Duplicated code

Let’s start with what Martin Fowler calls the stink parade (I can’t help but mention it because the term cracks me up) with duplicated code. Duplicated code is intuitively a bad smell, and our software engineer instincts will soon learn to reject it as something that harms us. Let’s try to list a few reasons why duplicated code is harmful to the health of our code bases.

Clearly, copy-pasting code is the first thing to avoid, at least in 99% of cases. Taking a piece of code from one class and using it exactly as it is in another is easily avoidable. By pausing for a moment to reflect, it’s highly likely that we can extract a method to use instead of the duplicated code. Centralizing the code in this way ensures better code maintainability. Just think about how nightmarish it would be to maintain (e.g., fixing a bug in) every single piece of copy-pasted code scattered throughout the code base (and the scariest part is that the developers...