title: ConcurrentHashMap constructor parameters?
body: <p>I am wondering about the parameters for constructing a <code>ConcurrentHashMap</code>:</p>
  
  <ul>
  <li><code>initialCapacity</code> is 16 by default (understood).</li>
  <li><code>loadFactor</code> is 0.75 by default.</li>
  <li><code>concurrencyLevel</code> is 16 by default.</li>
  </ul>
  
  <p>My questions are:</p>
  
  <ul>
  <li>What criteria should be used to adjust <code>loadFactor</code> up or down?</li>
  <li>How do we establish the number of concurrently updating threads?</li>
  <li>What criteria should be used to adjust <code>concurrencyLevel</code> up or down?</li>
  </ul>
  
  <p>Additionally:</p>
  
  <ul>
  <li>What are the hallmarks of a <strong>good</strong> hashcode implementation? (If an SO question addresses this, just link to it.)</li>
  </ul>
  
  <p>Thank you!</p>