title: Wait for multiple AsyncTask to complete
body: <p>I am parallelizing my operation by splitting it in the exact number of cores available and then, by start the same number of AsyncTask, performing the same operation but on different portions of data.</p>
  
  <p>I am using <code>executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR, ...)</code> in order to parallelize the execution of them.</p>
  
  <p>I would like to know when every thread finishes its job so that combine all results and perform further operations.</p>
  
  <p>How can I do?</p>