Main.java

// 主类，用于测试学生管理系统
public class Main {
    public static void main(String[] args) {
        StudentManagementSystem sms = new StudentManagementSystem();

        // 添加学生
        sms.addStudent(new Student(1, "Alice", 20));
        sms.addStudent(new Student(2, "Bob", 21));

        // 显示所有学生
        System.out.println("所有学生信息：");
        sms.displayAllStudents();

        // 根据 ID 查询学生
        Student foundStudent = sms.findStudentById(1);
        if (foundStudent != null) {
            System.out.println("找到学生：" + foundStudent);
        } else {
            System.out.println("未找到该学生");
        }

        // 删除学生
        sms.removeStudent(2);
        System.out.println("删除 ID 为 2 的学生后，剩余学生信息：");
        sms.displayAllStudents();
    }
}    

Student.java

// 定义学生类
class Student {
    private int id;
    private String name;
    private int age;

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

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public String toString() {
        return "Student{id=" + id + ", name='" + name + "', age=" + age + "}";
    }
}    

StudentManagementSystem.java

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

// 定义学生管理系统类
class StudentManagementSystem {
    private List<Student> students;

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

    // 添加学生
    public void addStudent(Student student) {
        students.add(student);
    }

    // 删除学生
    public void removeStudent(int id) {
        students.removeIf(student -> student.getId() == id);
    }

    // 根据 ID 查询学生
    public Student findStudentById(int id) {
        for (Student student : students) {
            if (student.getId() == id) {
                return student;
            }
        }
        return null;
    }

    // 显示所有学生
    public void displayAllStudents() {
        for (Student student : students) {
            System.out.println(student);
        }
    }
}