As a moderator on the JavaRanch, I often come across posts asking how to reinvent features that are available in most application servers. In JDBC for example, I’ve had people ask how to implement their own database connection pooling and how to create their own JDBC driver. Often times the developer is trying to create something that already exists, but they are unsure how to use it. The general rule of thumb I tell programmers is, “If you feel like you are reinventing the wheel, you probably are”.

Review the API
If you ever get the feeling you are inventing the wheel, it’s a pretty good indication you are. In such situations, ask yourself “Is it likely a developer using the same component would need functionality X?”. If the answer is “yes”, then there’s a good chance there’s already such a feature in the API. Most often, reinventing the wheel comes from developers who are too lazy to review the API but not lazy enough not to rewrite the feature they think they are missing. Also, search the web. In some cases, you may need to download a new or updated library to get the feature you want, but this may give you access to even more features.

Your wheel isn’t better
Often called “Reinventing the square wheel”, it is likely the code you are recreating is worse, more buggy, and far less stable than the code you should be using. If you consider it for a moment, it makes sense a method built within the API should be better than a method built on top of the API. The API developer has access to private methods and objects that you do not have access to, and therefore your solution is limited by the public/external methods of the API. Furthermore, the fact the code is part of the API means scores of developers have hopefully reviewed the code for errors and performance enhancements.

That doesn’t necessarily mean the API implementation is better, but whenever I hear a developer say “I have a faster and cooler way of doing this than the way they do it in library” I cringe at the thought of what they may have written. If you do happen to create a better wheel, join the open source project and publish it for others to judge.

There’s always public humiliation
Many of the worst best articles that appear on the The Daily WTF come from programmers reimplementing the most basic functions of a language. One of the things that separates an experienced programmer from a beginner is the ability to recognize what tools in the API are needed for a task and how quickly they can be put together. And with that, I present a list of examples written by real developers and posted online for the world to see:

• Reinventing The Round
• Random Stupidity
• Right Under your Nose
• Validating Nothing
• To the Hexth Degree
• The Utility Package
• Perly Dates
• Enough String to Hang Yourself
• Printf to String

Any my personal favorite: I’ve heard from some good sources that the next version of SQL will use the word “GIMMIE” instead of “SELECT”