title: Can I decorate Joiner class of Guava
body: <p>I have a <code>List&lt;String&gt;</code> and we are using Joiner to get the comma separated presentation of that List but now we need to do little enhancement, We need to capitalize the values in the List. Now the code was - 
  <br></p>
  
  <pre><code>String str = Joiner.on(',').skipNulls().join(myValueList);
  </code></pre>
  
  <p>But now as I need to capitalize the Strings present in values I need to iterate it first to capitalize and then pass to Joiner to join, but I den't think this is a good approach as it'll iterate the List twice, one to capitalize and then Joiner will iterate to Join.<br> 
  Is there any other utility method that I'm missing which may do this in one iteration. <br><br>
  How will you do it with Guava?</p>