Sorting JSON array by ID

Question

I wrote code that takes a string that holds a JSON data. I'm sorting my JSON object array by ID. When I'm using my method I get this exception: "org.json.JSONException: A JSONArray text must start with '[' at 1 [character 2 line 1]".

What am I missing here and how to solve it?

private static void ResortJsonByUseCaseID( String jsonArrStr )
{
    JSONArray jsonArr = new JSONArray(jsonArrStr);
    JSONArray sortedJsonArray = new JSONArray();

    List<JSONObject> jsonValues = new ArrayList<JSONObject>();
    for (int i = 0; i < jsonArr.length(); i++) {
        jsonValues.add(jsonArr.getJSONObject(i));
    }

    java.util.Collections.sort( jsonValues, new java.util.Comparator<JSONObject>() {
        private static final String KEY_NAME = "useCaseId";

        @Override
        public int compare(JSONObject a, JSONObject b) {
            String valA = new String();
            String valB = new String();

            try {
                valA = (String) a.get(KEY_NAME);
                valB = (String) b.get(KEY_NAME);
            }
            catch (JSONException e) {
                //do something

                int tal = 9;
            }

            return valA.compareTo(valB);

        }
    });

    for (int i = 0; i < jsonArr.length(); i++) {
        sortedJsonArray.put(jsonValues.get(i));
    }

    jsonArrStr = sortedJsonArray.toString();

}

Answer 1

The code you are describing will only work on a json that looks something like this:

[
  { "useCaseId" : "4", ... },
  { "useCaseId" : "1", ... },
  { "useCaseId" : "a", ... },  
  ...
]

As you can see, the string begins with a [ character, like the exception demanded.

Since "most" jsons begin with { I'm guessing that your json structure is different, and then you'll be required to adjust your code accordingly. For example, if your json array is embedded in an object like "most" jsons are:

{
  "useCases" : [
                 { "useCaseId" : "4", ... },
                 { "useCaseId" : "1", ... },
                 { "useCaseId" : "a", ... },  
                 ...
               ]
}

then you would have to create a JSONObject obj = new JSONObject(jsonArrStr) and then get the JSONArray by calling (JSONArray)obj.get("useCases").