Refactoring is a disciplined technique for restructuring existing code by applying small, behavior-preserving transformations to improve its internal structure without changing external behavior. Popularized by Martin Fowler's catalog, refactoring addresses code smells — symptoms of deeper problems like duplicated logic, unclear naming, or tangled dependencies — with systematic, named techniques that each tackle a specific design weakness. The practice relies on comprehensive automated tests as a safety net, enabling developers to continuously improve code readability, maintainability, and adaptability. Understanding when and how to apply each refactoring, along with recognizing the smells that trigger them, transforms chaotic codebases into clean, flexible systems without risking functionality.

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