编写Java程序，使用List集合和Map集合输出 市和区

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class Test1 {
    public static void main(String[] args) {
      //云南省的 - 市
      ArrayList<String> ynCity = new ArrayList<>();
      ynCity.add("昆明市");
      ynCity.add("昭通市");
      ynCity.add("大理市");
      ynCity.add("丽江市");
      //湖南省的 - 市
      ArrayList<String> hnCity = new ArrayList<>();
      hnCity.add("长沙市");
      hnCity.add("岳阳市");
      hnCity.add("常德市");
      hnCity.add("永州市");
      //将市 和 区 存入Map集合
      HashMap<String, ArrayList<String>> provinceCity = new HashMap<String, ArrayList<String>>();
      provinceCity.put("云南省",ynCity);
      provinceCity.put("湖南省",hnCity);
      //将省和市存入countries Map集合中
      HashMap<String, HashMap<String,ArrayList<String>>> countries = new HashMap<String,HashMap<String,ArrayList<String>>>();
      countries.put("中国",provinceCity);
//      countries.put("美国",provinceCity);//这里只写了中国的省和市这行注释掉
      Set<String> countriesMapkey = countries.keySet();//得到Map 集合 countries的键 存入countriesMapkey中
      Iterator it1 = countriesMapkey.iterator();//用键创建一个迭代器
      while (it1.hasNext()) {
        Object countriesMapkeys = it1.next();//遍历得到键集合存入countriesMapkeys
        System.out.println(countriesMapkeys);
        HashMap<String, ArrayList<String>> countriesMapValue = countries.get(countriesMapkeys);//得到键集合对应的值存入countriesMapValue
        Set<String> provinceCityMapKey = countriesMapValue.keySet();//得到Map集合中provinceCity的键
        Iterator it2 =  provinceCityMapKey.iterator();//创建一个迭代器
        while (it2.hasNext()) {
          Object provinceCityMapKeys = it2.next();//得到Map 集合 provinceCity的键 存入countriesMapkey中
          System.out.println("    "+provinceCityMapKeys);
          ArrayList<String> provinceCityValue = provinceCity.get(provinceCityMapKeys);//得到provinceCity的键对应的值集合
          for (int i = 0; i < provinceCityValue.size(); i++) {
            System.out.println("        "+provinceCityValue.get(i));//循环输出provinceCity的值
          }
        }
      }
    }
}