title: Why does Java HashMap contain null values in the debug view
body: <p>While debugging I found a strange behavior.</p>
  
  <p>I got a <code>HashMap&lt;Integer, Set&lt;Term&gt;&gt;</code> (Term is a class which only contains a String) the normal <code>toString()</code> shows this: </p>
  
  <p><img src="https://i.stack.imgur.com/W3xC9.png" alt="enter image description here"></p>
  
  <p>When I click the table property of the HashMap I get this:</p>
  
  <p><img src="https://i.imgur.com/dP8eVCE.png" alt="enter image description here"></p>
  
  <p>My Question now, why are there null values in the table <code>toString()</code> ?</p>
  
  <p>Edit: Thanks for your fast answers! If I could, I would accept all of them... </p>