Code Quality Basics - What Are Code Smells?

Image Image

In this article, we have a closer look at code smells. We see what they are, and what you should do about them.

You will learn

  • What Are Code Smells?
  • What are the typical code smells?
  • How do you identify code smells?
  • How do you react to code smells?

Free Courses - Learn in 10 Steps

Article Series

This is the sixth article in a series of eight articles on Code Quality

What Are Code Smells?

A code smell refers to a certain pattern in the code that signals there could be a defect lurking somewhere.

Static analysis tools are very good at detecting code smells. They analyze the patterns, and then see if they could lead to a problem.

For example, if you assign a variable in Java a null value, and then immediate call a method on it, a NullPointerException would result. That is nothing but a code smell!

If you do static analysis of that part of code, the tool would indicate there is a high chance of a defect in the code at that point.

Choosing static analysis tools is the best way to detect code smells in your application:

image info

SonarQube has great tools for detecting code smells. what we see in the snapshot above are the rules for Java, and a profile where there are 194 code smells present.

Typical Code Smells

What are examples of typical code smells? Let’s take the example of Java programs:

  • You make use of a deprecated method definition, that is annotated by @Deprecated
  • You make use of a for loop, but do not increment/decrement the loop counters
  • You access a static member using an instance variable
  • You make use of a switch statement, but do not have a default clause
  • You have a switch statement with just two case clauses
  • You call toString() on a String object
  • In a situation where you need to use a while loop, you use a for loop
  • You name a class as Exception, but do not extend the built-in Exception class, or a subclass of it
  • You throw an exception in the finally clause
  • You throw very generic exceptions
  • You use a try-catch block, where a try-with-resources might be a better option
  • You have unused private methods

When you see instances of such smells, you conclude that the developer does not fully understand what he/she was trying to do. Such situations could cause hidden bugs to exist in the code.

Other Kinds Of Code Smells

Other kinds of code smells could exists, especially in your JUnit code. These include:

  • Ignored unit tests
  • Empty test case
  • Test case without asserts

Handling Code Smells

Make sure that having zero code smells is an integral part of your Definition Of Done.

It is important that you do static analysis and manual code review on a regular basis.

Static analysis should be part of continuous integration build.

Do check out our video on the same topic:

image info


Code smells are patterns in code that could indicate hidden bugs. The two ways to detect code smells are static analysis, and manual code reviews. It is important to do both systematically, to keep the application free of code smells.

Related Posts

Docker Tutorial for Beginners - with Java and Spring Boot

Learn about Docker - What is Docker? Why Is Docker Popular? How to create Docker Image for a Java Spring Boot App?

Devops Tutorial | DevOps with Docker, Kubernetes and Azure DevOps

What is DevOps? How is it different from Agile? What are the popular DevOps Tools? What is the role of Docker, Kubernetes and Azure DevOps in DevOps. Let's get started with a simple usecase.

Deploy Java Spring Boot Applications to AWS, Azure, GCP with Docker and Kubernetes

In this article, we focus our attention on the cloud. How to learn the cloud and deploy Java Spring Boot Applications to AWS, Azure, GCP with Docker and Kubernetes?

Spring Boot Tutorials for Beginners

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. This resources will help you learn and gain expertise at Spring Boot.

Microservices with Spring Boot and Java - Part 1 - Getting Started

Let's learn the basics of microservices and microservices architectures. We will also start looking at a basic implementation of a microservice with Spring Boot. We will create a couple of microservices and get them to talk to each other using Eureka Naming Server and Ribbon for Client Side Load Balancing. In part 1 of this series, lets get introduced to the concept of microservices and understand how to create great microservices with Spring Boot and Spring Cloud.

20+ Spring Boot Projects with Code Examples

At in28Minutes, we have created more than 20 projects with code examples on Github. We have 50+ articles explaining these projects. These code examples will you learn and gain expertise at Spring Boot.

REST API Best Practices - With Design Examples from Java and Spring Web Services

Designing Great REST API is important to have great microservices. How do you design your REST API? What are the best practices?

Index - 500+ Videos

At in28Minutes, we are creating a number of tutorials with videos, articles & courses on Spring Boot for Beginners and Experienced Developers. Here's a list of video tutorials and courses for you

Creating Spring Boot and React Java Full Stack Application with Maven

This guide helps you create a Java full stack application with all the CRUD (Create, Read, Update and Delete) features using React as Frontend framework and Spring Boot as the backend REST API. We use Maven as the build tool.

Creating a SOAP Web Service with Spring Boot Starter Web Services

Let's learn how to create a SOAP Web Service with Spring Boot Starter Web Services. We will take a Contract First approach by definining an XSD and exposing a WSDL from it.


in28Minutes Best Selling Udemy Courses

Image Image Image Image Image Image Image Image Image

450,000 Learners are pursuing our 31 amazing courses and 6 Learning Paths. Start Now!

Join 450,000 Learners and 30+ Amazing Courses

LEARN DEVOPS - 200+ VIDEOS - Master DevOps with Docker, Kubernetes and Azure DevOps

350,000 Learners are learning everyday with our Best Selling Courses : Spring Boot Microservices, Spring, Spring Boot, Web Services, Hibernate, Full Stack React, Full Stack Angular, Python, Spring Interview Guide, Java Interview, Java Functional Programming, AWS, Docker, Kubernetes, PCF, AWS Fargate and Azure

85,000 Subscribers are learning from our Free Videos on YouTube : JSP Servlets, Spring, Spring Boot, Spring MVC, Hibernate, Eclipse, Maven, JUnit, Mockito, Full Stack - React, Full Stack - Angular, Docker, Kubernetes, AWS, AWS Fargate, PCF and Azure

Here are the recommend articles to read next : Spring Interview Questions, Spring Boot Interview Questions, Microservices, Hibernate, Spring Security, REST API with Spring Boot, Full Stack with React, SOAP Web Services, Exception Handling, Embedded Servers, Spring Data Rest, Spring vs Spring MVC vs Spring Boot, Building Web Application and Spring Data JPA.

You can checkout all our 100+ articles here - All Articles.

Do not know where to start your learning journey? Check out our amazing learning paths:
Learning Path 01 - Spring and Spring Boot Web Applications and API Developer,
Learning Path 02 - Full Stack Developer with Spring Boot, React & Angular,
Learning Path 03 - Cloud Microservices Developer with Docker and Kubernetes,
Learning Path 04 - Learn Cloud with Spring Boot, AWS, Azure and PCF and
Learning Path 05 - Learn AWS with Microservices, Docker and Kubernetes