Systematic literature review on software code smell detection approaches

Code smells are considered symptoms of poor implementation choices, which may hamper the software maintainability. Hence, code smells should be detected as early as possible to avoid software quality degradation. Unfortunately, detecting code smells is not a trivial task. Some preliminary studies investigated and concluded that machine learning (ML) techniques are a promising way to better support smell detection. However, these techniques are hard to be customized to promote an early and accurate detection of specific smell types. Yet, ML techniques usually require numerous code examples to be trained (composing a relevant dataset) in order to achieve satisfactory accuracy. Unfortunately, such a dependency on a large validated dataset is impractical and leads to late detection of code smells. Thus, a prevailing challenge is the early customized detection of code smells taking into account the typical limited training data. In this direction, this paper reports a study in which we collected code smells, from ten active projects, that were actually refactored by developers, differently from studies that rely on code smells inferred by researchers. These smells were used for evaluating the accuracy regarding early detection of code smells by using seven ML techniques. Once we take into account such smells that were considered as important by developers, the ML techniques are able to customize the detection in order to focus on smells observed as relevant in the investigated systems. The results showed that all the analyzed techniques are sensitive to the type of smell and obtained good results for the majority of them, especially JRip and Random Forest. We also observe that the ML techniques did not need a high number of examples to reach their best accuracy results. This finding implies that ML techniques can be successfully used for early detection of smells without depending on the curation of a large dataset.

Background Code smells are an indicator that something is misplaced in software systems, which can reduce maintainability and quality of software applications. In the literature, there is much research about code smells where numerous strategies for automating code smell detection have been developed to improve software quality. Objective The purpose of this work is to provide a review of search‐based, heuristic‐based, machine learning‐based, deep learning‐based, and hybrid‐based code smell detection algorithms. Method Concerning the main goals of this research, we have found 38 primary studies. We gathered relevant studies published on this topic between 2017 and 2024. These articles' data were extracted according to some criteria, including code smells, machine learning methods, programming languages, dataset size, evaluation strategy, and statistical tests. Results Machine learning‐based code smell detection methods have been suggested in most empirical investigations. We found that machine learning and deep learning are the most popular approaches for predicting code smells. Researchers typically employ support vector machine and decision tree algorithms. The Arcelli Fontana and Zanoni benchmark dataset was the most frequently investigated dataset. Most of the research community's attention has been focused on a small number of smells, including blob, feature envy, long method, and data class. Researchers also pay more attention to code smells like Long Method and Feature Envy. Deep learning techniques are increasingly used, and most scientists utilize source code metrics as indicators. The standard performance measurements mostly used are F‐measure, recall, and precision. Conclusions The study provides an overview of existing approaches and highlights current research trends in code smell detection, particularly the increasing use of machine learning and deep learning techniques.

Code smells are indicators of potential problems in software. They tend to have a negative impact on software quality. Several studies use machine learning techniques to detect bad smells. The objective of this study is to systematically review and analyze machine learning techniques used to detect code smells to provide interested research community with knowledge about the adopted techniques and practices for code smells detection. We use a systematic literature review approach to review studies that use machine learning techniques to detect code smells. Seventeen primary studies were identified. We found that 27 code smells were used in the identified studies; God Class and Long Method, Feature Envy, and Data Class are the most frequently detected code smells. In addition, we found that 16 machine learning algorithms were employed to detect code smells with acceptable prediction accuracy. Furthermore, we the results also indicate that support vector machine techniques were investigated the most. Moreover, we observed that J48 and Random Forest algorithms outperform the other algorithms. We also noticed that, in some cases, the use of boosting techniques on the models does not always enhance their performance. More studies are needed to consider the use of ensemble learning techniques, multiclassification, and feature selection technique for code smells detection. Thus, the application of machine learning algorithms to detect code smells in systems is still in its infancy and needs more research to facilitate the employment of machine learning algorithms in detecting code smells.

Are you smelling it? Investigating how similar developers detect code smells

Refactoring is the method to detecting and fixing bad smells in software. Refactoring techniques that have developed is a refactoring technique that is done on the source code. Along with the development of model driven software engineering (MDSE), it also developed the method of refactoring on the model. Refactoring method in the model is considered more effective and efficient because the detection and repair of bad smell is done at the design phase. The method of refactoring on the model evolves into a variety of techniques. Due to this, the systematic literature review is done to get the development of refactoring method on the developing model.

