Java学习Map之案例：HashMap集合存储学生对象并遍历

需求：创建一个HashMap集合，键是学号（String），值是学生对象(Student)。存储三个键值对元素，并遍历

1.定义学生类

2.创建HashMap集合对象

3.创建学生对象

4.把学生添加到集合

5.遍历集合

    方式1:键值找

    方式2:键值对对象找键和值

package com.itheima_25;

import java.util.HashMap;
import java.util.Map;
import java.util.Set;

/*
   需求：创建一个HashMap集合，键是学号（String），值是学生对象(Student)。存储三个键值对元素，并遍历
1.定义学生类
2.创建HashMap集合对象
3.创建学生对象
4.把学生添加到集合
5.遍历集合
    方式1:键值找
    方式2:键值对对象找键和值
 */
public class HashMapDemo {
    public static void main(String[] args) {
        //创建HashMap集合对象
        HashMap<String,Student>  hm = new HashMap<String,Student>();
        //创建学生对象
        Student s1 = new Student("张三",20);
        Student s2 = new Student("李四",22);
        Student s3 = new Student("王五",23);
        Student s4 = new Student("赵六",24);

        //把学生添加到集合
        hm.put("wx001",s1);
        hm.put("wx002",s2);
        hm.put("wx003",s3);
        hm.put("wx004",s4);

        //方式1:键找值
        Set<String> keySet = hm.keySet();
        for(String key:keySet){
            Student value = hm.get(key);
            System.out.println(key + "," + value.getName() + "," + value.getAge());

        }
        System.out.println("-----------------------------------------------------");
        //方式2:键值对对象找键和值
        Set<Map.Entry<String, Student>> entries = hm.entrySet();

        for (Map.Entry<String, Student> entry:entries){
            String key = entry.getKey();
            Student value = entry.getValue();
            System.out.println(key + "," + value.getName() + "," + value.getAge());
        }

    }
}

package com.itheima_25;

public class Student {
    private String name;
    private int age;


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

    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;
    }
}