nullPointerException when using Aysnctask, android

Question

I am writing an android application to get the current weather using latitude , longitude using openWeatherMap API. I used Aysnctask to get the weather, but the application crashes and it gives me a nullPointerException.

here the aysnctask:

private class JSONWeatherTask extends AsyncTask<String, Void, Weather> {

        @Override
        protected Weather doInBackground(String... params) {

            Weather weather = new Weather();
        //  String data = ( (new WeatherHttpClient()).getWeatherData(params[0]));

            String data = ( (new WeatherHttpClient()).getWeatherData(params[0],params[1]));
            try {
                weather = JSONWeatherParser.getWeather(data);

                // Let's retrieve the icon
                weather.iconData = ( (new WeatherHttpClient()).getImage(weather.currentCondition.getIcon()));

            } catch (JSONException e) {             
                e.printStackTrace();
            }
            return weather;

    }





    @Override
        protected void onPostExecute(Weather weather) {         
            super.onPostExecute(weather);

            if (weather.iconData != null && weather.iconData.length > 0) {
                Bitmap img = BitmapFactory.decodeByteArray(weather.iconData, 0, weather.iconData.length); 
                imgView.setImageBitmap(img);
            }


            condDescr.setText(weather.currentCondition.getCondition() + "(" + weather.currentCondition.getDescr() + ")");
            temp.setText("" + Math.round((weather.temperature.getTemp() - 275.15)) + "°C");
            hum.setText("" + weather.currentCondition.getHumidity() + "%");
            press.setText("" + weather.currentCondition.getPressure() + " hPa");
            windSpeed.setText("" + weather.wind.getSpeed() + " mps");
            windDeg.setText("" + weather.wind.getDeg() + "°");

        }

 }

the parameters of doInBackground method should be current latitude, longitude. I call the aysnktask like this:

JSONWeatherTask task = new JSONWeatherTask();
    task.execute(new String[]{currentLatitude,currentLongitude});

and I make the connection to openWeatherMap like this:

public String getWeatherData(String lat,String lng) {
        HttpURLConnection con = null ;
        InputStream is = null;

        try {
            con=(HttpURLConnection)(new URL("http://api.openweathermap.org/data/2.5/weather?lat=%"+Double.parseDouble(lat)+"&lon="+Double.parseDouble(lng))).openConnection();   

            con.setRequestMethod("GET");
            con.setDoInput(true);
            con.setDoOutput(true);
            con.connect();

            // Let's read the response
            StringBuffer buffer = new StringBuffer();
            is = con.getInputStream();
            BufferedReader br = new BufferedReader(new InputStreamReader(is));
            String line = null;
            while (  (line = br.readLine()) != null )
                buffer.append(line + "\r\n");

            is.close();
            con.disconnect();
            return buffer.toString();
        }
        catch(Throwable t) {
            t.printStackTrace();
        }
        finally {
            try { is.close(); } catch(Throwable t) {}
            try { con.disconnect(); } catch(Throwable t) {}
        }

        return null;

    }

the nullPointerException is at this line :

weather = JSONWeatherParser.getWeather(data);

here is the logCat:

12-03 11:34:29.110: E/AndroidRuntime(16271): FATAL EXCEPTION: AsyncTask #1
12-03 11:34:29.110: E/AndroidRuntime(16271): java.lang.RuntimeException: An error occured while executing doInBackground()
12-03 11:34:29.110: E/AndroidRuntime(16271):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.lang.Thread.run(Thread.java:856)
12-03 11:34:29.110: E/AndroidRuntime(16271): Caused by: java.lang.NullPointerException
12-03 11:34:29.110: E/AndroidRuntime(16271):    at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at org.json.JSONTokener.nextValue(JSONTokener.java:94)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at org.json.JSONObject.<init>(JSONObject.java:154)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at org.json.JSONObject.<init>(JSONObject.java:171)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at com.survivingwithandroid.weatherapp.JSONWeatherParser.getWeather(JSONWeatherParser.java:42)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at com.survivingwithandroid.weatherapp.MainActivity$JSONWeatherTask.doInBackground(MainActivity.java:290)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at com.survivingwithandroid.weatherapp.MainActivity$JSONWeatherTask.doInBackground(MainActivity.java:1)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-03 11:34:29.110: E/AndroidRuntime(16271):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)

this is getWeather method :

public static Weather getWeather(String data) throws JSONException  {
        Weather weather = new Weather();

        // We create out JSONObject from the data
        JSONObject jObj = new JSONObject(data);

        // We start extracting the info
        Location1 loc = new Location1();

        JSONObject coordObj = getObject("coord", jObj);
        loc.setLatitude(getFloat("lat", coordObj));
        loc.setLongitude(getFloat("lon", coordObj));

        JSONObject sysObj = getObject("sys", jObj);
        loc.setCountry(getString("country", sysObj));
        loc.setSunrise(getInt("sunrise", sysObj));
        loc.setSunset(getInt("sunset", sysObj));
        loc.setCity(getString("name", jObj));
        weather.location = loc;

        // We get weather info (This is an array)
        JSONArray jArr = jObj.getJSONArray("weather");

        // We use only the first value
        JSONObject JSONWeather = jArr.getJSONObject(0);
        weather.currentCondition.setWeatherId(getInt("id", JSONWeather));
        weather.currentCondition.setDescr(getString("description", JSONWeather));
        weather.currentCondition.setCondition(getString("main", JSONWeather));
        weather.currentCondition.setIcon(getString("icon", JSONWeather));

        JSONObject mainObj = getObject("main", jObj);
        weather.currentCondition.setHumidity(getInt("humidity", mainObj));
        weather.currentCondition.setPressure(getInt("pressure", mainObj));
        weather.temperature.setMaxTemp(getFloat("temp_max", mainObj));
        weather.temperature.setMinTemp(getFloat("temp_min", mainObj));
        weather.temperature.setTemp(getFloat("temp", mainObj));

        // Wind
        JSONObject wObj = getObject("wind", jObj);
        weather.wind.setSpeed(getFloat("speed", wObj));
        weather.wind.setDeg(getFloat("deg", wObj));

        // Clouds
        JSONObject cObj = getObject("clouds", jObj);
        weather.clouds.setPerc(getInt("all", cObj));

        // We download the icon to show


        return weather;
    }