Rule of Three
The Rule of Three is a software development principle that suggests code duplication should be refactored into a reusable abstraction after it appears three times. It serves as a heuristic to balance the trade-offs between premature abstraction and excessive duplication, promoting maintainable and DRY (Don't Repeat Yourself) code. This rule is commonly applied in refactoring and code review processes to guide when to extract common logic.
Developers should learn and apply the Rule of Three to improve code quality by avoiding both unnecessary complexity from early abstractions and the maintenance burden of duplicated code. It is particularly useful in agile development environments where requirements evolve, as it helps decide when to invest in refactoring based on actual usage patterns. Use cases include refactoring repeated functions, classes, or patterns in languages like Java, Python, or JavaScript to enhance readability and reduce bugs.