Java で簡単な学生アクティビティ登録システムを設計するにはどうすればよいですか?

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

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

    // getter和setter方法

    // 其他操作方法，如打印学生信息等
}

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

public class StudentManager {
    private List<Student> studentList;

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

    public void addStudent(Student student) {
        studentList.add(student);
    }

    public void deleteStudent(int id) {
        for (Student student : studentList) {
            if (student.getId() == id) {
                studentList.remove(student);
                break;
            }
        }
    }

    public void updateStudent(int id, Student newStudent) {
        for (int i = 0; i < studentList.size(); i++) {
            if (studentList.get(i).getId() == id) {
                studentList.set(i, newStudent);
                break;
            }
        }
    }

    // 其他操作方法，如根据学号查询学生信息等
}

public class Test {
    public static void main(String[] args) {
        Student student1 = new Student(1, "Tom", 1);
        Student student2 = new Student(2, "Jerry", 2);

        StudentManager studentManager = new StudentManager();
        studentManager.addStudent(student1);
        studentManager.addStudent(student2);

        studentManager.deleteStudent(1);

        Activity activity = new Activity("Basketball", "2022-01-01", "Gym");

        ActivityManager activityManager = new ActivityManager();
        activityManager.addActivity(activity);

        Enrollment enrollment = new Enrollment(student2, activity);

        EnrollmentManager enrollmentManager = new EnrollmentManager();
        enrollmentManager.addEnrollment(enrollment);

        // 其他操作和测试代码
    }
}