Java-集合框架-map4（嵌套集合）

package cn.burce.HashMap;

import java.util.HashMap;

public class MapDemo3 {
    // 神奇小学
    // 一年级
    // 101 小米 102 小明
    // 二年级
    // 201 大米 202 大明
    public static void main(String[] args) {
        fun();
        System.out.println("----------------------------------");
        fun1();
    }

    public static void fun() {
        HashMap<String, String> one = new HashMap<>();
        HashMap<String, String> two = new HashMap<>();
        one.put("101", "小米");
        one.put("102", "小明");
        two.put("201", "大米");
        two.put("202", "大明");
        HashMap<String, HashMap<String, String>> school = new HashMap<>();
        school.put("一年级", one);
        school.put("二年级", two);
        System.out.println(school + "大大主键");
        Set<String> set = new HashSet<>();
        set = school.keySet();// 将键存到set集合，键是一个String
        Iterator<String> it = set.iterator();// 通过Iterator去遍历这组字符串
        while (it.hasNext())
        {
            String str = it.next();
            System.out.println(str + "大主键");
            HashMap<String, String> p1 = school.get(str);
            System.out.println(p1 + "嵌套集合");
            Set<String> set1 = p1.keySet();// 将键存到set集合，键是一个String
            System.out.println("set1是"+set1);
            // 增强for
            for (String s : set1)
            {
                System.out.println(str+"..."+s+"..."+p1.get(s));
            }
        }
    }

    public static void fun1() {
        HashMap<String, String> thr = new HashMap<>();
        HashMap<String, String> four = new HashMap<>();
        thr.put("301", "豪情天下");
        thr.put("302", "光阴似箭");
        four.put("401", "龙腾万里");
        four.put("402", "无印之水");
        HashMap<String, HashMap<String, String>> school = new HashMap<>();
        school.put("三年级", thr);
        school.put("四年级", four);
        System.out.println(school + "大大主键");
        // 将map中的方法 entrySet取出映射关系，存到Set集合里Set<K,V>
        Set<Map.Entry<String, HashMap<String, String>>> set = school.entrySet();
        Iterator<Map.Entry<String, HashMap<String, String>>> it = set.iterator();
        while (it.hasNext())
        {// 获取出set集合的元素，这里仍旧是map结构
            Map.Entry<String, HashMap<String, String>> entry = it.next();
            // 根据getKey和getValue取出键值
            String s = entry.getKey();
            // System.out.println(s);
            HashMap<String, String> zclass = entry.getValue();
            Set<Map.Entry<String, String>> set1 = zclass.entrySet();
            // 增强for
            for (Map.Entry<String, String> entry2 : set1)
            {
                System.out.println(s + "..." + entry2.getKey() + "..." + entry2.getValue());
            }
        }
    }
}

实际上也就是多重的集合取数