12.1 Causes of Antipatterns

Every program, big or small, contains shortcuts, mistakes, and code that could have been thought out a little better. What distinguishes an antipattern from these errors is that, like a design pattern, it is repeated. When we explore the causes of antipatterns, we don't need to look at why they exist we need to look at why they persist and propagate. The main reasons that antipatterns spread are:

• Inexperience

• Unreadable code

• Cut-and-paste development

Inexperienced developers are the major cause of antipatterns. Obviously, newer developers are less likely to have come across these common mistakes previously, and are less like to recognize when they are making them. The danger of antipatterns is subtler when experienced developers use new technology. This danger is especially pronounced in J2EE technology, which evolves quickly, and in which many of the standard tutorials and code generation tools are full of antipatterns. To combat the problem, most organizations use training as well as code reviews with senior developers. But the best defense against antipatterns is to know your enemy: understanding and recognizing antipatterns is the key to avoiding them.

Unreadable code is another fertile breeding ground for antipatterns. Often, the existence of a well-known antipattern will be hidden because readers have to spend all their mental cycles trying to figure out what the code does, not why it does it. Developers sometimes favor conciseness and optimization over readability without taking into account the maintenance costs. Every shortcut that saves a few keystrokes or a few bytes of memory should be balanced against the costs in terms of developer hours and lost business when a hard-to-find bug is discovered. Unreadable code is best fought with consistency: publishing and enforcing code guidelines, relentless commenting, and aggressive review.

Cut-and-paste development refers to code that is taken from one place and pasted directly into another. Teams sometimes assume that cut-and-paste is a form of reuse: because the code has been used before, it is often considered more robust. Unfortunately, cut-and-paste actually makes code less reliable, since the pasted portion is used out of context. Even worse, bug changes don't propagate: changes to cut-and-paste code must be propagated manually. Cut-and-paste should only be necessary when entire objects cannot be reused. If you find yourself copying a particular piece of code, consider abstracting it and making it available to many classes through inheritance or as part of a separate utility class.