title: crash on launching a class
body: <p>My app crashes when I try to launch it:</p>
  
  <pre><code>DownloadTask downloadTask = new DownloadTask();
  </code></pre>
  
  <p>Here, Is the code of the class:</p>
  
  <pre><code> private class DownloadTask extends AsyncTask&lt;String, Void, String&gt;{
  
      @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);
      }
   }
  </code></pre>
  
  <p>Where am I going wrong?</p>