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25 Commonly Used Java Developer Interview Questions

Technical interviews are not about your formal education, but the skills and passion you have about the job. Having a diploma in computer science is excellent. The truth is companies are looking for something else these days: cultural fit and strong technical knowledge. Developers are assessed through a series of testing during the hiring process, both through interviewing and coding challenges. We want to help you understand this process and some of the most common Java interview questions in this post. 

Java Engineer Hiring Process

Companies are giving extra effort to optimize the hiring process to find the perfect fit. Working with different companies, we witnessed the best and the worst practices when it comes to the selection process. Typically, the steps would be: 

Prescreening 

Prescreening is a video or phone call to collect the necessary information about the candidate’s background. A recruiter may ask you about education, previous experience, motivation to change job, and salary expectations. This step is also essential to candidates. By asking the right questions, you can decide if this opportunity is right for you. It will save you time if you learn something about the company or the project that’s not on your plan. 

On-site interview

Once you passed the prescreening, the company wants to learn more about your technical and soft skills. The most common practice is to combine technical and HR interviews into one day, saving both your and the company’s time. If this is the case, prepare for both sides of the coin. Having a strong technical background is essential, but companies want to make sure that you can fit with the rest of the team well. Communication is a vital part of any software engineering team. You should pay attention to demonstrate your willingness to listen and provide feedback accurately during the whole process. Just as on any job interview, you will go through a few phases. 

Technical interview

Some of the technical questions will be questions about your tech knowledge and experience and how you perform specific professional responsibilities. These will not necessarily have a precise right or wrong answer. Others will be quiz-like questions. Many of these will have a clear answer. Some with a “yes or no” answer and others that require you to show your firm understanding of concepts. Some interviewers tend to jump into the technical interview right away. So, you may do only one or all of the following stages:

  • During the first phase of a conversation, interviewers want to get to know you better and present the company in the best possible way. They will ask you about your previous employment and projects, but they will also want to know if you fit in the company culture.
  • The second phase of the conversation is your time to shine and show what you know. In the technical interview, you will probably talk with another developer or project manager familiar with the development. They will ask you specific questions to evaluate your skills. 
  • In the final part, you can ask some questions about the job and the company. 

Final interview

This step is quite self-explanatory. The final meeting is the part where more hiring managers are involved in the hiring process. Their involvement is to validate the decision to proceed to the next phase with the candidate. 

The Offer 

Oh, that sweet, sweet call from a recruiter. Woohoo! You got the job. Now buy us some beer or just drop us a message if this post has helped you land that gig. Of course, this is the ideal scenario. Some companies have six or seven rounds of interviews, draining the life out of software engineers. Working with candidates, we understand how frustrating this might be. We hope you will have the patience to land that fantastic opportunity ahead. 

software developer selection process

The Basics of Computer Science – Algorithms and Data Structures

Here is the simple question for you – are you able to discuss algorithms? Algorithmic techniques and data structures are applied in solving programming challenges. Because of this, tech recruiters might test your knowledge of algorithms and data structures. Questions about algorithms and data structures are an excellent way for recruiters to find an intersection between practical experience and their talent.
Sometimes, not being able to answer a question won’t affect your performance. The hiring managers simply want to learn about your talent, but you should still prepare. Update your knowledge of basic algorithmic techniques for computational problems frequently arising in practical application. These may be sorting and searching, greedy algorithms, divide and conquer, dynamic programming. This step is especially useful for candidates with less experience and a great talent and understanding of computer science. Even if you don’t have a lot of experience, hiring managers can discover the potential for incredible achievements in you.

Questions about experience, skills, and personality

Employers ask candidates specific interview questions in every business. These differ from questions about you to your past work experiences. Make sure to exercise answering these popular questions since they will likely come up in an interview. Recruiters don’t want to scare you and start with serious questions straight away. They will first ask you about some basic stuff, and then go deeper into your knowledge. 

1. What programming languages have you used in the past? What are the programming languages that intrigued you the most?

It’s crucial not to lie when answering this question because they will ask you about the specific tasks that you had. A recruiter will try to find out if you’re familiar with a language they use at the company. Candidates should understand the technical stack and product of the company they’re interviewing with. An excellent answer to this question will link your previous experience to their tech stack. This way, you will showcase an understanding of how your role matches the bigger picture and helps the company grow. 

2. Do you prefer working in a startup environment or an established company? Why?

This question will show them if you’re the right fit for the company. Moreover, you have to ask yourself the same question before you apply for the job. You’ve probably done a bit of research about the company. Now all you have to do is to adapt your experience and knowledge to their expectations. 