Code smells are specific patterns or characteristics in software code that indicate potential design or implementation problems. Identifying code smells has gained significant attention in software engineering. It is essential to address code smells to maintain high-quality software systems. Machine learning (ML) models, such as Long Short-Term Memory (LSTM), have been to detect code smells automatically based on source code features. However, the imbalanced distribution of code smells within software projects poses a challenge to the accuracy of these models. This study explores the role of data balancing methods in optimizing the accuracy of the LSTM model for code smell detection. We investigate different techniques for addressing the class imbalance problem, including random oversampling and synthetic minority oversampling techniques (SMOTE). We evaluate the performance of the LSTM model with and without data balancing methods using accuracy, precision, recall, f-measure, Matthew’s correlation coefficient (MCC), and the area under a receiver operating characteristic curve (AUC). Our experimental results, conducted on four code smell datasets (God class, data class, feature envy, and long method) extracted from 74 open-source systems, demonstrate the effectiveness of data balancing methods in improving the accuracy of the LSTM model for code smell detection. The results indicate that the use of data balancing methods had a positive effect on the predictive accuracy of the LSTM model. In addition, we compared our proposed method with state-of-the-art code smell detection approaches. The findings from the comparison indicate that our proposed method performs notably better than existing state-of the-art approaches across the majority of datasets.

The concept of code smells is widespread in Software Engineering. Despite the empirical studies addressing the topic, the set of context-dependent issues that impacts the human perception of what is a code smell has not been studied in depth. We call this the code smell conceptualization problem. To discuss the problem, empirical studies are necessary. In this work, we focused on conceptualization of god class. God class is a code smell characterized by classes that tend to centralize the intelligence of the system. It is one of the most studied smells in software engineering literature. A controlled experiment that extends and builds upon a previous empirical study about how humans detect god classes, their decision drivers, and agreement rate. Our study delves into research questions of the previous study, adding visualization to the smell detection process, and analyzing strategies of detection. Our findings show that agreement among participants is low, which corroborates previous studies. We show that this is mainly related to agreeing on what a god class is and which thresholds should be adopted, and not related to comprehension of the programs. The use of visualization did not improve the agreement among the participants. However, it did affect the choice of detection drivers. This study contributes to expand empirical evidences on the impact of human perception on detecting code smells. It shows that studies about the human role in smell detection are relevant and they should consider the conceptualization problem of code smells.

ABSTRACTInterest in the energy consumption of software has grown with rising energy costs and greater environmental awareness. Many approaches to research in this area have been proposed, from the examination of hardware and compiler optimizations to platform specific software modifications. However, the impact of general software design on energy efficiency remains unclear. The goal of this research is to summarize the findings of studies that empirically examine the impact of design patterns, code smells, and refactorings (which we collectively describe as design elements) on energy consumption. Our secondary goal is to provide an overview of the impact of these aspects of software design on energy performance and discuss the current state of the art. We present a systematic literature review (SLR) of papers that examine the impact of the aforementioned design elements on energy consumption. We perform a search through four major databases, a manual search through publications of eight conferences and five journals from 2010 through 2023, in addition to snowballing. We extract relevant data from the literature and present an overview of each experiment's setup, the data reported, and results for each design element studied. Beginning with a set of 8684 papers, we select 24 that include studies of these design elements. Overall, they provide data on 22 design patterns, 17 code smells, and 31 refactorings. Many studies are preliminary in nature, and contradictory findings are frequent. We present three main findings: (i) a wide array of design patterns, code smells, and refactorings have been examined from an energy performance perspective; (ii) many of these studies are preliminary in nature and indicate the need for further research; (iii) there has been little growth recently in publications empirically examining these aspects of software design.

