Question

I had been looking at some code developed by an off-shore group. I see at least one “constant interface” per module defined.
Example (not real world) :

public interface RequestConstants{
  //a mix of different constants(int,string,...)
  public static final int MAX_REQUESTS = 9999;
  public static final String SAMPLE_REQUEST = "Sample Request";
}

Per my understanding it is an anti-pattern as these does not any utility in run-time, and should be avoided or tackled in a different way.
What are elegant ways to represent this? Can enums be used instead?

Answer 1

En enum is probably not a good idea unless all the parameters are closely related. With the two parameters in your example I’d say they are not closely enough related to qualify as an enum.

But it’s not necessarily a Bad Idea to include a constants class / interface like this. It does have the advantage of being centralized, which means this configuration stuff can easily be moved outside of the program — for instance to a properties file, a command-line decoder, a database or even a socket interface — with minimal impact to the other classes. It’s really a question of what direction the design will take.

Unless you are thinking of going down that path, however, I’d say static finals in the classes where the respective parameters are used is the way to go, as has been suggested already.