How to convert list map to json string and json to list map

Question

I want to convert list map to json (First Activity) then json to list map (Third Activity) I am using built-in json library Don't Use Any Third party library

Code to convert ListMap to json

        {
            
            
        }
        else
        {
            HashMap<Object, Object> map = new HashMap<>();
            
            map.put("title",list_string_title);
            map.put("id",list_string_id);
            JSONObject jsonObject = new JSONObject(map);
            
            FileUtils.writeFile(getPathData(scr_id),jsonObject.toString());
        }

When the program find the json file I want it to add it into a listMap

Answer 1

Need to pass a TypeReference to readValue with your output type

ObjectMapper mapper = new ObjectMapper();
List<Map<String, Object>> data = mapper.readValue(json, new TypeReference<List<Map<String, Object>>>(){});

Answer 2

You can iterate over the JSONObject and add it to the map, in your case your value is a list, it will be treated as JSONArray, you can try the following code

public Map<Object, Object> jsonToMap(JSONObject jsonObject) throws JSONException {

        Iterator<String> itr = jsonObject.keys();   
        Map<Object, Object> mapFromJSON = new HashMap<Object,Object>();
        
        while(itr.hasNext()) {
            Object key = itr.next();
            JSONArray jsonArray = (JSONArray) jsonObject.get((String) key);
            ArrayList list = new ArrayList<Object>();
            
            for(int i=0; i< jsonArray.length(); i++) {
                list.add(jsonArray.get(i));
            }
            mapFromJSON.put(key, list); 
        }
        return mapFromJSON;
    }

if your list contains JSONObject, you can use recursion.