title: How does the method scheduledExecutorService.scheduleAtFixedRate() ensures real-time execution?
body: <p>Because I'm executing a time critical task every second, I compared several methods to find the best way to ensure that my task is really executed in fixed time steps. After calculating the standard derivation of the error for all methods it seems like using the method <code>scheduledExecutorService.scheduleAtFixedRate()</code> leads to the best results, but I don't have a clue why it is so.</p>
  
  <p>Does anybody know how that method internally works? How does it for example in comparison to a simple <code>sleep()</code> ensure that the referenced task is really executed in fixed time steps?</p>