用java设计一个教材类，一个课程类，及一个为某门课程指定参考教材的类。一门课程可以有多本参考教材，再设计一个测试类。 设计一个简单的学生选课系统，并可以完成添加、删除、修改、查询相关信息 。 说明：设计以下类： 描述课程基本信息类(课程编号，课程名，学分 )； 描述学生基本信息类(学号，姓名，专业方向 )； 记录选课结果的类(课程，选课的学生，课程最多人数，当前人数 )； 测试类(设定或输入最多人数，创建课程对象，创建选课学生对象，创建选课对象，显示选课情况 )可以在idea中运行。

好的，我会根据您的要求设计这些类。首先是教材类：

public class Textbook {
    private String name;
    private String author;
    private double price;

    public Textbook(String name, String author, double price) {
        this.name = name;
        this.author = author;
        this.price = price;
    }

    // Getters and setters
    public String getName() {
        return name;
    }

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

    public String getAuthor() {
        return author;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

接下来是课程类：

import java.util.ArrayList;

public class Course {
    private String code;
    private String name;
    private int credit;
    private ArrayList<Textbook> textbooks;

    public Course(String code, String name, int credit) {
        this.code = code;
        this.name = name;
        this.credit = credit;
        this.textbooks = new ArrayList<>();
    }

    public void addTextbook(Textbook textbook) {
        textbooks.add(textbook);
    }

    // Getters and setters
    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    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 ArrayList<Textbook> getTextbooks() {
        return textbooks;
    }

    public void setTextbooks(ArrayList<Textbook> textbooks) {
        this.textbooks = textbooks;
    }
}

然后是为某门课程指定参考教材的类：

public class CourseTextbook {
    private Course course;
    private Textbook textbook;

    public CourseTextbook(Course course, Textbook textbook) {
        this.course = course;
        this.textbook = textbook;
        course.addTextbook(textbook);
    }

    // Getters and setters
    public Course getCourse() {
        return course;
    }

    public void setCourse(Course course) {
        this.course = course;
    }

    public Textbook getTextbook() {
        return textbook;
    }

    public void setTextbook(Textbook textbook) {
        this.textbook = textbook;
    }
}

下面是描述学生基本信息类：

public class Student {
    private String id;
    private String name;
    private String major;

    public Student(String id, String name, String major) {
        this.id = id;
        this.name = name;
        this.major = major;
    }

    // Getters and setters
    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }
}

然后是记录选课结果的类：

import java.util.ArrayList;

public class Enrollment {
    private Course course;
    private int maxStudents;
    private ArrayList<Student> students;

    public Enrollment(Course course, int maxStudents) {
        this.course = course;
        this.maxStudents = maxStudents;
        this.students = new ArrayList<>();
    }

    public boolean addStudent(Student student) {
        if (students.size() < maxStudents) {
            students.add(student);
            return true;
        }
        return false;
    }

    public boolean removeStudent(Student student) {
        return students.remove(student);
    }

    // Getters and setters
    public Course getCourse() {
        return course;
    }

    public void setCourse(Course course) {
        this.course = course;
    }

    public int getMaxStudents() {
        return maxStudents;
    }

    public void setMaxStudents(int maxStudents) {
        this.maxStudents = maxStudents;
    }

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

    public void setStudents(ArrayList<Student> students) {
        this.students = students;
    }
}

最后是测试类：

import java.util.ArrayList;

public class Test {
    public static void main(String[] args) {
        // 设定最多人数
        int maxStudents = 50;

        // 创建课程对象
        Course math = new Course("MATH101", "Calculus", 3);
        Course physics = new Course("PHYS101", "Mechanics", 4);

        // 创建教材对象
        Textbook mathTextbook1 = new Textbook("Calculus, 10th edition", "Ron Larson, Bruce H. Edwards", 100.0);
        Textbook mathTextbook2 = new Textbook("Calculus, 11th edition", "Ron Larson, Bruce H. Edwards", 120.0);
        Textbook physicsTextbook1 = new Textbook("Classical Mechanics, 3rd edition", "Herbert Goldstein", 150.0);

        // 为课程指定参考教材
        CourseTextbook ct1 = new CourseTextbook(math, mathTextbook1);
        CourseTextbook ct2 = new CourseTextbook(math, mathTextbook2);
        CourseTextbook ct3 = new CourseTextbook(physics, physicsTextbook1);

        // 创建学生对象
        Student s1 = new Student("101", "Tom", "Mathematics");
        Student s2 = new Student("102", "Jerry", "Physics");
        Student s3 = new Student("103", "Lucy", "Mathematics");

        // 创建选课对象
        Enrollment mathEnrollment = new Enrollment(math, maxStudents);
        Enrollment physicsEnrollment = new Enrollment(physics, maxStudents);

        // 添加学生到选课对象中
        mathEnrollment.addStudent(s1);
        mathEnrollment.addStudent(s3);
        physicsEnrollment.addStudent(s2);

        // 显示选课情况
        System.out.println("Math enrollment: " + mathEnrollment.getStudents().size() + "/" + mathEnrollment.getMaxStudents());
        for (Student student : mathEnrollment.getStudents()) {
            System.out.println(student.getName());
        }

        System.out.println("Physics enrollment: " + physicsEnrollment.getStudents().size() + "/" + physicsEnrollment.getMaxStudents());
        for (Student student : physicsEnrollment.getStudents()) {
            System.out.println(student.getName());
        }
    }
}

这个简单的学生选课系统可以实现添加、删除、修改、查询相关信息。您可以根据自己的需求进行扩展。