Safe and easy elimination of dead code

One of my projects is an extension to an open source Java project. A new version of the open source project has been released so I sat down to upgrade my baseline code to this new version.
This transition created some compilation problems, which were quite easy to fix (quite easy ~ 2 hours). Naturally, I used this opportunity to do some refactoring.

In particular, I introduced a global factory, and changed the code such that instantiations of major classes are now delegated to a factory method in this factory object, instead of having an explicit, hard-wired, new T() expressions.

Having completed that I noticed I still have a compilation error in one of my classes. It was a small factory class, which I had used for similar purposes as the global one, but to a smaller extent.

Anyway, I thought that this class is not needed anymore since its functionality is already provided by the global factory. If this is indeed that case, then I don't need to bother about fixing this class, I just need to delete it.

The problem: How can I determine whether my program uses a certain class?
The solution: Just delete it. If no new compiler errors appear, then this class is a dead class, and can stay in the trash forever. If not, you can always restore it from the CVS.

So I deleted the class. A new compiler error appeared at another class, but (again) this class seemed to be redundant in the new design. So I deleted this other class, and that's it: All my compiler errors disappeared, indicating that these classes are really, absolutely, definitely dead ("These classes wouldn't "voom" if you put four million volts through it!").

The moral: The easiest way to know if you can delete a class is to delete it. Let the compiler tell you if it really needs it.

The insight: Can you really do it in a dynamic language (SmallTalk, Ruby and the rest of the gang)? Would you 100% trust some tool saying that your Smalltalk program does not use a certain class?

2 comments :: Safe and easy elimination of dead code

  1. ... except, of course, if your code uses Reflection, or instances are created using tools such as Spring's Bean factory (which uses reflection), etc. In all these cases, Java == Smalltalk from this post's point of view.

  2. I have read your blog its very attractive and impressive. I like it your blog.

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