（精华）将json数组和对象转换成List和Map(小龙哥和牛徳鹤的对话)

Posted 2020-09-27 多情剑客无情剑;

将java标准的数据结构ArrayList和HashMap转换成json对象和数组很简单

只需要JSONArray.fromObject(obj);或者JSONObject.fromObject(obj);

将json对象转换成Map（必须用到遍历）

    public static void main(String[] args){
         HashMap<String, Object> map = new HashMap<String, Object>(); 
         map.put("name", "Tom");
         map.put("age", 12);
         JSONObject obj =JSONObject.fromObject(map);
         System.out.println(obj);// {"name":"Tom","age":12}
         
         HashMap<String, Object> map1= new HashMap<String, Object>();
         Iterator it =obj.keys();
         while(it.hasNext()){
             String key =(String)it.next();
             Object value= obj.get(key);
             map1.put(key, value);         
         }
         System.out.println(map1);//{name=Tom, age=12}
         System.out.println(JSONObject.fromObject(map1)); //{"name":"Tom","age":12}     
    }

public static void main(String[] args){
         ArrayList<String> list = new ArrayList<String>();
         list.add("Tom");
         list.add("Lisa");
         System.out.println(list);//[Tom, Lisa]
         JSONArray array = JSONArray.fromObject(list);
         System.out.println(array);// ["Tom","Lisa"]
         
         ArrayList<String> list1 = new ArrayList<String>();
         Iterator<String> it = list.iterator();
         while(it.hasNext()){
             list1.add(it.next());
         }
         System.out.println(list1);//[Tom, Lisa]
    }