The Robert C. Martin Clean Code Collection (Collection) (Robert C. Martin Series)

by Robert C. Martin

Notice how the program has been split into three main responsibilities. The main program is contained in the PrimePrinter class all by itself. Its responsibility is to handle the execution environment. It will change if the method of invocation changes. For example, if this program were converted to a SOAP service, this is the class that would be affected. The RowColumnPagePrinter knows all about how to format a list of numbers into pages with a certain number of rows and columns. If the formatting of the output needed changing, then this is the class that would be affected. The PrimeGenerator class knows how to generate a list prime numbers. Notice that it is not meant to be instantiated as an object. The class is just a useful scope in which its variables can be declared and kept hidden. This class will change if the algorithm for computing prime numbers changes.