迭代器模式

信1305班共44名同学，每名同学都有姓名，学号和年龄等属性，分别使用JAVA内置迭代器和C++中标准模板库（STL）实现对同学信息的遍历，要求按照学号从小到大和从大到小两种次序输出学生信息。

1. 搜集并掌握JAVA和C++中常见的数据结构和迭代器的使用方法，例如，vector, list, map和set等；

2. 提交源代码；

3. 注意编程规范。

Java代码：

Student.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

class Student {
    String name;
    int studentID;
    int age;

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

StudentList.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class StudentList {
    public static void main(String[] args) {
        List<Student> studentList = new ArrayList<>();

        // 从学号20213000开始生成学生对象并添加到列表，年龄都设置成20岁
        int startingStudentID = 20213000;

        for (int i = 0; i < 44; i++) {
            studentList.add(new Student("学生" + (i + 1), startingStudentID + i, 20));
        }

        // 按学号升序排序
        Collections.sort(studentList, (s1, s2) -> Integer.compare(s1.studentID, s2.studentID));

        System.out.println("按学号从小到大:");
        printStudentInfo(studentList.iterator());

        // 按学号降序排序
        Collections.sort(studentList, (s1, s2) -> Integer.compare(s2.studentID, s1.studentID));

        System.out.println("\n按学号从大到小:");
        printStudentInfo(studentList.iterator());
    }

    private static void printStudentInfo(Iterator<Student> iterator) {
        while (iterator.hasNext()) {
            Student student = iterator.next();
            System.out.println("姓名: " + student.name + "，学号: " + student.studentID + "，年龄: " + student.age);
        }
    }
}

C++

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

class Student {
public:
    std::string name;
    int studentID;
    int age;

    Student(std::string n, int id, int a) : name(n), studentID(id), age(a) {}
};

bool compareByIDAsc(const Student& s1, const Student& s2) {
    return s1.studentID < s2.studentID;
}

bool compareByIDDesc(const Student& s1, const Student& s2) {
    return s1.studentID > s2.studentID;
}

int main() {
    std::vector<Student> studentList;

    // 从学号20213000开始生成学生对象并添加到向量，年龄都设置成20岁
    int startingStudentID = 20213000;

    for (int i = 0; i < 44; i++) {
        studentList.push_back(Student("学生" + std::to_string(i + 1), startingStudentID + i, 20));
    }

    // 按学号升序排序
    std::sort(studentList.begin(), studentList.end(), compareByIDAsc);

    std::cout << "按学号从小到大:" << std::endl;
    for (const auto& student : studentList) {
        std::cout << "姓名: " << student.name << "，学号: " << student.studentID << "，年龄: " << student.age << std::endl;
    }

    // 按学号降序排序
    std::sort(studentList.begin(), studentList.end(), compareByIDDesc);

    std::cout << "\n按学号从大到小:" << std::endl;
    for (const auto& student : studentList) {
        std::cout << "姓名: " << student.name << "，学号: " << student.studentID << "，年龄: " << student.age << std::endl;
    }

    return 0;
}