title: about HashMap.get(key) function
body: <p>If I pull out an object out of my HashMap, and then modify it. Will it modify inside the HashMap also? Or, do I need to set it back again to the HashMap after modifying it?</p>
  
  <p>For example:</p>
  
  <pre><code>HashMap&lt;Integer,TwoPoints&gt; loc = new HashMap&lt;Integer,TwoPoints&gt;();
  ...
  ...
  TwoPoints tp = loc.get(Id); //pulls out the object
  tp.setPoint(group, new Point(x,y); //a method to set something inside the object I pulled.
  </code></pre>