Android: crash on launching a class : my app crashes when I try to launch it:

    DownloadTask downloadTask = new DownloadTask();

here there is the code of the class:

>    private class DownloadTask extends AsyncTask<String, Void, String>{
>
>        @Override
>        protected String doInBackground(String... url) {
>
>            // For storing data from web service
>            String data = "";
>
>            try{
>                // Fetching the data from web service
>                data = downloadUrl(url[0]);
>            }catch(Exception e){
>                Log.d("Background Task",e.toString());
>            }
>            return data;
>        }
>
>        @Override
>        protected void onPostExecute(String result) {
>            super.onPostExecute(result);
>            ParserTask parserTask = new ParserTask();
>            // Invokes the thread for parsing the JSON data
>            parserTask.execute(result);
>        }
>    }


Where am I going wrong?
