title: What is the "system-dependent default" thread pool?
body: <p>From the <a href="http://docs.oracle.com/javase/7/docs/api/java/nio/channels/AsynchronousFileChannel.html"><code>AsynchronousFileChannel</code></a> API:</p>
  
  <blockquote>
    <p>When an AsynchronousFileChannel is created without specifying a thread pool then the channel is associated with a <strong>system-dependent default thread pool</strong> that may be shared with other channels.</p>
  </blockquote>
  
  <p>I haven't seen this terminology anywhere else, and I haven't found any concrete explanation via web search. What exactly is the system-dependent default thread pool? What are its characteristics? And how might they vary between systems?</p>