title: meaning of 'core pool size' in ScheduledThreadPoolExecutor's constructor
body: <p>I'm new to <code>ScheduledThreadPoolExecutor</code> (as I usually use the simple <code>Timer</code>, but people have been advising against it), and I don't quite understand what would be the appropriate integer value to pass to the <code>ScheduledThreadPoolExecutor(int)</code> constructor.</p>
  
  <p>Could anyone explain this? </p>
  
  <p>Thank you</p>