherList) {if (teacher.getUsername().equals(username)) {return teacher;}}return null;}private Student findStudentByUsername(String username) {for (Student student : studentList) {if (student.getUsername().equals(username)) {return student;}}return null;}private Course findCourseByID(String courseID) {for (Course course : courseList) {if (course.getCourseID().equals(courseID)) {return course;}}return null;}
}

CompulsoryCourse.java

package experiment_4;public class CompulsoryCourse extends Course {public CompulsoryCourse(String courseID, String courseName, Teacher teacher) {super(courseID, courseName, teacher);}@Overridepublic String toString() {return super.toString() + "（必修课）";}
}

Course.java

package experiment_4;import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;public class Course implements Serializable {protected String courseID;protected String courseName;protected Teacher teacher;protected int numberOfStudents;protected List<Student> enrolledStudents;public Course(String courseID, String courseName, Teacher teacher) {this.courseID = courseID;this.courseName = courseName;this.teacher = teacher;this.numberOfStudents = 0;this.enrolledStudents = new ArrayList<>();}public String getCourseID() {return courseID;}public Teacher getTeacher() {return teacher;}public void setTeacher(Teacher teacher) {this.teacher = teacher;}public int getNumberOfStudents() {return numberOfStudents;}public void incrementStudentNumber() {this.numberOfStudents++;}public void decrementStudentNumber() {this.numberOfStudents--;}public List<Student> getEnrolledStudents() {return enrolledStudents;}@Overridepublic String toString() {return "课程ID：" + courseID + ", 课程名称：" + courseName + ", 授课教师：" + teacher.getUsername() +", 选课人数：" + numberOfStudents;}
}

ElectiveCourse.java

package experiment_4;public class ElectiveCourse extends Course {private int maxStudents;public ElectiveCourse(String courseID, String courseName, Teacher teacher, int maxStudents) {super(courseID, courseName, teacher);this.maxStudents = maxStudents;}public int getMaxStudents() {return maxStudents;}@Overridepublic String toString() {return super.toString() + ", 最大选课人数：" + maxStudents + "（选修课）";}
}

Student.java

package experiment_4;import java.util.*;public class Student extends User {private List<Course> coursesEnrolled;public Student(String username) {super(username);this.coursesEnrolled = new ArrayList<>();}@Overridepublic void displayMenu() {System.out.println("===== 学生菜单 =====");System.out.println("1. 修改登录密码");System.out.println("2. 查看自己所上课程");System.out.println("3. 选修课选课");System.out.println("0. 退出");System.out.print("请选择操作：");}@Overridepublic void operate() {Scanner scanner = new Scanner(System.in);while (true) {displayMenu();int choice = scanner.nextInt();scanner.nextLine(); // 消耗换行符switch (choice) {case 1:changePassword(scanner); // 传递 Scanner 对象break;case 2:viewCoursesEnrolled();break;case 3:selectElectiveCourse();break;case 0:System.out.println("退出学生系统。");return;default:System.out.println("无效的选择，请重新输入。");}}}public void changePassword(Scanner scanner) { // 接受 Scanner 作为参数System.out.print("请输入新密码：");String newPassword = scanner.nextLine();super.changePassword(newPassword); // 调用父类的方法}public void viewCoursesEnrolled() {System.out.println("===== 已选课程列表 =====");for (Course course : coursesEnrolled) {System.out.println(course);}}public void selectElectiveCourse() {Scanner scanner = new Scanner(System.in);System.out.print("请输入选修课ID：");String courseID = scanner.nextLine();Course course = findCourseByID(courseID);if (course == null) {System.out.println("课程不存在！");return;}if (!(course instanceof ElectiveCourse)) {System.out.println("这不是一门选修课！");return;}ElectiveCourse electiveCourse = (ElectiveCourse) course;if (electiveCourse.getNumberOfStudents() >= electiveCourse.getMaxStudents()) {System.out.println("选课人数已满！");return;}if (coursesEnrolled.contains(course)) {System.out.println("您已选过此课程！");return;}coursesEnrolled.add(course);course.incrementStudentNumber();System.out.println("选课成功！");}private Course findCourseByID(String courseID) {for (Course course : Main.courseList) {if (course.getCourseID().equals(courseID)) {return course;}}return null;}public List<Course> getCoursesEnrolled() {return coursesEnrolled;}
}

Teacher.java

package experiment_4;import java.util.*;public class Student extends User {private List<Course> coursesEnrolled;public Student(String username) {super(username);this.coursesEnrolled = new ArrayList<>();}@Overridepublic void displayMenu() {System.out.println("===== 学生菜单 =====");System.out.println("1. 修改登录密码");System.out.println("2. 查看自己所上课程");System.out.println("3. 选修课选课");System.out.println("0. 退出");System.out.print("请选择操作：");}@Overridepublic void operate() {Scanner scanner = new Scanner(System.in);while (true) {displayMenu();int choice = scanner.nextInt();scanner.nextLine(); // 消耗换行符switch (choice) {case 1:changePassword(scanner); // 传递 Scanner 对象break;case 2:viewCoursesEnrolled();break;case 3:selectElectiveCourse();break;case 0:System.out.println("退出学生系统。");return;default:System.out.println("无效的选择，请重新输入。");}}}public void changePassword(Scanner scanner) { // 接受 Scanner 作为参数System.out.print("请输入新密码：");String newPassword = scanner.nextLine();super.changePassword(newPassword); // 调用父类的方法}public void viewCoursesEnrolled() {System.out.println("===== 已选课程列表 =====");for (Course course : coursesEnrolled) {System.out.println(course);}}public void selectElectiveCourse() {Scanner scanner = new Scanner(System.in);System.out.print("请输入选修课ID：");String courseID = scanner.nextLine();Course course = findCourseByID(courseID);if (course == null) {System.out.println("课程不存在！");return;}if (!(course instanceof ElectiveCourse)) {System.out.println("这不是一门选修课！");return;}ElectiveCourse electiveCourse = (ElectiveCourse) course;if (electiveCourse.getNumberOfStudents() >= electiveCourse.getMaxStudents()) {System.out.println("选课人数已满！");return;}if (coursesEnrolled.contains(course)) {System.out.println("您已选过此课程！");return;}coursesEnrolled.add(course);course.incrementStudentNumber();System.out.println("选课成功！");}private Course findCourseByID(String courseID) {for (Course course : Main.courseList) {if (course.getCourseID().equals(courseID)) {return course;}}return null;}public List<Course> getCoursesEnrolled() {return coursesEnrolled;}
}

User.java

package experiment_4;import java.io.Serializable;//允许类的对象可以被序列化public abstract class User implements Serializable {protected String username;protected String password;//在定义该成员的类内部、同一包中的其他类、以及任何子类中（无论子类是否在同一个包中）都可以访问。public User(String username) {this.username = username;this.password = "123456"; // 初始密码}public String getUsername() {return username;}public void setPassword(String newPassword) {//设置密码this.password = newPassword;}public boolean verifyPassword(String password) {//验证密码return this.password.equals(password);}public void changePassword(String newPassword) {//修改密码this.password = newPassword;System.out.println("密码修改成功！");}public abstract void displayMenu();public abstract void operate();
}

无需用到模块化module-info.java

/*** */
/*** */
module experiment_4 {
}