Java Developer Interviews

Java Developer Interview Questions

In your interview for a java developer position, be prepared to answer technical questions that test your understanding of Java basics. Interviewers may also ask open-ended questions to assess your coding and problem-solving abilities. Prepare for non-technical questions that focus on time management, interpersonal communication, and work ethic.

Top Java Developer Interview Questions & How to Answer

Question 1

Question #1: What is the difference between HashTable and HashMap in Java?

How to answer
How to answer: Interviewers use technical questions to assess your formal training and understanding of the Java programming language. Use your answer to demonstrate your communication skills. Even if you have been coding for some time, it can be helpful to review Java basics before your interview.
Question 2

Question #2: Write a program to determine if 243 is an Armstrong number.

How to answer
How to answer: Interviewers use open-ended questions to test your coding skills. This question allows the employer to assess your ability to solve a problem using a Java algorithm. Explain your thinking process as you use a code editor or whiteboard to solve the problem.
Question 3

Question #3: How do you produce quality code when you have several Java projects to complete at once?

How to answer
How to answer: Java developers often juggle multiple projects at the same time. Interviewers use questions such as this to test your time management and organizational skills. Employers are also trying to assess your commitment to quality work. If you have experience as a developer, include examples from your work history that demonstrate high-quality work and effective time management.

30,900 java developer interview questions shared by candidates

I had to work on a codebase with a model class, a service interface and a third class with some business logic based on the other two. There were some missing names, logic, etc. The purpose of the interface and the business logic class were provided in javadoc style comments.
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Associate Java Developer

Interviewed at Wise

3.6
Jan 22, 2022

I had to work on a codebase with a model class, a service interface and a third class with some business logic based on the other two. There were some missing names, logic, etc. The purpose of the interface and the business logic class were provided in javadoc style comments.

Circuit breaker implementation in Java: The service A calls service B and service C every time. If one service fails 3-times in 10 minutes ( or 20 seconds in the implementation) the next call will be blocked for 5 minutes (10 seconds in the implementation). There was given a simulation of remote method calls, I needed to implement only the execute() which calls the remote service if possible.
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Senior Backend Java Engineer

Interviewed at Wise

3.6
Feb 19, 2026

Circuit breaker implementation in Java: The service A calls service B and service C every time. If one service fails 3-times in 10 minutes ( or 20 seconds in the implementation) the next call will be blocked for 5 minutes (10 seconds in the implementation). There was given a simulation of remote method calls, I needed to implement only the execute() which calls the remote service if possible.

What is exception? when should occur NullPointer exception?write a program for NullPointerException? explain about singleton design pattern? Write a thread safe Singleton class. can we write a class in scriptlet? Expalain abou Hashset?
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Java Developer

Interviewed at Dell Technologies

3.7
Jul 23, 2016

What is exception? when should occur NullPointer exception?write a program for NullPointerException? explain about singleton design pattern? Write a thread safe Singleton class. can we write a class in scriptlet? Expalain abou Hashset?

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