title: Hashmap get returns null
body: <p>I have two Hashmaps</p>
  
  <pre><code>HashMap&lt;Integer, Integer&gt; inventoryRequirements = new HashMap&lt;Integer, Integer&gt;();
  HashMap&lt;Integer, Integer&gt; inventory = new HashMap&lt;Integer, Integer&gt;();
  </code></pre>
  
  <p>I have a loop that checks current and adds to it:</p>
  
  <pre><code>for(Item item : items){
      int currentRequirement = 0;
      currentRequirement = inventoryRequirements.get(item.get_id());
      inventoryRequirements.put(item.get_id(), currentRequirement++);         
  }
  </code></pre>
  
  <p>I have another loop that checks inventory and adds to it:</p>
  
  <pre><code>for(Item item : items){
      int currentInventory = 0;
      // this next line returns null
      currentInventory = inventory.get(item.get_id());
      inventory.put(item.get_id(), currentInventory++);           
  }
  </code></pre>
  
  <p>The first one works fine, but the second one pukes and returns a null.  I don't understand why the second one does not work.  Both are initially in the same state as depicted in the code sample.</p>
  
  <p><strong>EDIT</strong></p>
  
  <p>The two HM get populated as you see here - really! I know it may be hard to believe but the first one works and the second one does not.</p>