title: Is there a purpose to having a constant for null?
body: <p>I recently saw something in some code that made me curious if it was actually having some kind of optimization or performance impact.  It was a line like this in a constants file:</p>
  
  <pre><code>public static final Object NULL = null;
  </code></pre>
  
  <p>Then, throughout the code, rather than explicitly using the <code>null</code> keyword, it would be referred to with <code>Constants.NULL</code>.</p>
  
  <p>I've seen this kind of thing before with something like:</p>
  
  <pre><code>public static final String EMPTY_STRING = "";
  </code></pre>
  
  <p>... and that seemed to make at least a little bit of sense, if it's an attempt to avoid creating lots of duplicate <code>""</code> instances.  But does it really make any difference with <code>null</code>, since it's not actually any kind of object?  Is there something I'm missing?</p>