Clean Code chapter 14 This chapter is a case study in successive refinement. You will see a module that started well but did not scale. Then you will see how the module was refactored and cleaned. Most of us have had to parse command-line arguments from time to time. If we don’t have a convenient utility, then we simply walk the array of strings that is passed into the main but none of them do exactly what I want. So, of course, I decided to write my own. I call it: Args.

 Args is very simple to use. You simply construct the Args class with the input argu-

ments and a format string, and then query the Args instance for the values of the argu- ments. You can see how simple this is. We just create an instance of the Args class with two parameters. The first parameter is the format, or schema, string: "l,p#,d*." It defines three command-line arguments. The first, –l, is a boolean argument. The second, -p, is an integer argument. The third, -d, is a string argument. The second parameter to the Args constructor is simply the array of command-line argument passed into main.

 If  the  constructor  returns  without  throwing  an  ArgsException,  then  the  incoming

command-line was parsed, and the Args instance is ready to be queried. Methods like getBoolean, getInteger, and getString allow us to access the values of the arguments by their names.

 If there is a problem, either in the format string or in the command-line arguments

themselves, an ArgsException will be thrown. A convenient description of what went wrong can be retrieved from the errorMessage method of the exception.

Args Implementation

Listing 14-2 is the implementation of the Args class. Please read it very carefully. I worked hard on the style and structure and hope it is worth emulating.