title: what does the three dots in "doInBackground(URL... urls)" mean?
body: <p>what does the "..." in each function mean? and why in the last function, there is no "..."?</p>
  
  <pre><code>private class DownloadFilesTask extends AsyncTask&lt;URL, Integer, Long&gt; {
       protected Long doInBackground(URL... urls) {
           int count = urls.length;
           long totalSize = 0;
           for (int i = 0; i &lt; count; i++) {
               totalSize += Downloader.downloadFile(urls[i]);
               publishProgress((int) ((i / (float) count) * 100));
               // Escape early if cancel() is called
               if (isCancelled()) break;
           }
           return totalSize;
       }
  
       protected void onProgressUpdate(Integer... progress) {
           setProgressPercent(progress[0]);
       }
  
       protected void onPostExecute(Long result) {
           showDialog("Downloaded " + result + " bytes");
       }
   }
  </code></pre>