If anybody looking for converting the XML to Json, the below method can be used. It encloses all JSONObject inside a JSONArray.

public JSONObject getJSONFromXML(String xml) {
    JSONObject jsonObject = null;
    try {
        jsonObject = XML.toJSONObject(xml);
        convertJsonObjectToArray(jsonObject);
    } catch (JSONException e) {
        System.out.println("Error in parsing JSON From xml: " + e);
    }
    return jsonObject;
}

private void convertJsonObjectToArray(JSONObject jsonObject) throws JSONException {
    for (Object key : jsonObject.keySet()) {
        Object val = jsonObject.get(key.toString());
        if (val instanceof JSONObject) {
            convertJsonObjectToArray((JSONObject) val);
            JSONArray jsonArray = new JSONArray();
            jsonArray.put(val);
            jsonObject.put(key.toString(), jsonArray);
        } else if (val instanceof JSONArray) {
            JSONArray jsonArray = (JSONArray) val;
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject obj = (JSONObject) jsonArray.get(i);
                convertJsonObjectToArray(obj);
            }
        }
    }
}

In case it helps anyone, further to meda's reply. Here's how you make this work with XElement rather than xmlTextWriter and XDocument

XNamespace ns = "http://james.newtonking.com/projects/json";
var items = new XElement("items",new XAttribute(XNamespace.Xmlns+"json",ns));

   items.Add(new XElement("item",new XAttribute(ns+"Array",true),
                        new XElement("name", "name"),
                        new XElement("Detail", "detail")));

then to convert it

 XmlDocument doc = new XmlDocument();
            doc.LoadXml(items.ToString());
            var converted JsonConvert.SerializeXmlNode(doc);

Based on Mario's solution, I made some changes, specially for nested children in the Json object. The xmlJSONObj is the same, but the obj param is a List that contains the path to the JSON child, and the index param is only required for the recursion (it should start at 0 in the first execution).

/**
       * Forces a JSON Object to be an Array. When converting from XML to JSON, There may be cases in
       * which we want a list of elements in the final JSON but there is only one element in the XML
       * file, so the XML.toJSONObject method will fail. This methods forces a JSON element to be an
       * array instead of just a JSON Object.
       * 
       * @param xmlJSONObj obtained by passing the XML through the method toJSONObject
       * @param obj list of String that contains the path to the JSON child to convert to Array
       * @param index required for recursion, starts at 0
       * @throws org.json.JSONException
       */
      public static void forceToJSONArray(JSONObject xmlJSONObj, List<String> obj, int index)
          throws org.json.JSONException {
        Object myObj = xmlJSONObj.opt(obj.get(index));
        if (myObj instanceof JSONObject && obj.size() == index + 1) {
          JSONObject myJSONObj = (JSONObject) myObj;
          JSONArray jsonArray = new JSONArray();
          jsonArray.add(myJSONObj);
          xmlJSONObj.put(obj.get(index), jsonArray);
        } else if (myObj instanceof JSONObject) {
          forceToJSONArray((JSONObject) myObj, obj, index + 1);
        }
      }

Example:

We have this JSON:

{
   "person":{
      "name":"Tony",
      "data":{
         "car":"Toyota"
      }
   }
}

And we want this JSON:

{
   "person":{
      "name":"Tony",
      "data":{
         "car":["Toyota"]
      }
   }
}

We should call the method like this:

forceToJSONArray(xmlJSONObj, Arrays.asList("person", "data", "car"), 0);