20 Advanced Core Java Interview Questions for Experienced Developers of 5 to 10 Years

These are difficult and advanced core Java questions for 5 to 10 years Experienced Java developers

Hello friends, if you are preparing for your next Java Developer interview and looking for Senior Developer or Team Lead position then you will have to prepare hard.

Earlier, I have shared 35 Java Questions, 15 Spring Framework Questions and 10 System Design Problem and in this article, I am going to share some advanced core Java interview questions for experienced programmers i.e. someone who has more than 5 years of experience in Java programming, mostly in core Java but JEE work is also fine.

I have found that once you become senior and your experience grows, you no longer see questions like String vs StringBuilder or Vector vs ArrayList, instead many companies ask about class loaders, Garbage collectors, concurrency and about JVM.

I have started collection some core Java questions for my preparation and today I am going to share some with you, I don’t have their answer, So, I am looking forward to you guys to answer them, of course only if you know.

By the way, if you are new to Java programming language or want to improve Java skills then you can also checkout following best Java courses to get better:

1. The Complete Java Masterclass (covers Java 17)
2. Java Programming and Software Engineering Fundamentals Specialization Certificate on Coursera
3. Java Programming Bootcamp: Zero to Mastery
4. The Complete Java Programming Masterclass! [Karpado]
5. CodeGym (learn Java by building Games)

These are my favorite online courses and platforms to learn Java from scratch and also build your Java skills. If you need more advanced courses to take your Java skill to next level you can also see following articles:

20 Advanced Core Java Interview Questions for Senior developers

Here are the 20 questions which I think every experienced Java developer should practice, they touches advanced topics like class loaders, garbage collection, performance, JVM internals, as well design patterns which are really crucial for Java developers.

1. What are classloaders and different types of class loaders in java?
2. You are using a third party library in your project which you think may be replaced in future with a new library, how will you code so that its easier to change the library in future?
3. You have two similar looking methods in your code where most of the logic is same except data set which is difference and there is a custom logic to convert that data into an object? How will refactor this code?
4. When does using Microservice architecture make sense and what are scenarios where a Monolith would be more appropriate than Microservices? (hint — latency)
5. What problem is solved by SAGA design Pattern in Microservices? What are alternatives?
6. What is Bootstrap class loader and how does it works?
7. What is Extensions class loader and how does it works?
8. What is application class loader and how does it works?
9. When an object becomes eligible for garbage collection?
10. Who performs garbage collection?
11. When does garbage collector run?
12. Which algorithm garbage collector uses to perform garbage collection?
13. List out different garbage collection algorithms?
14. Can we force JVM for garbage collection?
15. How to request jvm to perform garbage collection operation?
16. Explain the purpose of finalize method in relation to Garbage collection?
17. How many times finalize method is called on an Object?
18. Once an object is garbage collected can it become reachable again?
19. How to write a code that makes an object eligible for garbage collection?
20. What is difference between State and Strategy Design Pattern?

Java and Spring Interview Preparation Material

Before any Java and Spring Developer interview, I always use to read the below resources

Grokking the Java Interview

Grokking the Java Interview: click here

I have personally bought these books to speed up my preparation.

You can get your sample copy here, check the content of it and go for it

Grokking the Java Interview [Free Sample Copy]: click here

If you want to prepare for the Spring Boot interview you follow this consolidated ebook, it also contains microservice questions from spring boot interviews.

Grokking the Spring Boot Interview

You can get your copy here — Grokking the Spring Boot Interview

That’s all friends, these are a few Core Java Interview questions you can prepare for senior level Java interviews. As I said, these questions are mostly asked to experienced Java programmers so preparing them in advance is better.

Good luck for your Java Interview.

By the way, if you are new to Java programming language or want to improve Java skills then you can also checkout following best Java courses to get better:

1. The Complete Java Masterclass (covers Java 17)
2. Java Programming and Software Engineering Fundamentals Specialization Certificate on Coursera
3. Java Programming Bootcamp: Zero to Mastery
4. The Complete Java Programming Masterclass! [Karpado]
5. CodeGym (learn Java by building Games)

These are my favorite online courses and platforms to learn Java from scratch and also build your Java skills. If you need more advanced courses to take your Java skill to next level you can also see following articles: