51 Java Interview Questions To Expect (With Sample Answers)

By Indeed Editorial Team

Updated 1 September 2022

Published 29 September 2021

The Indeed Editorial Team comprises a diverse and talented team of writers, researchers and subject matter experts equipped with Indeed's data and insights to deliver useful tips to help guide your career journey.

After applying for a job as a Java programmer, a recruiter may contact you to schedule an interview for the position. To have a successful interview, it helps to review common Java interview questions. Knowing the questions an interviewer may ask can help you prepare answers that effectively highlight your skill level and experience with this high-level programming language. In this article, we list various Java programming interview questions recruiters may ask, including some with sample answers.

Related: How To Prepare for an Interview

General Java interview questions

At the beginning of an interview, a recruiter may ask general Java interview questions to get to know you, your personality and your specific career goals. Getting to know your personality makes it easier for them to assess your cultural fit with their company and how you'd fit with the other co-workers. This is the moment to show them a bit of charisma and make a good first impression. Here are some basic questions you may receive during a Java interview:

  • How would you describe yourself?

  • What are your strengths as a Java programmer?

  • What are your weaknesses as a Java programmer?

  • What do you know about our company?

  • Where do you see yourself in five or 10 years?

  • Why did you become interested in programming?

  • Why do you want to work for us?

  • Why should we hire you for this role?

  • What do you enjoy doing outside of work?

  • Why are you the best candidate for this Java programming job?

  • Why are you leaving your current job?

  • How soon can you start?

  • What is your expected salary range?

  • What do you enjoy doing outside of work?

  • Do you enjoy working with others as part of a team?

Related: Common Programmer Interview Questions (With Sample Answers)

Questions about experience and background

As the interview progresses, the recruiter may ask questions to get to know your unique Java experience. Understanding your relevant experience and background can help recruiters determine if you're able to perform the job's duties. Here are some questions an interviewer may ask to evaluate your experience and background with Java:

  • What are your contributions to a coding team?

  • Tell me about your duties in your last role as a Java programmer.

  • What are the different Java frameworks you've used?

  • Which Java tools are you skilled in?

  • How did you resolve a problem with a previous project? Explain the project and the process you went through to resolve the issue step-by-step.

  • Where did you receive your Java programming training?

  • What process does your current team use to complete projects? What would you change about the process and why?

  • Tell me about a time you showed initiative as a Java programmer.

  • How do you stay up to date on your Java programming skills?

  • How do you motivate yourself during complicated programming projects?

  • Why do you want to be a Java programmer?

  • What's the most important thing you've learned as a Java programmer?

  • Describe your greatest accomplishment as a Java programmer.

  • Describe how you complete a project from start to finish.

  • What's the most important thing you've learned as a Java programmer?

Related: What Are Competency-Based Interview Questions?

In-depth Java interview questions

Recruiters may ask in-depth questions that directly relate to the Java programming role you're interviewing for to assess specific knowledge. Additionally, it's possible that they ask situational questions that help them determine your personality and how you'd react during certain situations. Here are some in-depth questions you may receive during a Java interview:

  • Describe the differences between Java's sleep and wait methods.

  • Explain the steps for creating an Object class.

  • Why would you need to convert an Integer into a String?

  • Describe the difference between notify and notifyAll.

  • Why would you make a class private?

  • What would you do to find the Thread ID? Explain the process.

  • Explain the process you'd use to implement Quicksort in Java.

  • Tell me how you'd find the highest value in an array.

  • Detail the various ways to create a new file in Java.

  • Define a HashMap.

  • What do you consider to be Java's main features?

  • Explain what constructors are in Java.

  • How do equals() and == differ in Java?

  • Define wrapper classes.

  • What are JDK, JRE and JVM? Explain each thoroughly.

Related: 12 Important Interview Skills and How To Improve Them

6 Java interview questions with sample answers

Along with reviewing common questions you may receive during a Java interview, it's important to read sample answers to help you craft your own for the day of the interview. Reviewing sample answers can help you improve your answers before presenting them to the recruiter. Here are some interview questions you may receive for a Java programming role and examples on how to answer them:

1. Describe the difference between fail-fast and fail-safe iterators.

Employers may ask this basic question to gauge your Java proficiency. To answer the question, simply state the main difference between the two. You can also provide examples for a more comprehensive answer that showcases your knowledge.

Example: 'Fail-safe operates on a cloned copy, while fail-fast iterators operate directly on the collection.'

2. What are some differences between the most popular Java IDEs?

Since every company uses a different IDE, recruiters may ask this to determine your skill level with their own. Give a quick overview of some popular options along with their unique differences. You can also offer an opinion on which is your favourite.

Example: 'The Eclipse IDE is great for its collection of libraries. The Eclipse CHE edition is especially useful, as it allows you to work via a web browser. NetBeans is another good IDE, mainly for its cross-platform support and the visual debugger. The last IDE I'm familiar with is BlueJ, as this is the one primarily used in teaching. While I'm proficient with all of them, I'd say my favourite is NetBeans because of its unique features.'

Related: Integrated development environment: definition and types

3. Why can't you use tail recursion in Java?

A recruiter may ask you this to see if you know some of Java's limits. In your answer, explain why it doesn't work and how you can work around it.

Example: 'You can't use tail recursion because Java doesn't support it. If you aren't aware of this limitation, you may get a StackOverflowError. To solve this, use iteration instead.'

4. Why is it important to avoid calling abstract methods in your abstract classes?

When recruiters ask this, they're testing your Java knowledge. They're also trying to determine your ability to use critical thinking when creating your Java programmes. In your answer, clearly explain why it's best to avoid calling abstract methods in your abstract classes. You can also state the reason for the issue if you were to call them.

Example: 'It's best to avoid calling abstract methods in your abstract classes because it limits how you can implement those methods. The problem arises because of the initialisation order.'

5. Why can you run Java on any platform? Why doesn't this work in other languages?

As a Java programmer, it's good to know some of Java's advantages over other programming languages. Recruiters ask this to test your knowledge and determine whether you know what makes this programming language unique. In your answer, demonstrate that you know how Java works and why it's used.

Example: 'Java's known as an independent language, meaning you can use it on any platform, like Windows or Linux. This is different from platform-dependent languages, such as C++, which need to be ported every time. Java can achieve this because of the Java virtual machine and bytecode.'

Related: A guide to programming language popularity (with definition)

6. What's the basic difference between a List and a Set in Java?

Employers want to know that you're able to do things the right way when coding. While there are many ways to achieve the same end, some methods are better than others. Asking this question helps recruiters test your Java knowledge and abilities. In your answer, demonstrate that you know the basic differences between these similar elements in Java. Doing this also shows that you know how to do things the right way.

Example: 'A Set contains unordered elements and doesn't allow for repeated elements. If you try to insert a duplicate into a Set, it deletes an older element. In comparison, a List allows for duplicate elements, although listed in order. Therefore, if you need to maintain an order that allows for duplicates, it's best to use a List.'

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