How does EL empty operator work in JSF?

In JSF an component can be rendered or not using the EL empty operator

rendered="#{not empty myBean.myList}"

As I've understood the operator works both as null-check, but also check checks if the list is empty.

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?