There are two 'patterns' for creating utils classes:
- use an abstract class
- use a final class with private ctor.

I prefer the former since the end result is the same - you can't instantiate the class - and it's also a lot shorter. Abstract also leaves the door open in the future for the very rare case of wanting to extend the class.
Final class + private ctor() seems way too defensive to me; the user can still mess with the class if she really wants to.

I've noticed the style in ES is final/private ctor so I can change to that, no problem.