““The five letters of the SOLID acronym stand for: Single Responsibility Principle: a class should have one and only one responsibility; that is, only one reason to change. The Lack of Cohesion Of Methods metric indicates the antipattern of too large a class. Open/Closed Principle: a class should be open for extension, but closed against modification. The Case Statement design smell suggests a violation. Liskov Substitution Principle: a method designed to work on an object of type T should also work on an object of any subtype of T. That is, all of T’s subtypes should preserve T’s “contract.” The refused bequest design smell often indicates a violation. Dependency Injection Principle: if two classes depend on each other but their implementations may change, it would be better for them to both depend on a separate abstract interface which is “injected” between them. Demeter Principle: a method can call other methods in its own class, and methods on the classes of its own instance variables; everything else is taboo. A design smell that indicates a violation is inappropriate intimacy.””
