实验18：迭代器模式

本次实验属于模仿型实验，通过本次实验学生将掌握以下内容： 

1、理解迭代器模式的动机，掌握该模式的结构；

2、能够利用迭代器模式解决实际问题。

[实验任务]：JAVA和C++常见数据结构迭代器的使用

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。

实验要求：

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；

代码

import java.util.*;

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

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

public class List_Iterator
{
    public static void sortById(List list)
    {
        Iterator<Student> sIterator = list.iterator();
        while (sIterator.hasNext())
        {
            Student student = sIterator.next();
            System.out.println("学号: " + student.id + ", 姓名: " + student.name + ", 年龄: " + student.age);
        }
    }

    public static void main(String[] args)
    {
        List<Student> studentList = new ArrayList<>();
        studentList.add(new Student(20213971, "门殿宇", 20));
        studentList.add(new Student(20211234, "张三", 20));
        studentList.add(new Student(20214352, "李四", 20));
        studentList.add(new Student(20210123, "王五", 20));
        studentList.add(new Student(20214444, "小明", 20));
        studentList.add(new Student(20215423, "小李", 20));
        studentList.add(new Student(20217462, "小王", 20));
        studentList.add(new Student(20212344, "小张", 20));
        studentList.add(new Student(20213888, "小刘", 20));
        studentList.add(new Student(20219999, "小马", 20));


        //按学号升序排序
        Collections.sort(studentList, Comparator.comparingInt(student -> student.id));

        //用迭代器打印
        System.out.println("按学号升序:");
        sortById(studentList);


        Collections.reverse(studentList);
        //迭代器打印降序学号
        System.out.println("\n按学号降序:");
        sortById(studentList);
    }
}

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

using namespace std;

// 自定义数据类型
class Student
{
public:
    int id;
    string name;
    int age;

public:
    Student(int id, string name, int age) : id(id), name(name), age(age)
    {}
};

// 比较函数，按学号升序排序
bool compareByIdUp(const Student &a, const Student &b)
{
    return a.id < b.id;
}

//按学号降序排序
bool compareByIdDown(const Student &a, const Student &b)
{
    return a.id > b.id;
}

// 打印学生信息
void printStudentInfo(vector<Student> &v)
{
    for (vector<Student>::iterator it = v.begin(); it != v.end(); it++)
    {
        cout << "学号:" << (*it).id << "  姓名:" << (*it).name << "  年龄:" << (*it).age << endl;
    }
    cout << endl;
}

int main()
{
    vector<Student> students;
    students.emplace_back(20213971, "门殿宇", 20);
    students.emplace_back(20211234, "张三", 20);
    students.emplace_back(20214352, "李四", 20);
    students.emplace_back(20210123, "王五", 20);
    students.emplace_back(20214444, "小明", 20);
    students.emplace_back(20215423, "小李", 20);
    students.emplace_back(20217462, "小王", 20);
    students.emplace_back(20212344, "小张", 20);
    students.emplace_back(20213888, "小刘", 20);
    students.emplace_back(20219999, "小马", 20);

    // 使用 sort 函数和比较函数按学号升序排序
    sort(students.begin(), students.end(), compareByIdUp);

    cout << "按学号升序排列" << endl;
    // 打印排序后的学生信息
    printStudentInfo(students);


    // 使用 sort 函数和比较函数按学号降序排序
    sort(students.begin(), students.end(), compareByIdDown);

    cout << "按学号降序排列" << endl;
    // 打印排序后的学生信息
    printStudentInfo(students);

    return 0;
}

 运行效果