编写一段学生管理系统的代码

好的，以下是一个简单的学生管理系统的代码示例，仅供参考：

import java.util.ArrayList;
import java.util.Scanner;

public class StudentManagementSystem {
    private ArrayList<Student> students;

    public StudentManagementSystem() {
        students = new ArrayList<Student>();
    }

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

    public void removeStudent(int index) {
        students.remove(index);
    }

    public void displayAllStudents() {
        for (Student student: students) {
            System.out.println(student.toString());
        }
    }

    public void displayStudent(int index) {
        System.out.println(students.get(index).toString());
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        StudentManagementSystem sms = new StudentManagementSystem();

        boolean exit = false;
        while (!exit) {
            System.out.println("1. Add student\n2. Remove student\n3. Display all students\n4. Display student\n5. Exit");
            System.out.print("Enter your choice: ");
            int choice = scanner.nextInt();

            switch (choice) {
                case 1:
                    System.out.print("Enter student name: ");
                    String name = scanner.next();
                    System.out.print("Enter student age: ");
                    int age = scanner.nextInt();
                    System.out.print("Enter student grade: ");
                    int grade = scanner.nextInt();
                    sms.addStudent(new Student(name, age, grade));
                    break;
                case 2:
                    System.out.print("Enter student index to remove: ");
                    int index = scanner.nextInt();
                    sms.removeStudent(index);
                    break;
                case 3:
                    sms.displayAllStudents();
                    break;
                case 4:
                    System.out.print("Enter student index to display: ");
                    index = scanner.nextInt();
                    sms.displayStudent(index);
                    break;
                case 5:
                    exit = true;
                    break;
                default:
                    System.out.println("Invalid choice. Please try again.");
            }
        }

        scanner.close();
    }
}

class Student {
    private String name;
    private int age;
    private int grade;

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

    public String toString() {
        return "Name: " + name + "\nAge: " + age + "\nGrade: " + grade;
    }
}

该示例代码实现了一个简单的学生管理系统，可以添加、删除、显示所有学生和显示单个学生。它使用了一个 `Student` 类来表示学生，`StudentManagementSystem` 类来管理学生，以及一个主方法来处理用户输入和调用相应的方法。