Is StringUtils.EMPTY recommended?

Of course not. Do you really think "" is not clear enough ?

Constants have essentially 3 use cases:

1. Document the meaning of a value (with constant name + javadoc)
2. Synchronize clients on a common value.
3. Provide a shortcut to a special value to avoid some init costs

None apply here.

I use StringUtils.EMPTY, for hiding the literal and also to express that return StringUtils.EMPTY was fully expected and there should return an empty string, "" can lead to the assumption that "" can be easily changed into something else and that this was maybe only a mistake. I think the EMPTY is more expressive.