Building Maintainable Software, Java Edition

Preface

In der Beschränkung zeigt sich erst der Meister. (In simplicity one recognizes true skill.)

J.W. von Goethe

After 15 years of consulting about software quality, we at the Software Improvement Group (SIG) have learned a thing or two about maintainability.

First, insufficient maintainability is a real problem in the practice of software development. Low maintainability means that developers spend too much time on maintaining and fixing old code. That leaves less time available for the most rewarding part of software development: writing new code. Our experience, as well as the data we have collected, shows that maintaining source code takes at least twice as long when maintainability is measured as below average, compared to when maintainability is above average. See Appendix A to learn how we measure maintainability.

Second, lack of maintainability is to a large extent caused by simple issues that occur over and over again. Consequently, the most efficient and effective way to improve maintainability is to address these simple issues. Improving maintainability does not require magic or rocket science. A combination of relatively simple skills and knowledge, plus the discipline and environment to apply them, leads to the largest improvement in maintainability.

At SIG, we have seen systems that are essentially unmaintainable. In these systems, bugs are not fixed, and functionality is not changed or extended because it is considered too time-consuming and risky. Unfortunately, ...