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Top 30 Core Java Interview Questions and Answers

12/Jul/2021 | 5 minutes to read


Here is a List of essential Core Java Interview Questions and Answers for Freshers and mid level of Experienced Professionals. All answers for these Core Java questions are explained in a simple and easiest way. These basic, advanced and latest Core Java questions will help you to clear your next Job interview.

Core Java Interview Questions and Answers

These interview questions are targeted for Core Java. You must know the answers of these frequently asked Core Java interview questions to clear the interview.

1. Explain something about Java.

2. What is Bytecode in Java?

3. What is the use of wrapper class in Java?

4. What is a Just-in-time (JIT) compiler?

5. How will you differentiate ArrayList from Array in Java?

6. Explain method overloading and overriding in Java.

7. What is Deep, Shallow and Lazy copy in Java?

8. Explain Multithreading with an example.

9. Explain final, finally and finalize methods in Java.

10. Differentiate Comparable vs comparator.

11. Explain try, catch and finally.

12. How does a HashMap handle different collection items with the same hash code?

For more visit Different items with the same hash code.

13. Differentiate String, StringBuffer and StringBuilder in Java.

14. How will you differentiate Error and Exception?

15. Explain Exception Handling hierarchy.

16. How to throw a custom exception with an error object?

17. Differentiate HashTable and ConcurrentHashMap.

18. Explain NullPointerException in Java. How to fix it?

19. Explain the type of exceptions in Java.

20. Can we use a catch block without a try block?

21. Can we use a try block without a catch block?

Some General Interview Questions for Core Java

1. How much will you rate yourself in Core Java?

When you attend an interview, Interviewer may ask you to rate yourself in a specific Technology like Core Java, So It's depend on your knowledge and work experience in Core Java.

2. What challenges did you face while working on Core Java?

This question may be specific to your technology and completely depends on your past work experience. So you need to just explain the challenges you faced related to Core Java in your Project.

3. What was your role in the last Project related to Core Java?

It's based on your role and responsibilities assigned to you and what functionality you implemented using Core Java in your project. This question is generally asked in every interview.

4. How much experience do you have in Core Java?

Here you can tell about your overall work experience on Core Java.

5. Have you done any Core Java Certification or Training?

It depends on the candidate whether you have done any Core Java training or certification. Certifications or training are not essential but good to have.


We have covered some frequently asked Core Java Interview Questions and Answers to help you for your Interview. All these Essential Core Java Interview Questions are targeted for mid level of experienced Professionals and freshers.
While attending any Core Java Interview if you face any difficulty to answer any question please write to us at Our IT Expert team will find the best answer and will update on the portal. In case we find any new Core Java questions, we will update the same here.