title: String.format() vs "+" operator
body: <p>What should be used for a basic string concatenation operation ?</p>
  
  <pre><code>String randomString = "hello " + userName + " how are you" ?
  </code></pre>
  
  <p>or</p>
  
  <pre><code>String randomString = String.format("hello %s how are you ?",userName);
  </code></pre>
  
  <p>I feel <code>String.format()</code> gives a better idea of output string.
  But what are actually <strong>pro and cons</strong> in using any of one ?</p>
  
  <p>Is there anything in terms of performance or orphan entries in string literal pool.</p>
  
  <p><strong>Edit</strong> : I am talking about multiple parameters in string, not just one. Around 5 +.</p>
  
  <p><strong>Bonus Question</strong> : Please also share your view on 
  which one should actually use ? any one of these or 3rd one... !! ?</p>