Enhancing Code Quality through AI-Powered Metric-Driven Refactoring: A Multi-Model Analysis
TL;DR
Investigating LLMs as metric-driven refactoring assistants rather than code generators suggests that while LLMs are valuable assistants for structural improvement, their interventions require careful monitoring to avoid unintended trade-offs.
Abstract
: The growing adoption of large language models (LLMs) in software engineering has introduced new opportunities but also risks in the software maintenance lifecycle. While LLMs can generate entire codebases from natural language prompts, such automatically generated or rapidly prototyped code often accumulates structural debt, making systematic refactoring increasingly urgent. This work investigates LLMs as metric-driven refactoring assistants rather than code generators. Six models (ChatGPT, Claude, Gemini, Grok, DeepSeek, and Qwen) were evaluated on two types of Java projects: three controlled applications with manually inflated structural metrics, and three real-world applications from public GitHub repositories. Using MetricsReloaded in IntelliJ IDEA, we measured four CK metrics: complexity (WMC), cohesion (LCOM), coupling (CBO), and inheritance depth (DIT). Results indicate that LLMs significantly reduce complexity and coupling, improving class simplicity and modularity. However, cohesion improvements remained limited, with LCOM proving especially elusive. Inheritance depth showed strong reductions in synthetic high-metric applications but minimal change in real projects. ChatGPT produced the most consistent and structurally stable refactoring outputs in real applications, though occasional cohesion deterioration occurred. These findings suggest that while LLMs are valuable assistants for structural improvement, their interventions require careful monitoring to avoid unintended trade-offs.