TIOBE - Java Coding Standard

Rule: Design101

Synopsis:	Classes with only private constructors should be declared as final
Language:	Java
Severity Level:	3
Category:	Design

Description:

Checks that a class which has only private constructors is declared as final. Doesn't check for classes nested in interfaces or annotations, as they are always final there.

public class ClassWithPrivateConstructor { // violation
    private ClassWithPrivateConstructor() {
    }
}