title: How does EL empty operator work in JSF?
body: <p>In JSF an component can be rendered or not using the EL empty operator </p>
  
  <pre><code>rendered="#{not empty myBean.myList}"
  </code></pre>
  
  <p>As I've understood the operator works both as null-check, but also check checks if the list is empty. </p>
  
  <p>I want to do empty checks on some objects of my own custom class, which interface(s) or parts of interfaces do I need to implement?
  Which interface is the empty operator compatible with?</p>