// 定义学生类 
class Student { 
    private String name; 
    private int age; 
    private String gender; 
    private String id; 
 
    // 构造函数 
    public Student(String name, int age, String gender, String id) { 
        this.name = name; 
        this.age = age; 
        this.gender = gender; 
        this.id = id; 
    } 
 
    // getter和setter方法 
    public String getName() { 
        return name; 
    } 
 
    public void setName(String name) { 
        this.name = name; 
    } 
 
    public int getAge() { 
        return age; 
    } 
 
    public void setAge(int age) { 
        this.age = age; 
    } 
 
    public String getGender() { 
        return gender; 
    } 
 
    public void setGender(String gender) { 
        this.gender = gender; 
    } 
 
    public String getId() { 
        return id; 
    } 
 
    public void setId(String id) { 
        this.id = id; 
    } 
} 
 
// 定义学生管理系统类 
class StudentManagementSystem { 
    private List
  
    students; 
 
    // 构造函数 
    public StudentManagementSystem() { 
        students = new ArrayList<>(); 
    } 
 
    // 添加学生 
    public void addStudent(Student student) { 
        students.add(student); 
    } 
 
    // 删除学生 
    public void deleteStudent(String id) { 
        for (Student student : students) { 
            if (student.getId().equals(id)) { 
                students.remove(student); 
                break; 
            } 
        } 
    } 
 
    // 修改学生信息 
    public void updateStudent(String id, String name, int age, String gender) { 
        for (Student student : students) { 
            if (student.getId().equals(id)) { 
                student.setName(name); 
                student.setAge(age); 
                student.setGender(gender); 
                break; 
            } 
        } 
    } 
 
    // 查询学生信息 
    public Student queryStudent(String id) { 
        for (Student student : students) { 
            if (student.getId().equals(id)) { 
                return student; 
            } 
        } 
        return null; 
    } 
} 
 
// 测试学生管理系统 
public class TestStudentManagementSystem { 
    public static void main(String[] args) { 
        StudentManagementSystem sms = new StudentManagementSystem(); 
 
        // 添加学生 
        sms.addStudent(new Student("张三", 18, "男", "001")); 
        sms.addStudent(new Student("李四", 19, "女", "002")); 
        sms.addStudent(new Student("王五", 20, "男", "003")); 
 
        // 查询学生信息 
        Student student = sms.queryStudent("002"); 
        System.out.println(student.getName() + " " + student.getAge() + " " + student.getGender()); 
 
        // 修改学生信息 
        sms.updateStudent("002", "赵六", 21, "男"); 
 
        // 删除学生 
        sms.deleteStudent("003"); 
    } 
}