title: Hashmap stuck on get
body: <p>I have a strange issue with HashMap.<br>
  There are multiple threads that accessing same hashmap (not threadsafe).</p>
  
  <p>Sometime, the process gets stuck. </p>
  
  <p>when I inspect the thread stack, i see many threads in state:</p>
  
  <pre><code>java.lang.Thread.State: RUNNABLE
      at java.util.HashMap.get(HashMap.java:303) 
  </code></pre>
  
  <p>Note this happens very rare. And can't be reproduced on demand.</p>
  
  <p>Why it gets stuck?</p>
  
  <p>There is no synchronization on hashmap.</p>
  
  <p>keys are strings</p>