264 集合嵌套之ArrayList嵌套hashmap

264 集合嵌套之ArrayList嵌套hashmap

看起来很复杂的样子？——还好

【需求】

创建一个ArrayList集合，存储3个元素，每个元素都是HashMap，

HashMap的键、值是String，并遍历

【思路】

1. 创建ArrayList集合

2. 创建HashMap集合，并添加键值对元素

3. 添加HashMap到ArrayList集合

4. 遍历ArrayList集合

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package e264;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Set;

public class ArrayListDemo {

    public static void main(String[] args) {

        ArrayList> ar = new ArrayList>();

        HashMap hmhm1 = new HashMap();

        hmhm1.put("ICHIGO", "RUKIA");

        hmhm1.put("GIN", "RANGIKU");

        HashMap hmhm2 = new HashMap();

        hmhm2.put("NARUTO", "HINATA");

        hmhm2.put("SASUKE", "SAKURA");

        HashMap hmhm3 = new HashMap();

        hmhm3.put("ROSS", "RACHEL");

        hmhm3.put("CHANDLER", "MONICA");

        ar.add(hmhm1);

        ar.add(hmhm2);

        ar.add(hmhm3);

        System.out.println(ar);//[{ICHIGO=RUKIA, GIN=RANGIKU}, {NARUTO=HINATA, SASUKE=SAKURA}, {CHANDLER=MONICA, ROSS=RACHEL}]

        for (HashMap hmm : ar) {

            //遍历嵌套的集合时，需要分2步：

            //-1-遍历内部集合

            //-2-遍历外部集合

            Set jianjihe = hmm.keySet();

            for (String jian : jianjihe) {

                String zhi = hmm.get(jian);

                System.out.println(jian + "," + zhi);

            }

        }

    }

}