Decode json returns null in Java

Question

I have the following JSONArray:

[
 {
 "Lng":17.908817,
 "name":"S1",
 "id":1,
 "sensor:":[
 "Temperature",
 "Wind"
 ],
 "Lat":47.089492
 },
 {
 "Lng":17.908458,
 "name":"S2",
 "id":2,
 "sensor:":[
 "Temperature",
 "Wind",
 "Humidity"
 ],
 "Lat":47.089246
 },
 {
 "Lng":17.908222,
 "name":"S3",
 "id":3,
 "sensor:":[
 "Wind"
 ],
 "Lat":47.089662
 }
]

I can split it to JSONObject but if I try to split the Object it returns null.

My code:

 Object object = JSONValue.parse(result);
 JSONArray array = (JSONArray)object;
 for(int i = 0 ; i < array.size(); i++){
 System.out.println(array.get(i));
 JSONObject jsonObject = (JSONObject)array.get(i);
 for(int j = 0 ; j < jsonObject.size(); j++){
 System.out.println(jsonObject.get(j));
 }
 }

Result:

{"Lng":17.908817,"name":"S1","sensor:":["Temperature","Wind"],"id":1,"Lat":47.089492}
null
null
null
null
null
{"Lng":17.908458,"name":"S2","sensor:":["Temperature","Wind","Humidity"],"id":2,"Lat":47.089246}
null
null
null
null
null
{"Lng":17.908222,"name":"S3","sensor:":["Wind"],"id":3,"Lat":47.089662}
null
null
null
null
null

Answer 1

A JSONObject (a JSON object) is not indexable. Elements are unordered. What you are trying to do

System.out.println(jsonObject.get(j));

doesn't make sense. Access name-value pairs through their names.

• Sotirios Delimanolis: @user3768431 The array has the name sensor, so you can access it with jsonObject.get("sensor").
• Duncan: I realized after i post the question.
• Duncan: One more and I let it. What is the proper way? I tried this: JSONArray array2 = (JSONArray)jsonObject.get("sensor"); but it isnt working.
• Sotirios Delimanolis: @user Which library are you using? I might have gotten them wrong. Also, what does is not working mean? Does it throw an exception? Does it return null?
• Sotirios Delimanolis: @us Oh, there's a : at the end of sensor.

Answer 2

You can use:

Iterator<?> keys = jsonObject.keys();
while( keys.hasNext() ){
 String key = (String)keys.next();
 // use jsonObject.get(key)
}

instead of that "j".

Answer 3

Try to access the JSONObject properties through their keys:

JSONArray array = JSONValue.parse(result);
for(int i = 0 ; i < array.size(); i++) 
{
 System.out.println(array.get(i));
 JSONObject jsonObject = (JSONObject) array.get(i);
 int id = jsonObject.getInt("id");
 String lng = jsonObject.getString("Lng");
 String lat = jsonObject.getString("Lat");
 Object sensor = jsonObject.getString("sensor");
 String name = jsonObject.getString("name");
 System.out.println(id);
 System.out.println(name);
 System.out.println(sensor);
 System.out.println(lat);
 System.out.println(lon);
}