Map에 List 넣기(JAVA)

# Map With List

source) MapWithList.java

package com.source.map;
 
package com.source.map;
 
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
 
public class MapWithList {
    public static void main(String[] args) {
        List list_01 = new ArrayList<Object>();
        List list_02 = new ArrayList<Object>();
        Map<String, Object> map_01 = new HashMap<String, Object>();
        Map<String, Object> map_02 = new HashMap<String, Object>();
        Map<String, Object> map_03 = new HashMap<String, Object>();
        
        // Map에 Data를 넣은 뒤 List에 담는 로직 (S)
        map_01.put("key_01", "value_01");
        map_01.put("key_02", "value_02");
        list_01.add(map_01);
        
        map_02.put("key_03", "value_03");
        map_02.put("key_04", "value_04");
        list_02.add(map_02);
        // Map에 Data를 넣은 뒤 List에 담는 로직 (E)
        
        // Map에 List를 담는 로직 (S)
        map_03.put("firstList", list_01);
        map_03.put("secondList", list_02);
        // Map에 List를 담는 로직 (E)
        
        showContents(map_03);
        
    }
    
    public static void showContents(Map<String, Object> mapReceiver) {
        List list_01 = new ArrayList<Object>();
        List list_02 = new ArrayList<Object>();
        Map<String, Object> map_01 = new HashMap<String, Object>();
        Map<String, Object> map_02 = new HashMap<String, Object>();
        
        list_01 = (List) mapReceiver.get("firstList");
        list_02 = (List) mapReceiver.get("secondList");
        map_01 = (Map<String, Object>) list_01.get(0);
        map_02 = (Map<String, Object>) list_02.get(0);
        
        System.out.println(map_01);
        System.out.println(map_02);
        
        System.out.println(map_01.get("key_01"));
        System.out.println(map_01.get("key_02"));
        
        System.out.println(map_02.get("key_03"));
        System.out.println(map_02.get("key_04"));
    }
}
 

result)

{key_02=value_02, key_01=value_01}
{key_04=value_04, key_03=value_03}
value_01
value_02
value_03
value_04