10 Java Interview Questions and How to Answer Them

Interviews for Java development roles typically concentrate on technical skills and explore workplace skills like problem-solving and teamwork. In this article, explore various categories of questions you might encounter to help you prepare for your Java interview.

Java interview: What to expect

Considering a specialized role in Java development can be a strategic career move. Java developers in the US earn an average annual salary of $96,278, making it a financially rewarding field [1]. In addition, a Stack Overflow survey from the same year underscores the prevalence of Java in tech fields, ranking it among the most widely used programming languages. This suggests not only sustained industry relevance but also opportunities for career growth [2].

When looking for a role in Java development, hiring professionals often look for a mix of technical and workplace skills. While the exact skills hiring managers are looking for will vary depending on the position and company needs, some common technical skills sought after include: 

• Object-oriented programming

• Java testing tools

• Machine learning

• Artificial intelligence

• DevOps tools

In addition to strong computer skills, hiring managers will look at how you will fit into their team and work culture. Desirable people skills include:

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• Effective teamwork skills

• Adaptability

• Communication

• Problem-solving

10 Java interview questions

Proper preparation is one key to a successful job interview. Knowing how to navigate different questions, understanding the company’s culture, and being aware of your expectations can set you apart from other candidates. To prepare for interviews, practicing answers to technical and personal questions can help you ace them. Consider the following questions when getting started.

1. What is Java, and what are its features?

What they’re really asking: Can you articulate why Java is a powerful language for our projects?

When asked this question, the employer wants to gauge your understanding of Java and how its features can benefit their projects. You might choose to discuss how Java’s platform independence, object-oriented programming, versatility, and memory management can elevate the types of projects the company works on.

The interviewer might also ask:

• What features of Java make it a good choice for the company’s projects?

• Which features of Java do you use most often?

2. What is the advantage of Java compared to other programming languages?

What they’re really asking: Why should we continue to invest in Java technology as opposed to other languages?

The employer wants to understand your perception of Java’s advantages over other codes. You can use this question to discuss past projects and why you chose Java for the task. Highlight Java’s ability to run on any platform. This “Write Once, Run Anywhere” capability is a significant advantage for companies looking for platform-independent solutions.

If asked specifically about Java compared to other popular languages, such as C++ or Python, it would be good to know some key differences. For example, Java is an object-oriented, high-level interpreted program, while C++ is a procedural, middle-level compiled language. Java and Python are both high-level, interpreted languages. However, beginners and those in website design or data analytics often choose Python, while network computing and desktop operations professionals often use Java. 

The interviewer might also ask:

• Why do you choose to code with Java?

• When would you choose Java over Python or C++? 

3. What are Java variables?

What they’re really asking: Do you understand the fundamentals of Java?

Java variables are essentially named storage units representing a certain value or range of values. These variables are stored in the program memory and are manipulated within the code. When answering this question, you should reference local, instance, and class variables to show comprehensive understanding. Here is an explanation of each variable:

• Local variables exist within a certain method or unit of code and are then destroyed. 

• Instance variables exist outside methods but within classes. 

• Class variables, or static variables, are constant variables that can be called and declared at any point within the code.

The interviewer might also ask:

• When would you use each type of variable?

• Can you describe a time you defined a class variable?

4. What is an exception? 

What they’re really asking: Do you know how to design code to handle unexpected scenarios?

Exceptions are errors that cause the code flow to go off the intended course. Java has many ways to handle exceptions, including built-in exception-handling features. Sometimes, you can create custom exceptions to handle specific errors that are more likely in your user base. Employers may look to evaluate your capacity for writing clean, specialized code that fits their project’s unique requirements, including knowing what exceptions are and how to handle them. When answering this question, showcase your knowledge of an exception, how built-in features support exception handling, and what custom exceptions might be needed in their applications. 

The interviewer might also ask:

• What are the best practices for writing custom exceptions?

• How do you preemptively design code to handle exceptions? 

5. What is aggregation?

What they’re really asking: Can you create Java code that goes beyond basic functions?

In Java coding, aggregation represents the relationship between an object or classifier and the variables or objects within this classifier. For example, you might have an object labeled “Math” aggregated to an object named “Subjects.” Other objects with an aggregate relationship to “Subjects” might include “Science,” “English,” or “History.” Demonstrating you know how to use aggregation within your Java code can demonstrate knowledge of advanced or organized coding practices.

The interviewer might also ask:

• What is an example of a time you used aggregation?

• When might aggregation be flawed?

6. How do you navigate having several Java projects at once?

What they’re really asking: Can you handle multiple projects at the same time?

Employers want to know if you’re organized and can handle multiple projects efficiently. Discuss your past project experience and understanding of Agile methodologies to show your commitment to ensuring every project is well-managed, from setting timelines to allocating resources and prioritizing tasks.

The interviewer might also ask: 

•  How do you produce quality code when you have several projects at once?

• Are you comfortable with multitasking?