3. What are the principles of good software engineering? What principles do you follow?

A recruiter wants to know more about your coding philosophy and critical thinking skills. Great programmers build code thoroughly, so it’s important to highlight how you logically organized system around a particular parameter. Highlight how you develop code that can be efficiently maintained and documented, and that you perform debugging as a part of the process. 

4. What distinguishes a great software engineer from a good one? Do you feel you have those qualities?

Well, you don’t want to brag, but… Just be honest, where are you when it comes to your skills, and where you want to be. Show a recruiter that you want to learn about the new technologies every day, that you’re aware that the learning process never ends. Be positive about your knowledge, but aware of your lack of expertise. Applicants should showcase their enthusiasm for development and talk about any projects they’re working on outside of a job. 

5. Are you familiar with the Agile software development process?

Nowadays, Agile is the most common methodology used to manage software development procedures. A recruiter may ask for your opinion about Agile. If a candidate hasn’t had experience with a particular methodology it won’t inevitably be a deal-breaker. Still, the candidate should be able to overcome that objection and demonstrate how they will familiarize themselves with the methodology required. Make sure that you’re at least familiar with agile terminology if you never had an opportunity to work in the company that used it.

Further, it’s essential to build an online presence and connect with other professionals from the field. Tech recruiters will Google you anyway, so why wouldn’t you make a great impression before they even meet you? Just update your LinkedIn and GitHub account regularly and delete projects that you don’t have the intention to finish. Also, do a bit of branding on other social media platforms. You have to make an effort to present yourself at your best. 

Core Java Interview questions 

Great Java developers are skilled in the implementation of object-oriented design patterns and can architect their code effectively in an OO way. If you’re not ready to discuss the latest features, you might have difficulty. Whether you are an experienced Java engineer, or just preparing for your entry-level job interview, Core questions play an essential role in Java/JEE interviews. We can divide the questions into these topics: 

  1. Java String Interview Questions
  2. Java Thread Interview Questions
  3. Java Collections Interview Questions
  4. Java Exception Interview Questions

Just like learning programming, preparing for technical interviews should take you back to the official documentation. You can find Java tutorials on the Oracle website. You probably know how often languages and frameworks are changing. Make sure to follow up on the most critical feature of different versions. You can also find precise answers to some of the basic questions, such as: What is an Object? 

Basic interview questions for Java developers

It can be easy to prepare for this kind of interview because companies usually focus on data structure and algorithms. 

  • It’s essential to know the right buzzwords, learn the right technologies, and prepare accurate answers to the commonly asked questions in Java interviews. 

So, go through data structure and algorithm and make sure that you know fundamental things. If you fail on basic things, you fail the interview. Many articles, books, and tutorials can help you prepare for the basic interview questions. Refresh your memory on stuff like a binary tree, queue, stack, linked list, and so on.

  1. Explain JDK, JRE, and JVM?
  2. Explain public static void main (String args[])
  3. Is Java a statically or dynamically typed language?
  4. What is the difference between an abstract class and an interface, and when would you use one over the other?
  5. How do you organize your class modules and assets?
  6. Why is Java not 100% Object-oriented?
  7. What are constructors in Java?
  8. What are the differences between Heap and Stack Memory?
  9. What is the difference between equals () and == ?
  10. What do you understand by the term ‘Functional testing’?
  11. Explain Bug cycle.

Advanced interview questions for Java developers

You may be an experienced Java developer, but that doesn’t mean that you shouldn’t prepare for an interview. Here are some questions that will help you test your knowledge.

  1. Based on which methodologies unit tests can be written? 
  2. How does Garbage Collection prevent a Java application from going out of memory?
  3. How is Java SE related to Java EE?
  4. Is ForkJoinPool introduced in Java 7 always a better alternative to ThreadPoolExecutor?
  5. What is the difference between HashMap, ConcurrentHashMap, and Map returned by Collections.synchronizedMap
  6. Servlets 3.0 introduced async support. Describe a use case for it.
  7. Why do you think lambda expressions are considered such a big thing for Java 8?
  8. Why would it be pointless for a static or final method to use dynamic binding?
  9. What will happen if you put System.exit(0) on try or catch block? Will finally block execute?

Prepare for the interview

No matter how great you are in your job, it’s necessary to prepare for the interview. In particular, you have to do a bit of research about the company. Please take a look at their website and learn more about the company culture, their projects, the technologies they use. You can also check glassdoor and see what commonly asked questions in the specific company are. Make sure what company offers matches your expectations as much as your skillset matches theirs. 

java developerinterview

We wish you luck on the Java interview!