JSON Parsing taking too much time - Android

Question

I have a JSON file airports.json which contains 5720 objects, I want to parse the file in Java into Objects Airport. The code below is how I parse it, the problem is, it is taking too much time to completely parse all the file, about 1 min and 50 sec.

    ArrayList<Airport> arrayAirports = new ArrayList<>();
    String json_response = loadJSONFromAsset();
    try {
        JSONObject airports = new JSONObject(json_response.trim());

        Log.d("Length Array 0", String.valueOf(airports.names().length()));
        Log.d("Length Array 1", String.valueOf(arrayAirports.size()));
        for(int i = 0; i<airports.names().length(); i++){
                JSONObject jsonAirport = airports.getJSONObject(airports.names().getString(i));
                Airport newAirport = new Airport();
                newAirport.name = jsonAirport.getString("name");
                newAirport.city = jsonAirport.getString("city");
                newAirport.country = jsonAirport.getString("country");
                newAirport.latitude = jsonAirport.getString("latitude");
                newAirport.longitude = jsonAirport.getString("longitude");
                newAirport.altitude = jsonAirport.getString("altitude");
                newAirport.iata = jsonAirport.getString("iata");
                newAirport.icao = jsonAirport.getString("icao");
                newAirport.timeZone = jsonAirport.getString("timezone");
                newAirport.dst = jsonAirport.getString("dst");
                arrayAirports.add(newAirport);
        }



    } catch (JSONException e1) {
        e1.printStackTrace();
    }

    Log.d("Length Array 2", String.valueOf(arrayAirports.size()));

Is there a way to parse it quicklier. By the way my friend is parsing it with no time at all using Objective C.

Link to JSON file

Answer 1

Use GSON instead and measure the speed with it. While it is possible possible that just reading the file could take a long time, a whole minute seems pretty bad.

Since you mentioned you don't know how to use GSON, here's a tutorial I wrote for a student on how to use GSON . It assume you're getting the file from a network call though, so you need to apply it to use your local JSON file.

Answer 2

Don't know if it matters for performance, but you shouldn't call names() repeatedly. Assign to variable before loop, then use it.

JSONArray names = airports.names();
Log.d("Length Array 0", String.valueOf(names.length()));
Log.d("Length Array 1", String.valueOf(arrayAirports.size()));
for(int i = 0; i<names.length(); i++){
    JSONObject jsonAirport = airports.getJSONObject(names.getString(i));
    // code
}

Better yet, use length() and keys() :

Log.d("Length Array 0", String.valueOf(airports.length()));
Log.d("Length Array 1", String.valueOf(arrayAirports.size()));
for (Iterator<String> nameIter = airports.keys(); nameIter.hasNext(); ){
    String name = nameIter.next();
    JSONObject jsonAirport = airports.getJSONObject(name);
    // code
}

Answer 3

You are putting a (I guess?) large JSON data file into a JSONObject directly.

In this case it would be recommended to use a token based reader, such as JsonReader .

Pasted directly from the docs:

public List readJsonStream(InputStream in ) throws IOException {
    JsonReader reader = new JsonReader(new InputStreamReader( in , "UTF-8"));
    try {
        return readMessagesArray(reader);
        finally {
            reader.close();
        }
    }

    public List readMessagesArray(JsonReader reader) throws IOException {
        List messages = new ArrayList();

        reader.beginArray();
        while (reader.hasNext()) {
            messages.add(readMessage(reader));
        }
        reader.endArray();
        return messages;
    }

    public Message readMessage(JsonReader reader) throws IOException {
        long id = -1;
        String text = null;
        User user = null;
        List geo = null;

        reader.beginObject();
        while (reader.hasNext()) {
            String name = reader.nextName();
            if (name.equals("id")) {
                id = reader.nextLong();
            } else if (name.equals("text")) {
                text = reader.nextString();
            } else if (name.equals("geo") && reader.peek() != JsonToken.NULL) {
                geo = readDoublesArray(reader);
            } else if (name.equals("user")) {
                user = readUser(reader);
            } else {
                reader.skipValue();
            }
        }
        reader.endObject();
        return new Message(id, text, user, geo);
    }

    public List readDoublesArray(JsonReader reader) throws IOException {
        List doubles = new ArrayList();

        reader.beginArray();
        while (reader.hasNext()) {
            doubles.add(reader.nextDouble());
        }
        reader.endArray();
        return doubles;
    }

    public User readUser(JsonReader reader) throws IOException {
        String username = null;
        int followersCount = -1;

        reader.beginObject();
        while (reader.hasNext()) {
            String name = reader.nextName();
            if (name.equals("name")) {
                username = reader.nextString();
            } else if (name.equals("followers_count")) {
                followersCount = reader.nextInt();
            } else {
                reader.skipValue();
            }
        }
        reader.endObject();
        return new User(username, followersCount);
    }
}