리팩토링은 내부적으로는 시스템의 품질을 개선하고, 외부적으로는 시스템의 기능을 유지하는 일종의 소프트웨어를 변경하는 과정이다. 이러한 리팩토링을 적용하여 기존 소스코드를 개선하기 위해서는 개선할 사항이 무엇인지를 아는 것이 우선이다. 이를 위해 Martin Fowler와 Kent Beck은 코드속의 나쁜 냄새(코드스멜)를 식별할 수 있는 방법을 제시 하였다. 또한 코드스멜을 탐지하고 어디에 어떤 리팩토링을 적용할 것인가를 결정하는 문제와 관련된 몇몇 연구가 발표되었다. 그러나 이러한 연구들은 코드스멜에 대한 명확한 표현이 부족하거나 한정된 코드스멜만을 탐지하는 단점이 있다. 그리고 리팩토링을 적용할 경우 행위보존을 위한 선행조건들의 표현방법이 리팩토링 절차에 포함되어 있거나 정형화되지 않아 행위보존의 모호함이 발생되는 단점을 가지고 있다. 이에 본 논문에서는 OCL을 이용하여 코드스멜의 정보를 정확히 명세화하고, OCL 번역기를 통해 코드스멜을 자동으로 탐지하여 리팩토링하는 프레임워크를 제안한다. 또한 적용사례를 통하여 자바소스코드속의 코드스멜을 OCL로 명세화하여 자동탐지하고, 리팩토링을 적용해 봄으로써 활용성과 효용성을 검증해본다. Refactoring is a kind of software modification process that improves system qualities internally but maintains system functions externally. What should be improved on the existing source codes should take precedence over the others in such a modification process using this refactoring. Martin Fowler and Kent Beck proposed a method that identifies code smells for this purpose. Also, some studies on determining what refactoring will be applied to which targets through detecting code smells in codes were presented. However, these studies have a lot of disadvantages that show a lack of precise description for such code smells and detect limited code smells only. In addition, these studies showed other disadvantages that generate ambiguity in behavior preservation due to the fact that a description method of pre-conditions for the behavior preservation is included in a refactoring process or unformalized. Thus, our study represents a precise specification of code smells using OCL and proposes a framework that performs a refactoring process through the automatic detection of code smells using an OCL interpreter. Furthermore, we perform the automatic detection in which the code smells are be specified by using OCL to the java program and verify its applicability and effectivity through applying a refactoring process.

The threat situation due to cyber attacks in hospitals is emerging and patient life is at risk. One significant source of potential vulnerabilities is medical cyber-physical systems (MCPS). Detecting intrusions in this environment faces challenges different from other domains, mainly due to the heterogeneity of devices, the diversity of connectivity types, and the variety of terminology. To summarize existing results, we conducted a structured literature review (SLR) following the guidelines of Kitchenham et al. for SLRs in software engineering. We developed six research questions regarding detection approach, detection location, included features, adversarial focus, utilized datasets, and intrusion prevention. We identified that most researchers focused on an anomaly-based detection approach at the network layer. The primary focus was on the detection of malicious insiders. While several researchers used publicly available datasets for training and testing their algorithms, the lack of suitable datasets resulted in the development of testbeds consisting of various medical devices. Based on the results, we formulated five future research topics. First, the special conditions of hospital networks, the MCPS deployed within them, and the contrasts to other IT and OT environments should be examined. Thereupon, MCPS-specific datasets should be created that allow researchers to address the health domain’s unique requirements and possibilities. At the same time, endeavors aimed at standardization in this area should be supported and expanded. Moreover, the use of medical context for attack detection should be further explored. Last but not least, efforts for MCPS-tailored intrusion prevention should be intensified. This way, the emerging threat landscape can be addressed, IT security in hospitals can be improved, and patient health can be protected.

Copying and pasting program code fragments with minor changes is a common practice in software development. Software systems often have similar segments of code, called code clones. Due to many reasons, unintentional smells may also appear in the source code without awareness of program developers. Code smell may violate the principles of software design and negatively impact program design quality, thus making software development and maintenance very costly. This paper presents an enhanced approach to facilitate the process of identification and elimination of code smells. The proposed solution allows the detection and removal of code smells for refinement and improvement of the quality of software system. Code smells are analyzed, restructured and eliminated from the source code using reverse engineering techniques. The solution maintains the external behaviour of software system and judges the efficiency of systems code. An experiment has been conducted using a real software system, which is evaluated before and after using the approach. The results have been encouraging and help in detecting code smells.

