在IDEA用Java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： 可以设计以下类： 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 )

好的，这是一个非常好的问题，我将尽力回答你。首先，我们需要创建三个类：Course、Student、选课结果，并且需要创建一个测试类 TestClass。

下面是每个类的详细信息：

1.描述课程基本信息类(课程编号，课程名，学分 )；

public class Course {
    private String courseId;
    private String courseName;
    private int credit;

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

    public String getCourseId() {
        return courseId;
    }

    public void setCourseId(String courseId) {
        this.courseId = courseId;
    }

    public String getCourseName() {
        return courseName;
    }

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

    public int getCredit() {
        return credit;
    }

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

2.描述学生基本信息类(学号，姓名，专业方向 )；

public class Student {
    private String studentId;
    private String studentName;
    private String major;

    public Student(String studentId, String studentName, String major) {
        this.studentId = studentId;
        this.studentName = studentName;
        this.major = major;
    }

    public String getStudentId() {
        return studentId;
    }

    public void setStudentId(String studentId) {
        this.studentId = studentId;
    }

    public String getStudentName() {
        return studentName;
    }

    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }

    public String getMajor() {
        return major;
    }

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

3.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 )；

public class CourseSelection {
    private Course course;
    private List<Student> selectedStudents;
    private int maxStudents;
    private int currentStudents;

    public CourseSelection(Course course, int maxStudents) {
        this.course = course;
        this.maxStudents = maxStudents;
        this.currentStudents = 0;
        this.selectedStudents = new ArrayList<Student>();
    }

    public boolean addStudent(Student student) {
        if (currentStudents >= maxStudents) {
            return false;
        }
        selectedStudents.add(student);
        currentStudents++;
        return true;
    }

    public boolean removeStudent(Student student) {
        boolean result = selectedStudents.remove(student);
        if (result) {
            currentStudents--;
        }
        return result;
    }

    public Course getCourse() {
        return course;
    }

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

    public List<Student> getSelectedStudents() {
        return selectedStudents;
    }

    public void setSelectedStudents(List<Student> selectedStudents) {
        this.selectedStudents = selectedStudents;
    }

    public int getMaxStudents() {
        return maxStudents;
    }

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

    public int getCurrentStudents() {
        return currentStudents;
    }

    public void setCurrentStudents(int currentStudents) {
        this.currentStudents = currentStudents;
    }
}

4.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 )

import java.util.Scanner;

public class TestClass {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入课程编号：");
        String courseId = scanner.nextLine();
        System.out.println("请输入课程名称：");
        String courseName = scanner.nextLine();
        System.out.println("请输入课程学分：");
        int credit = scanner.nextInt();
        Course course = new Course(courseId, courseName, credit);

        System.out.println("请输入最大学生人数：");
        int maxStudents = scanner.nextInt();
        CourseSelection courseSelection = new CourseSelection(course, maxStudents);

        System.out.println("请输入学生人数：");
        int studentCount = scanner.nextInt();
        scanner.nextLine();
        for (int i = 0; i < studentCount; i++) {
            System.out.println("请输入第" + (i + 1) + "个学生的学号：");
            String studentId = scanner.nextLine();
            System.out.println("请输入第" + (i + 1) + "个学生的姓名：");
            String studentName = scanner.nextLine();
            System.out.println("请输入第" + (i + 1) + "个学生的专业：");
            String major = scanner.nextLine();

            Student student = new Student(studentId, studentName, major);
            boolean result = courseSelection.addStudent(student);
            if (result) {
                System.out.println("学生" + studentName + "选课成功!");
            } else {
                System.out.println("学生" + studentName + "选课失败!");
            }
        }

        System.out.println("课程信息：");
        System.out.println("课程编号：" + course.getCourseId());
        System.out.println("课程名称：" + course.getCourseName());
        System.out.println("课程学分：" + course.getCredit());

        System.out.println("选课情况：");
        List<Student> selectedStudents = courseSelection.getSelectedStudents();
        for (int i = 0; i < selectedStudents.size(); i++) {
            Student student = selectedStudents.get(i);
            System.out.println("学生" + student.getStudentName() + "选课成功!");
        }
    }
}

这样就完成了一个简单的学生选课系统，可以完成添加、删除、修改、查询相关信息。请注意，这只是一个简单的示例，实际应用中需要更多的功能和更复杂的逻辑来实现。