Main image of article How to Become a Java Developer

Java, a programming language created in 1991, has stood the test of time. It regularly tops lists of the world’s most popular programming languages, and it’s a foundational programming language in thousands of organizations’ codebases. 

As the name suggests, Java developers are tasked with writing code in Java, supporting legacy systems (including debugging and testing), updating applications, modernizing codebases, and building new apps. Though it’s difficult to see how Java will leave us any time soon, diversifying a Java-heavy codebase will help it remain performant into the future.

Given Java’s use in Android, the world’s largest mobile operating system by market share, and its utility to the enterprise, the need for Java developers isn’t going away anytime soon. We spoke to experts in the field to find out what it takes to become a Java developer in 2023.

What Are the Mandatory Skills Java Developers Must Have?

Mark Bosma, VP of Talent for Torc, offers a list of key Java skills to learn:

Object-Oriented Programming (OOP) principles: Java is an object-oriented programming language, which means Java developers must have a strong understanding of OOP principles such as inheritance, polymorphism, encapsulation, and abstraction.

Integrated Development Environment (IDE): Java developers should have experience with an IDE such as Eclipse, NetBeans, or IntelliJ IDEA. An IDE is a software application that provides a comprehensive environment for coding, debugging, and testing Java programs.

Java APIs and Frameworks: Java developers should have knowledge of popular Java APIs and frameworks such as Spring, Hibernate, JDBC, JSP, and Servlets. These tools can help developers build scalable and efficient applications.

Database Management: Java developers must have a solid understanding of SQL and database management. They should have experience working with databases like MySQL, Oracle, or PostgreSQL.

Jason Clark, Principal Software Engineer at observability leader New Relic, tells Dice: “Java is an OOP language, so learning to express your ideas and designs with well-understood, clear and easy-to-test objects is a must-have. Always be studying how the libraries you use shape their objects, where things feel awkward and where they feel seamless, and apply that to your own code.”

The Java Developer Kit (JDK) has lots of built-in support and documentation, including extensive breakdowns of its libraries, which should give those new to the language a lot to explore. Microsoft also has a website featuring a series of short videos dedicated to the fundamentals of Java (as you might expect, much of the content focuses on how to use Java in conjunction with Microsoft’s tools and platforms, most notably Azure.)

Java features a “write once, run anywhere” (WORA) design, which means it can run on any device with a Java Virtual Machine (JVM). “Get deep visibility with tools like JFR (Java Flight Recorder),” Clark adds. “Knowing how your code is really running in detail is a huge advantage to a Java developer. The JVM has unprecedented levels of visibility available to you through standard tooling, but it takes some digging and time to get comfortable with them. Using these tools on your code routinely puts you in a good place when you need to look further to solve a complicated problem.”

No matter what your educational background or goals, a good grasp of Java fundamentals is critical; from there, shift your attention to the tools of your desired specialization. Simon Ritter, Deputy CTO of Azul, says: “For specific skills, it depends which area the developer will be focusing on. For enterprise back-end developers, things like Spring are essential and Jakarta EE to a lesser extent. The basic tools that get used all the time are as important as Java specific things. Knowing how to use GitHub, Maven (possibly Gradle) are vital for any modern project. If the developers are writing GUIs then JavaFX will be more important.”

Is a Formal Education Important for a Java Developer?

“Java development is very much like software development in many other programming languages, so a grasp of fundamental math is very useful,” Ritter adds. “I personally don't think you need to know things like calculus to write good Java code. It's more about having an analytical approach, which often gets developed through the study of math and sciences such as physics.”

Some Java experts don’t see a formal education as wholly necessary—so long as you’re willing to learn the necessary skills and put in the work. “A university diploma can help you ‘get your foot in the door,’ but I'm not sure I'd choose it if I had to start my career path over again,” says Dmytro Vezhnin, CEO and co-founder of CodeGym. “Most likely, I'd prefer self-learning, especially since many companies don't require a degree in CS from candidates. If you can solve a problem, it doesn't matter where and how you've learned that. If you are disciplined enough to study on your own, and you have a clear study plan (for example, if you enrolled in an online course or devised a plan with a mentor's help), you can become a developer much faster.”

