title: @Size(min, max) but not required
body: <p>Hi In my spring webapp I have a password variable which I want to be at least 0 characters or more than 6 and less than 20. I know that there is annotation:</p>
  
  <pre><code> @Size(min=6, max=20)
  </code></pre>
  
  <p>but I have no idea how to add possibility that password can be 0 characters. Will somebody help me with this?</p>