How to sort array of json objects in java

Question

i have two json objects in jsonarray like this

"errorCode": "1",
"data": [
    {
        "messageId": 590,
        "message": "WvZiT3RPm7feC6Hxsa/Ing==",
        "messageType": "CHAT",
        "sentOn": "01:51 PM, Apr 06, 2013",

        "mainParent": 589,
        "officeId": "19",
        "webParent": 590
    },
    {
        "messageId": 589,
        "message": "1A45rtoC3Cy88h73TEvDqQ==",
        "messageType": "CHAT",
        "sentOn": "01:50 PM, Apr 06, 2013",

        "parent": 0,
        "signImg": null,
        "mainParent": 589,
        "officeId": "19",
        "webParent": 1
    }
]

so i want to sort in ascending order based on message id key. i tried with comparator with object type as json object, i am getting error in compareto method. please suggest me

Answer 1

I am posting the answer here helping others who are facing the issue with this kind of problems.

public static JSONArray getSortedList(JSONArray array) throws JSONException {
            List<JSONObject> list = new ArrayList<JSONObject>();
            for (int i = 0; i < array.length(); i++) {
                    list.add(array.getJSONObject(i));
            }
            Collections.sort(list, new SortBasedOnMessageId());

            JSONArray resultArray = new JSONArray(list);

            return resultArray;
}

This part of the code will help to sort the json array

Check out the SortBasedOnMessageId class below.

public class SortBasedOnMessageId implements Comparator<JSONObject> {
    /*
    * (non-Javadoc)
    * 
    * @see java.util.Comparator#compare(java.lang.Object, java.lang.Object)
    * lhs- 1st message in the form of json object. rhs- 2nd message in the form
    * of json object.
    */
    @Override
    public int compare(JSONObject lhs, JSONObject rhs) {
        try {
            return lhs.getInt("messageId") > rhs.getInt("messageId") ? 1 : (lhs
                .getInt("messageId") < rhs.getInt("messageId") ? -1 : 0);
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return 0;

    }
}

Answer 2

Since Java 8 this can be solved with Integer.compare() function within 1 method:

private JSONArray getSortedMessages(JSONArray array) throws JSONException {
    List<JSONObject> list = new ArrayList<>();
    for (int i = 0; i < array.length(); i++) {
        list.add(array.getJSONObject(i));
    }
    list.sort((a1, a2) -> {
        try {
            return Integer.compare(a1.getInt("messageId"), a2.getInt("messageId"));
        } catch (JSONException e) {
            e.printStackTrace();
        }
        return 0;
    });
    return new JSONArray(list);
}