IThis, IThat, ITheOther

I have seen projects where every class had implemented an interface by default. The interfaces always had the same names as the classes except they were prefixed with an (I). I don't call this good design. The flexibility that an interface gives you has a cost. If an interface is not paying for this cost it should be removed. Only use interfaces when the flexibility is required. It is often difficult to tell in advance where this flexibility is needed so it is usually best to add an interface when the flexibility is required. Also instead of using the (I) prefix I prefer to name the interface by how the client will use the class. So instead of creating and IBook interface for a Book class, I could create a Readable interface instead. Removing the last trace of Hungarian notation from my code.