I have two ways of checking if a List is empty or not
if (CollectionUtils.isNotEmpty(listName))
and
if (listName != null
Unless you are already using CollectionUtils I would go for List.isEmpty(), less dependencies.
Performance wise CollectionUtils will be a tad slower. Because it basically follows the same logic but has additional overhead.
So it would be readability vs. performance vs. dependencies. Not much of a big difference though.