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集合嵌套案例分析

代码：

package com.itheima.day27_Collection_nesting;import java.util.*;/*目标:理解集合的嵌套。
江苏省 ="南京市","扬州市","苏州市","无锡市","常州市"
湖北省 ="武汉市","孝感市","十堰市","宜昌市","鄂州市"
河北省 ="石家庄市","唐山市","邢台市","保定市","张家口市"
*/
public class CollectionNestingTest {public static void main(String[] args) {// 1、定义一个Map集合存储全部的省份信息，和其对应的城市信息。Map<String, List<String>> map= new HashMap<>();List<String> cities1 = new ArrayList<>();Collections.addAll(cities1,"南京市","扬州市","苏州市","无锡市","常州市");map.put("江苏省",cities1);List<String> cities2 = new ArrayList<>();Collections.addAll(cities2,"武汉市","孝感市","十堰市","宜昌市","鄂州市");map.put("湖北省",cities2);List<String> cities3 = new ArrayList<>();Collections.addAll(cities3,"石家庄市","唐山市","邢台市","保定市","张家口市");map.put("河北省",cities3);System.out.println(map);List<String> citis = map.get("湖北省");for (String citi : citis) {System.out.println(citi);}map.forEach((p,c)->{System.out.println(p+"--------->"+c);});}
}