將java標準的數據結構ArrayList和HashMap轉換成json對象和數組很簡單

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

將json對象轉換成Map（必須用到遍歷）

    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]
    }

（精華）將json數組和對象轉換成List和Map(小龍哥和牛徳鶴的對話)