Java学生选课系统实现： 1. 系统至少应包括以下信息： 学生信息：学号、姓名、性别、年级、密码 课程信息：课程编号、课程名称、已选人数、可选人数、授课教师。 2.基本功能需求： （1）使用命令行完成系统的功能设计； （2）启动程序，输出“学生选课管理——登录”。 （2）提示客户输入学号、密码。 3.其他功能需求： (1) 文件CourseDB.java：单例类，模拟数据库中的课程，初始化后至少封装10门课程； （2）文件StudentDB.java：单列类，模拟数据库中的课程，初始化后至少封装5名学生信息； （3）文件Login.java:负责登录的业务逻辑； （4）文件SelectCourse.java：负责选课的业务逻辑； （5）文件MainProcess.java：负责整体业务流程； （6）学生选课成功后，选课状态变更为“已选”，否则，课程状态变更为“可选”；学生选择“已选”课程，提示“该课程无法重复选择”； （7）学生选课成功后，选课人数相应发生变化；代码

以下是一个基本的Java学生选课系统的代码实现，包含了上述所述的所有信息和功能需求：

Course.java

public class Course {
    private int id;
    private String name;
    private int selectedNum;
    private int maxNum;
    private String teacher;

    public Course(int id, String name, int maxNum, String teacher) {
        this.id = id;
        this.name = name;
        this.maxNum = maxNum;
        this.teacher = teacher;
        this.selectedNum = 0;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getSelectedNum() {
        return selectedNum;
    }

    public int getMaxNum() {
        return maxNum;
    }

    public String getTeacher() {
        return teacher;
    }

    public boolean isSelected() {
        return selectedNum >= maxNum;
    }

    public void select() {
        selectedNum++;
    }

    public void unselect() {
        selectedNum--;
    }
}

CourseDB.java

import java.util.ArrayList;
import java.util.List;

public class CourseDB {
    private static CourseDB instance = null;
    private List<Course> courses;

    private CourseDB() {
        courses = new ArrayList<Course>();
        courses.add(new Course(1, "Java Programming", 30, "Tom"));
        courses.add(new Course(2, "Data Structures", 30, "Jerry"));
        courses.add(new Course(3, "Algorithm Design", 30, "Lucy"));
        courses.add(new Course(4, "Database Systems", 30, "Lily"));
        courses.add(new Course(5, "Operating Systems", 30, "Bob"));
        courses.add(new Course(6, "Computer Networks", 30, "Alice"));
        courses.add(new Course(7, "Software Engineering", 30, "John"));
        courses.add(new Course(8, "Web Development", 30, "Mary"));
        courses.add(new Course(9, "Artificial Intelligence", 30, "David"));
        courses.add(new Course(10, "Mobile App Development", 30, "Amy"));
    }

    public static CourseDB getInstance() {
        if (instance == null) {
            instance = new CourseDB();
        }
        return instance;
    }

    public List<Course> getCourses() {
        return courses;
    }

    public Course getCourseById(int id) {
        for (Course course : courses) {
            if (course.getId() == id) {
                return course;
            }
        }
        return null;
    }
}

Student.java

public class Student {
    private int id;
    private String name;
    private String gender;
    private String grade;
    private String password;

    public Student(int id, String name, String gender, String grade, String password) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.grade = grade;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public String getGrade() {
        return grade;
    }

    public String getPassword() {
        return password;
    }
}

StudentDB.java

import java.util.ArrayList;
import java.util.List;

public class StudentDB {
    private static StudentDB instance = null;
    private List<Student> students;

    private StudentDB() {
        students = new ArrayList<Student>();
        students.add(new Student(1, "Tom", "Male", "Sophomore", "123456"));
        students.add(new Student(2, "Jerry", "Male", "Freshman", "123456"));
        students.add(new Student(3, "Lucy", "Female", "Senior", "123456"));
        students.add(new Student(4, "Lily", "Female", "Junior", "123456"));
        students.add(new Student(5, "Bob", "Male", "Senior", "123456"));
    }

    public static StudentDB getInstance() {
        if (instance == null) {
            instance = new StudentDB();
        }
        return instance;
    }

    public List<Student> getStudents() {
        return students;
    }

    public Student getStudentById(int id) {
        for (Student student : students) {
            if (student.getId() == id) {
                return student;
            }
        }
        return null;
    }
}

Login.java

import java.util.Scanner;

public class Login {
    public static Student login() {
        Scanner scanner = new Scanner(System.in);
        System.out.println("学生选课管理——登录");
        System.out.print("请输入学号：");
        int id = scanner.nextInt();
        System.out.print("请输入密码：");
        String password = scanner.next();
        StudentDB studentDB = StudentDB.getInstance();
        Student student = studentDB.getStudentById(id);
        if (student == null || !student.getPassword().equals(password)) {
            System.out.println("学号或密码错误，请重新输入！");
            return null;
        }
        return student;
    }
}

SelectCourse.java

import java.util.List;
import java.util.Scanner;

public class SelectCourse {
    private static void printCourses(List<Course> courses) {
        System.out.println("所有课程列表：");
        System.out.println("编号\t名称\t已选人数\t可选人数\t授课教师");
        for (Course course : courses) {
            System.out.printf("%d\t%s\t%d\t