title: Iterate through nested hashmap
body: <p>How would I go about iterating through a nested HashMap?</p>
  
  <p>The <code>HashMap</code> is setup like this:</p>
  
  <pre><code>HashMap&lt;String, HashMap&lt;String, Student&gt;&gt;
  </code></pre>
  
  <p>Where <code>Student</code> is an object containing a  variable <code>name</code>. If for instance my HashMap looked like this (the following is not my code, it's just to simulate what the contents of the hashmap could be)</p>
  
  <pre><code> hm =&gt; HashMap&lt;'S', Hashmap&lt;'Sam', SamStudent&gt;&gt;
         HashMap&lt;'S', Hashmap&lt;'Seb', SebStudent&gt;&gt;
         HashMap&lt;'T', Hashmap&lt;'Thomas', ThomasStudent&gt;&gt;
  </code></pre>
  
  <p>How could I iterate through all of the single letter keys, then each full name key, then pull out the name of the student?</p>