A systematic literature review on software defect prediction using artificial intelligence: Datasets, Data Validation Methods, Approaches, and Tools

The quality of source code is negatively impacted by code smells. Since the term "code smell" originated, numerous attempts have been made to comprehend it by identifying it using various techniques, such as metric-based, heuristic-based, optimization-based, machine learning (ML)-based, etc. Among these, supervised machine learning (SML) has shown effectiveness in detecting code smells. However, SML techniques have significant limitations, including the dependency on expensive and high-quality labeled data, the need for representative training datasets, and the risk of introducing biases in labeled examples that lead to skewed predictions. To overcome these challenges, this study introduces a method that leverages unsupervised machine learning (UnML) along with feature engineering. Unlike SML, UnML does not require labeled data and minimizes potential biases. The proposed method was evaluated using four datasets containing different types of code smells and was compared with a previous study that used SML techniques. The results indicate that the UnML-based method is effective, achieving outcomes closely aligned with those from the SML approach. This method is especially beneficial in situations where labeled data is scarce or unavailable and can be used to identify new code smells, generate labeled data for SML and detect multiple code smells simultaneously within a codebase.

Digital transformation in the field of education demands continuous innovation in learning processes, particularly in informatics courses that emphasize the mastery of computational thinking and programming skills. One widely developed approach is gamification, which refers to the integration of game elements into learning contexts to enhance students’ motivation and engagement. This study aims to analyze trends, dominant elements, platforms used, impacts, and future development directions of gamification-based informatics learning systems through a Systematic Literature Review (SLR) method. The research methodology follows the PRISMA guidelines, encompassing stages of literature identification, title and abstract screening, full-text eligibility assessment, as well as data analysis and synthesis. A total of 24 articles were identified in the initial search and subsequently selected based on predefined inclusion and exclusion criteria, resulting in 10 articles for in-depth analysis. The PICOS framework was employed to clarify the scope of the review, including informatics learners as the population, gamification as the intervention, conventional learning as the comparison, and outcomes in terms of motivation, engagement, and learning achievement. The findings indicate a significant increase in the implementation of gamification in informatics education over the past five years. The most dominant gamification elements identified are points, badges, levels, and leaderboards, with web-based e-learning platforms serving as the primary medium for implementation. Overall, gamification has consistently demonstrated positive effects on students’ motivation, engagement, and learning outcomes. This study concludes that gamification holds strong potential as an effective and sustainable learning strategy to support digital transformation in informatics education.

This research investigates the impact of prompt engineering on the efficiency, code quality, and security of CRUD (Create, Read, Update, Delete) operations in software development using large language models (LLMs) like ChatGPT. Prompt engineering, which involves crafting specific inputs to guide AI outputs, has become crucial for code generation, debugging, and vulnerability detection tasks. The study addresses three key research questions: identifying the most influential aspects of prompt engineering on CRUD efficiency compared to traditional coding, recognising common error patterns in AI-generated code and preemptive mitigation strategies, and leveraging human-AI collaboration to optimise CRUD application development. This study evaluates 52 relevant papers from 2018 to 2023 through a systematic literature review from Google Scholar, ResearchGate, arXiv, and Sci-Hub. The findings indicate that effective, prompt engineering significantly enhances productivity, reduces development time, and improves code adaptability to complex data structures. Techniques such as role-prompting and chain-of-thought prompting are highlighted for their ability to produce high-quality code, reducing errors and enhancing overall code quality. The review revealed significant results, including identifying prompt engineering techniques that substantially improve the performance of LLMs in CRUD operations. ChatGPT, in particular, excels in generating and debugging code but struggles with more complex tasks and security vulnerabilities. The study emphasises the need for continuous human oversight to ensure security and correctness, addressing challenges such as managing programming variability and the stochastic nature of LLMs.The research concludes that integrating ChatGPT into CRUD operations significantly advances software development, improving efficiency, code quality, and security. However, it is crucial to address its limitations through better prompt engineering and continuous human involvement. Future work will involve developing a fully functional CRUD application using generative AI, further evaluating its practical applications and limitations in software development.