Alex Sheplyakov, CTO at WiserBrand, says: “It is better to have a formal education than not to have it. At the same time, I never consider the presence of an engineering degree as a key decision-making factor when building development teams.”

What Stands Out on A Java Developer Résumé?

“For me, the core thing that usually stands out on a Java developer’s resume is their growth path,” adds Sheplyakov. “I mean such resumes that clearly show how a candidate's technical skills evolved over time, and what new technologies they learned step-by-step, moving from relatively simple tools to complex ones. What’s more, such a growth path may have nothing in common with moving from Junior to Middle and Senior Java developer. A candidate can be a confident Middle Java developer but be skilled with diverse Java tools and technologies.”

Vezhnin bluntly says he wants to see “a GitHub profile” on any developer’s résumé, but also says “’irrelevant’ experience is important, too, because it presents a candidate's soft skills. If they were successful at ‘irrelevant’ jobs in the past, they are likely to repeat this success.” A GitHub profile, sufficiently stocked with your projects and coding examples, can go a long way toward convincing a hiring manager or recruiter that you have the necessary skills to accomplish Java-related goals.

Bosma wants to see “experience with web development, database management, and code samples with links to their GitHub profile.” He also notes a good Java developer résumé should demonstrate teamwork; if you’ve worked on a team project, be clear about your contributions and how you worked with other stakeholders to meet critical milestones.

“The Java ecosystem is huge, so it doesn't work particularly well to treat frameworks as a checklist when reviewing a Java developer's résumé,” Clark notes. “I'm always looking to see when folks have used alternatives to the big projects (i.e., done web apps outside of Spring), or where they can demonstrate deeper knowledge of the frameworks they have used.”

Sample Interview Questions for Java Developers

We asked our panel for questions they might ask in a Java developer interview. Here’s the full list:

  • How is the JVM able to run and interoperate between multiple languages in the same application?
  • How does garbage collection work in the JVM?
  • What sort of symptoms would you expect to see if an application is having GC trouble, and how would you fix them?
  • What are the pros and cons of working with Java collections via the newer stream interfaces?
  • Can you explain the difference between a checked and an unchecked exception in Java?
  • How do you approach debugging a Java application, and what tools do you use to assist in the process?
  • What is the difference between an ArrayList and a LinkedList in Java, and when would you use each one?
  • Can you explain the concept of multithreading in Java, and how it can be implemented?
  • What is your experience with popular Java frameworks like Spring, Hibernate, or Struts?
  • what's your understanding of the OOP concept?
  • Can you explain the difference between an interface and an abstract class in Java?
  • What experience do you have with database technologies, such as JDBC, Hibernate or JPA?
  • Have you ever implemented or contributed to an open-source Java project? If so, can you describe your involvement and contributions?
  • What design patterns have you used in your Java development projects? Can you explain how and why you used them?
  • How do you ensure that your code is readable, maintainable, and scalable, especially as projects grow in complexity?
  • What is the main advantage of the OOP?
  • What principles of the hashes do you know?
  • What do you know about hashmaps?
  • What's the difference between an interface and abstract class?
  • Can we have a private constructor in a class? If yes, how will we create objects for that class?
  • What does it mean to code to the interfaces rather than concrete classes?
  • How do you adhere to the principle of loose coupling and high cohesion in Java?
  • How do you implement comparison of objects for your custom classes?

In addition to those questions, make sure to check out Leetcode if you’re preparing for a technical Java interview, as many organizations use Leetcode and similar sites as fodder for questions. If you’re preparing for an interview for an Android developer position, also make sure you know Kotlin in addition to Java, as the former is rapidly becoming a significant element in Android development.

In the meantime, reading Java threads and blogs might be your best method for staying up-to-date on all things Java. Courses are available online via platforms like Coursera or Udemy, and self-learners can find lots of documentation online to answer their most pressing questions.