Hi,
thank you for your post.
There was a bug in jfuzzylite 5.0 which caused this issue. This has been resolved in jfuzzylite 5.0.1. Please download from
http://fuzzylite.com/download/jfuzzylite5/
or
https://github.com/fuzzylite/jfuzzylite/releases/download/5.0.1/jfuzzylite-5.0.1.jar
Where did you originally downloaded the library from? Are you using Maven? If so, updating the version to 5.0.1 should work too. Please, let me know.
Cheers.