Software Architect's Handbook

Duplicate code

Duplicate code is identical (or very similar) code that exists in multiple places. The parts of your codebase that are duplicated violate the Don't Repeat Yourself (DRY) principle. As we learned in Chapter 6, Software Development Principles and Practices, following the DRY principle means eliminating duplication in our codebase. Duplication of code is wasteful and makes the code more difficult to maintain. Some of you may have had the experience of needing to make the same code change in multiple places because of duplicate code.

Any instances of duplicate code should be abstracted out and placed in a single location. All of the places in the codebase that need the logic can then be routed through the abstraction. Eliminating ...