title: ConcurrentHashMap parallelismThreshold
body: <p>The <code>ConcurrentHashMap</code> got a couple new methods.
  I have two questions regarding them:  </p>
  
  <ol>
  <li>Why aren't they declared in <code>ConcurrentMap</code>?</li>
  <li>What exactly does the <code>parallelismThreshold</code> mean or do?</li>
  </ol>