java集合的运用，把数组和对象的json格式，转换成对象和数组的格式

朱雀 2022-06-02 09:29 140阅读 0赞

package com.yanshu.utils;  
  
  
import java.util.ArrayList;  
import java.util.HashMap;  
import java.util.List;  
import java.util.Map;  
import java.util.Set;  
  
  
import org.jboss.jandex.Main;  
  
  
import com.alibaba.fastjson.JSON;  
  
  
public class MapUtil \{  
  
  
public static String ListTojson(List<HashMap> map2)\{  
if(map2.size()==0)\{  
return "\{\}";  
\}  
Map<String,List> map=new HashMap<String,List>();  
Set<String> set=map2.get(0).keySet();  
for (String setchild : set) \{  
map.put(setchild, new ArrayList<>());  
\}  
  
  
for (int i = 0; i < map2.size(); i++) \{  
for (String str : set) \{  
map.get(str).add(map2.get(i).get(str)==null?0:map2.get(i).get(str));  
\}  
\}  
return   JSON.toJSONString(map);  
\}  
  
public static String  ListTurnMap(List<HashMap> maps)  
\{  
//如何长度等于0,返回空  
if(maps.size()==0)  
\{  
return "\{\}";  
\}  
Map<String,List> map=new HashMap<>();  
Set<String> set=maps.get(0).keySet();//获取List<HashMap> maps的第一个键  
System.out.println("set--->>>"+set);  
for (String setchild : set) \{  
map.put(setchild,new ArrayList<>());//\[\{tom=23, mary=12\}, \{tom=33, mary=22\}\]转换成\{tom=\[\], mary=\[\]\}  
\}  
System.out.println("map-->>"+map);  
//填值  
for(int i=0;i<maps.size();i++)  
\{  
for (String str : set) \{  
//map.get(str).add(map2.get(i).get(str)==null?0:map2.get(i).get(str));  
map.get(str).add(maps.get(i).get(str)==null?0:maps.get(i).get(str));  
  
\}  
\}  
  
  
  
return   JSON.toJSONString(map);//\{"tom":\[23,33\],"mary":\[12,22\]\}  
  
\}  
  
public static void main(String\[\] args) \{  
Map map1=new HashMap<>();  
Map map2=new HashMap<>();  
map1.put("tom",23);  
map1.put("mary",12);  
map2.put("tom",33);  
map2.put("mary",22);  
List list=new ArrayList();  
list.add(map1);  
list.add(map2);  
System.out.println(list);  
String listTojson = ListTurnMap(list);  
  
System.out.println(listTojson);  
  
  
  
  
  
  
\}  
\}