title: How do I make one Java thread return before some of its child threads finish?
body: <p>I have 2 nested threads.</p>
  
  <p>First thread starts multiple instances of second thread. Each second thread has to sleep for some time (5 seconds).</p>
  
  <p>I want to start the first thread and return a message to user immediately, but it seems my first thread waits until all the children of second thread to finish.</p>
  
  <p>How can I achieve this? Any help?</p>