How to loop through json array of json object in java

Question

I am trying to loop through the json file and find the value of particular json object. Here is my sample json:

{
  "diagram":[
             {"size":{"width":30,"height":20},"color":"blue","id":1}, 
             {"color":"red","id":2},
             {"size:{"height":30}", "id":3}
            ]
}

What i want to do is to iterate through the file and find the "id" element.

I used below code to convert the JsonFile into JsonObject and to get the value of "diagram" object

JSONArray jsonArray = new JSONArray();
JSONParser parser = new JSONParser();
Object obj = parser.parse(new FileReader("D:/test.json"));
JSONObject jsonObj = (JSONObject) obj;
for(Iterator iterator = jsonObj.keySet().iterator(); iterator.hasNext();) {
      String diagramKey = (String) iterator.next();
      jsonArray.put(jsonObj.get(diagramKey));
}

With the above code i was able to get the value of diagram object and i have put that into the jsonArray

When i am trying to print the array object i am getting output as

[[
  {"size":{"width":30,"height":20},"color":"blue","id":1}, 
  {"color":"red","id":2},
  {"size:{"height":30}", "id":3}
]]

and the jsonArray length is coming as 1.

How to loop through the above jsonArray and find the id of each individual element

In your input the diagram is an array which contains multiple objects. In your output you have an array of those arrays. It looks like you're handling a single diagram so far, so your output array contains a single array. You could loop over that inner array and you'd find the three ids of the objects it contains — Aaron, May 16 '19 at 09:40

score 1 · Answer 1 · answered May 16 '19 at 09:54

Verify your JSON too and check below code. 

public class MyTest {

    public static void main(String[] args) throws JSONException {
        String str = "{\r\n" + 
                "   \"diagram\": [{\r\n" + 
                "           \"size\": {\r\n" + 
                "               \"width\": 30,\r\n" + 
                "               \"height\": 20\r\n" + 
                "           },\r\n" + 
                "           \"color\": \"blue\",\r\n" + 
                "           \"id\": 1\r\n" + 
                "       },\r\n" + 
                "       {\r\n" + 
                "           \"color\": \"red\",\r\n" + 
                "           \"id\": 2\r\n" + 
                "       },\r\n" + 
                "       {\r\n" + 
                "           \"size\": {\r\n" + 
                "               \"height\": 30\r\n" + 
                "           },\r\n" + 
                "           \"id\": 3\r\n" + 
                "       }\r\n" + 
                "   ]\r\n" + 
                "}";

        JSONObject jo = new JSONObject(str);
        final JSONArray geodata = jo.getJSONArray("diagram");
        int arrLength = geodata.length();
        for(int i = 0; i< arrLength;i++) {
            jo  = geodata.getJSONObject(i);
            System.out.println(jo.get("id"));
        }
    }
}

score 0 · Answer 2 · answered May 16 '19 at 09:57

Your json format is wrong. You can always validate your json format using tools online

Correct json format

{  
   "diagram":[  
      {  
         "size":{  
            "width":30,
            "height":20
         },
         "color":"blue",
         "id":1
      },
      {  
         "color":"red",
         "id":2
      },
      {  
         "size":{  
            "height":30
         },
         "id":3
      }
   ]
}

How to loop through json array of json object in java

2 Answers2