22

I have a very large response from server of JSON string. I converted it to JSON object and then get the keys and iterate it.

The problem is that when I iterate it isnt in the same order as in response from server.

Next then I apply another method by adding all the keys in List<String> and the sort it and then get the iterator of that but still it isn't as I required (as in response).

Code example is here:

JSONObject jsonObject = new JSONObject(responseString);
    Iterator<String> myIter = jsonObject.keys();


    List<String> sortKey = new ArrayList<String>();

    while(myIter.hasNext()){
        sortKey.add(myIter.next());
    }
    Collections.sort(sortKey);
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3 Answers 3

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18

The order of the keys of a JSON object is not supposed to be meaningful. If you want a specific order, you should use an array, not an object.

Your Java code sorts the keys alphabetically. There is no way to get the initial ordering of the keys in the object.

Reference 1:

The order of the keys is undefined

Reference 2:

An object is an unordered set of name/value pairs

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3 Comments

Thanks man but please see the next one question now. stackoverflow.com/questions/7053915/…
To be honest I don't think this answer is 100% true. For example, for a currency exchange array, it can be {name -> info} pairs and name can be sorted by how "important" it is, i.e. USD is the 1st etc. Of course you can put these paris into array entries, but then there's just an additional nest. My point is there can be a lot of good reasons for the order of items in a "dictionary" object to be meaningful. If it's not part of the json spec, then the spec is wrong, not the people want to keep their data structure as clean and simple as possible.
@superarts.org: the question is not whether the keys of a JavaScript object should be ordered. The question is wheteher the keys of a JavaScript object are ordered. And they're not.
17

You can use Sorted map to put keys and values into. Something like this

 public static List listFromJsonSorted(JSONObject json) {
    if (json == null) return null;
    SortedMap map = new TreeMap();
    Iterator i = json.keys();
    while (i.hasNext()) {
        try {
            String key = i.next().toString();
            JSONObject j = json.getJSONObject(key);
            map.put(key, j);
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }

    return new LinkedList(map.values());
}
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Comments

0

I came across this similar problem while working on section in my android app which displays a list of 1024+ websites alphabetically. Since the json traversal was not in sorted order , I just inserted the json values during traversal into a table ( I m using list adapters in my app) and obtained sorted list of websites with cursor.

So if you are saving what you are fetching from server, you can just query your database to sort the values in the order your want.

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1 Comment

yes first thing comes in mind that you told but it will definitely take time but I am looking for to sort through json and java functions

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