title: ConcurrentHashMap vs Synchronized HashMap
body: <p>What is the difference between using the wrapper class, <code>SynchronizedMap</code>, on a <code>HashMap</code> and <code>ConcurrentHashMap</code>?  </p>
  
  <p>Is it just being able to modify the <code>HashMap</code> while iterating it (<code>ConcurrentHashMap</code>)?</p>