7. What is your development process when entering an existing project?

What they’re really asking: Can you integrate seamlessly into our ongoing projects and contribute effectively?

The employer wants to know if you can effectively enter an existing Java project. Discuss your approach, from the initial code review and understanding of the project architecture to asking for assistance and identifying areas for improvement. Emphasize your commitment to understanding the existing code base and aligning with the team’s objectives. You can also use this question to highlight your communication skills.

The interviewer might also ask:

• How do you assess project needs when you first join an existing project?

• Can you give examples of how you improved an existing project after joining it?

8. How do you keep your code organized?

What they’re really asking: Can you produce code that is easy for others to understand and maintain?

The employer wants to know how well you can write and organize code, with an eye towards long-term maintainability. Explain your strategies for code organization, including how you make it easier for other people to work with your code by adding comments or organizing it a certain way. Mention how organized code reduces debugging time and makes it easier for teams to collaborate, which benefits project timelines.

The interviewer might also ask:

• Do you use any tools or specific methodologies for code organization?

• How do you ensure other programmers can read your code?

9. Can you give an example of working on a team?

What they’re really asking: How well do you collaborate with others, and what positive impact does your team involvement have on projects?

When an employer asks this question, they want to assess your teamwork skills and how you contribute to a group dynamic. Discuss a specific example where your teamwork led to a successful project outcome. Highlight your role in the team and relate it to how you could benefit the company’s projects.

The interviewer might also ask:

• How would you share code effectively within a team? 

• Can you share an example in which your team had to work quickly to meet a deadline?

10. How do you stay current with technical knowledge?

What they’re really asking: Are you proactive about keeping your skills up-to-date, and how will that benefit our projects?

The employer wants to assess your commitment to staying current with new technologies and methodologies. Discuss your strategies for continually updating your skills, such as reading blogs, attending conferences, or taking online courses. Make it clear that by staying up-to-date, you are better positioned to bring innovative solutions to the company’s projects.

The interviewer might also ask:

• What is a new skill you’ve learned in the past year?

• Do you participate in any developer communities or forums?

Questions to ask the interviewer

Asking the interviewer questions is a great way to show interest in the position, demonstrate your research, and help decide whether this position is the right fit. These questions give you, the candidate, a deeper understanding of the role, the work environment, and what the employer finds fulfilling about being part of the organization. Some questions you might consider include the following.

1. What skills are you seeking in a top candidate for this position?

This question clarifies the skill set the employer values most. It can help you determine whether you’re a strong match for the job.

2. How would you describe a typical workday?

This gives you insight into the daily expectations and how the team operates, setting the stage for how you would fit into the workflow. If you have a specific work style or workflow you are looking for, you might want to discuss your expectations during this conversation. 

3. What do you find most satisfying about being part of this organization?

This question can help you gauge the company’s culture and whether it aligns with what you find meaningful in your career. 

4. Does the company offer career development opportunities? 

This question can give you an idea of what direction your potential employer would see you developing and what opportunities are available to strengthen and develop your skill set. This can also help you decide if this is a long-term role for you and how to weigh the potential benefits of this position.

5. What is the team structure of the IT department? 

Understanding how an organization assigns tasks and runs operations gives you a feel for where you would fit into the existing structure. 

Preparing for the interview

Employers use Java interviews to evaluate your technical expertise and gauge your communication skills, professionalism, and overall potential contribution to the organization. As a candidate, you should view the Java interview as a two-way street: it lets you ascertain if the role aligns with your professional interests, skills, and long-term career goals.

Prepare to answer introductory questions. 

Introductory questions like “Tell me about yourself” or “Why are you interested in this position?” are typically the gateway to the interview. These questions offer an opportunity to set the tone for the following conversation. To prepare, consider formulating concise and informative responses that align your experience, skills, and career aspirations with the role you’re applying for. Practicing these responses can help you start the interview on a strong note.

Practice your responses using the STAR method.

Behavioral questions are common in many job interviews. These questions ask you to discuss your experiences and how you acted in these scenarios. To structure your responses effectively, employ the STAR method, which stands for Situation, Task, Action, and Result. This method enables you to present clear and detailed examples in an organized manner. Practice crafting responses using the STAR method to various common behavioral questions to enhance your readiness.

Research the company.

Go into an interview with a solid understanding of the company where you seek employment. Employers often look for employees who care enough to research the company’s mission and values.

Know your salary expectations.

If an interviewer asks you about salary expectations, you should have a number in mind that you can provide to your prospective employer. To determine this number, take time to calculate what income you need to live comfortably, what comparable roles are offering, and what salary range you would be comfortable accepting.

Getting started with Coursera 

To continue enhancing your technical Java skills, you can take several online courses from universities through Coursera. Start with Algorithms, Part 1 by Princeton University to build your foundation. This program covers topics like analysis of algorithms, stacks, quicksort, and more. Upon completion, gain a shareable Professional Certificate to include in your resume, CV, or LinkedIn profile.