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Essential Java Skills for Every Developer’s Career

By: Stella Aldridge
  |  May 1, 2023
Essential Java Skills for Every Developer’s Career

First introduced to the world back in 1996, Java today is still very much in demand. Over 35% of programmers worldwide worked in this language in 2021. Moreover, it is firmly among the three most popular programming languages in the TIOBE index.

What does it mean for you as a beginner Java developer? It means you’ll have to gain a competitive advantage to advance in your career successfully. Let’s take a look at the essential tech and soft skills you need to perfect.

Key Technical Skills for a Java Developer

What skills and knowledge should you have to get a job as a junior Java developer? What tools do you have to master to be able to move to the next level in your career? Which technologies do you absolutely have to study, and which ones are not as essential?

The answers to these questions largely depend on the company you aim to work for and its focus. But there are tech skills that are considered essential for every Java developer, beginner or advanced. Let’s find out what they are.

Core Java Skills

Core Java is the foundation of everything. If you are just starting your journey to becoming a Java developer, you can learn Java on Codegym, a practical online course that comes with over 1000 exercises and a friendly community. And if you have experience in Java programming, it is always a good idea to revise the basics, which Codegym is also great for. Of course, there are numerous other learning resources you can try. Just stick to the ones that focus on practice rather than theory only.

The most crucial core Java skills you need are:

Spring Framework

Spring framework is widely deployed these days. And no wonder. It allows building high-quality apps much faster. More and more companies appreciate its object injection capabilities, simplicity, elegant syntax and automation testing tools. So, if you want to advance in your career, you have to learn how to work with the following frameworks:

  • Spring Boot allows you to create cross-platform microservices
  • Spring MVC follows a Model-View-Controller architecture and is great for building web applications
  • Spring Clouds helps you quickly create robust cloud apps, so it’s essential in today’s cloud-based business environments

Testing Tools

Writing unit tests for your code is considered a good practice. Perfecting your unit testing skills will separate you from average developers and make you a rockstar. And embracing the Testing first philosophy will make you more productive and your code more stable. With solid testing skills helping you produce great code, you’ll spend less time troubleshooting and more time creating.

The most popular unit testing tools you need to familiarize yourself with are:

  • JUnit is considered to be the best library to start with, especially if you are entirely new to unit testing
  • Mockito is basically the standard library for creating mock objects in Java

APIs and Libraries

As one of the most popular and mature programming languages, Java has a vast ecosystem with numerous libraries and APIs. Leveraging these resources will enable you to do almost anything you need to do in Java. Great Java professionals know how to work with these tools flawlessly. Of course, you are not expected to know every API and every library backwards and forwards. But you do need to be familiar with the popular XML processing and unit testing libraries, as well as with the most crucial APIs:

  • Logging APIs are used in virtually every project, especially in server-side applications. Pay attention to the JDK’s own logging library and some great alternatives like Log4j, SLF4j, and LogBack
  • JSON Processing APIs, such as JSON.simple, GSON, Jackson and JSONP, are probably the most popular libraries for JSON processing in a Java environment
  • XML Processing APIs, like Xerces, JAXB, JAXP, Dom4j and Xstream, are just a few of the many XML parsing libraries you’ll want to learn
  • Collection APIs are important, and JDK comes with a rich collection library itself. But some third-party alternatives provide more options. Take a look at Apache Commons collections, Goldman Sachs collections, Google collections, Eclipse Collections and Trove
  • Date & Time APIs are also important, and JDK 8’s date and time API has you covered on Java 8 projects and onwards. But if you have to deal with older versions of Java, you’d better familiarize yourself with Joda-Time

JVM Internals

Understanding Java Virtual Machine and its architecture is important if you want to effectively use the Java ecosystem. You need to know what the various parts of JVM are, how all of them work, collectors, garbage collections, JVM options, etc.

While you are at it, learn to profile your applications and how to find the objects that take most of the memory and CPU.

Design Patterns and Architectural Patterns

Design and architectural patterns are tried and tested solutions to common problems. If you are able to flawlessly incorporate them into your work, you will make your code easier to change in the future. Proper use of Design and Architectural Patterns will improve the overall quality of your code, as well. So when someone new continues your work on the application, they will be able to understand your solution easily.

It is also a good idea to read up on the KISS, DRY and SOLID principles if you want to be able to write clean and readable code.

DevOps Tools & Hosting Systems

Strictly speaking, you do not have to be a professional DevOps engineer to be a good Java developer. But you need to be familiar with continuous practices, as well as how various tools and hosting systems work. So read up on general DevOps and practice working with these popular tools/systems:

  • Jenkins is the tool most everyone thinks of for monitoring a repeated task’s execution. Yes, it’s that popular, so make sure to try it out
  • Docker is a brilliant hosting system for assembling apps quickly using containers and is especially useful when collaborating with your team-members
  • Kubernetes is a another hosting system for managing complex containerized applications and is often used together with Docker

IntelliJ IDEA

IDEs are amazing tools that allow you to maximize your productivity. Good ones do the repetitive tasks for you while you focus on the fun stuff. You’ll need to be proficient in your IDE, and you will be working with IntelliJ IDEA. It is one of the most popular Java IDEs, so chances are your employer will require you to work in it.

Build Tools

Java build tools, or build automation software, allow you to automate parts of your work. Knowing how to work with these tools is essential. They will help you save time, highlight potential issues and generally make creating software easier. Maven and Gradle are the build tools considered most crucial for any Java developer.


You need to be familiar with the most popular version control system, and that’s Git. So learn to work with Git, and be sure to master the essential Git concepts and commands.

SQL and Databases

The more you know about databases, the better off you’ll be. And due its popularity, knowing SQL tops the list! With a solid understanding of SQL, you will be able to understand the store procedure and query DB, and as a result, improve your troubleshooting. All developers need to be able to determine if application issues are in your code or on the database layer. So mastering the basics of CRUD operations, joins, aggregations and indexing will help you a lot in your career.

Becoming a Rockstar Java Developer

Building a career in any field is a challenging endeavor. And for those looking to become a Java rockstar, you’ll certainly want to extend your skills into everything web related. Develop at least basic HTML, CSS and JavaScript skills, and build a solid foundation in Web Services, Web Server and Web App capabilities.

For now, you are equipped with the essentials you’ll need to perfect to become a great Java developer. So go ahead and study! Just don’t forget to practice, practice, practice. And always be sure to keep up with all the new developments, tools and technical advancements made to Java to help you grow and evolve.

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