Classes with only static members or functions

• https://softwareengineering.stackexchange.com/a/369192

You'll often see final "Helper" or other utility classes which have a private constructor and static members. The private constructor contains no logic and serves only to prevent someone from instantiating the class. The final modifier only brings this idea home that this isn't a class you'd ever want to derive from. It is merely a utility class. If done properly, there should be no singleton or other class members which are not themselves static and final.