title: Check the existence of a HashMap key
body: <p>In Java, having a HashMap fully filled in with data of such form:</p>
  
  <pre><code>HashMap&lt;Integer, int[]&gt; map = new HashMap&lt;Integer, int[]&gt;(1000000, 1);
  </code></pre>
  
  <p>what is faster when checking the existence of a random key, say 100:</p>
  
  <pre><code>if (map.get(100) == null))
  </code></pre>
  
  <p>or</p>
  
  <pre><code>if (!map.containsKey(100))
  </code></pre>
  
  <p>?</p>
  
  <p>Question is interesting from the micro-optimization point of view.</p>