List中放Map的几种方式

Posted 2021-11-04 xianyao

package Test;

import java.util.*;

public class Test {
    public static void main(String[] args) {

//第一种：直接加入
        List<Map<String, Object>> list1 = new ArrayList<Map<String, Object>>();
        Map<String, Object> m1 = new HashMap<String, Object>();
        m1.put("age", "55");
        m1.put("name", "66");
        list1.add(m1);
        System.out.println(list1);
//[{name=66, age=55}]

//第二种：直接插入，但是key永远只对应一个value
        List<Map<String, Object>> list2 = new ArrayList<Map<String, Object>>();
        Map<String, Object> m = new HashMap<String, Object>();
        m.put("age", "55");
        m.put("name", "66");
        list2.add(m);
        for (Map<String, Object> m2 : list2) {
            m2.put("key", "123");
        }
        System.out.println(list2);
//[{name=66, age=55, key=123}]

//第三种:能插入多个值，就是一个key能对应多个value
        List<Map<String, Object>> list3 = new ArrayList<Map<String, Object>>();
        Map<String, Object> m3 = new HashMap<String, Object>();
        m3.put("age", "55");
        m3.put("name", "66");
        for (int i = 0; i < 2; i++) {
            Map<String, Object> mm = new HashMap<String, Object>();
            mm.putAll(m3);
            mm.put("key1", i);
            list3.add(mm);
        }
        System.out.println(list3);
//[{name=66, key1=0, age=55}, {name=66, key1=1, age=55}]

    }

}