// 学生数据模型 - Model层
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class StudentModel {
    private Map<String, Student> students = new HashMap<>();

    // 添加学生
    public boolean addStudent(Student student) {
        if (students.containsKey(student.getId())) {
            return false; // 学生ID已存在
        }
        students.put(student.getId(), student);
        return true;
    }

    // 删除学生
    public boolean deleteStudent(String id) {
        if (!students.containsKey(id)) {
            return false;
        }
        students.remove(id);
        return true;
    }

    // 更新学生信息
    public boolean updateStudent(Student student) {
        if (!students.containsKey(student.getId())) {
            return false;
        }
        students.put(student.getId(), student);
        return true;
    }

    // 查找学生
    public Student findStudent(String id) {
        return students.get(id);
    }

    // 获取所有学生
    public List<Student> getAllStudents() {
        return new ArrayList<>(students.values());
    }
}