11 Exception Handling in Java Interview Questions

If you’re applying for a job programming or supervising others in Java development and coding, you may have to answer questions about Java exceptions, a powerful mechanism to ensure your program’s flow does not break in the case of exceptions. By reviewing some of the most common questions and answers about Java exemptions ranging from specific situations to general Java hierarchy questions, you can minimise stress going into your meeting while maximising your chances for success.

1. What is exception handling in Java?

Why your interviewer asks this: Your interviewer wants to ensure you understand the exception process and its importance. 

Provide a comprehensive answer, including the definition of an exception, which occurs when an event disrupts a Java program’s processes. Exception handling, an object-oriented process, allows you to ensure that those disruptions don’t prevent the program from completing its intended tasks. If one comes to mind, you can also provide an example, including any experience with different scenarios. 

2. Why does an exception occur?

Why your interviewer asks this: Your interviewer wants to understand whether you understand Java exceptions.

Exceptions can occur for various reasons, and you must know a few of them to include in your answer. For instance, exceptions and unexpected events happen due to incorrect user input, device failures, code errors, network errors, and resource constraints. Provide examples to solidify your thorough understanding with your interviewer. 

3. What is a finally block? 

Why your interviewer asks this: Your interviewer is testing your knowledge of different exception keywords.

In Java code, you use a finally block to execute the program regardless of whether you handle the exception. It always executes upon the try block’s exit. You should know when to use this block and in what cases it may or may not be suited to the code structure.

4. How are custom exception classes created?

Why your interviewer asks this: Your interviewer wants to know if you have the skills to create custom exceptions based on program needs.

An interviewer might ask you about creating a Java exception class because they’ve faced situations with an exemption that hasn’t existed in Java coding yet. The creation process for these exceptions depends on the type of custom exception needed. For instance, it’s possible to extend an extension class and have it checked or create an unchecked runtime exception.

5. Is a try block required before a catch block when coding Java exception handling?

Why your interviewer asks this: Your interviewer wants to know if you understand how to order blocks in your Java code properly.

Typically, you must follow a try block with a finally block, catch block, or both. However, more recent versions of Java may allow you to use the try block on its own with the AutoCloseable parameters or try-with-resources.

6. What types of exceptions get caught during compile time?

Why your interviewer asks this: Your interviewer wants to know if you understand checked exceptions.

Checked exceptions are exceptions caught during program compilation time and include several types. ClassNotFound exceptions occur when the Java virtual machine (JVM) can't find the classpath. Interrupted exceptions happen when the thread blocks input and output (IO) operations because it's otherwise occupied or sleeping. IO exceptions happen when IO operations fail. SQL exceptions trigger SQL database errors, and file not found occurs when the directory doesn't contain the file. Handle checked exceptions by coding a try-catch block to compile the full code successfully.

7. What best practices should you follow for exception handling in Java?

Why your interviewer asks this: Your interviewer wants to know if you have the experience and skills to perform at a high level with best practices.

This question is important if you're interviewing for a lead or supervisor role because you’ll be involved in designing and implementing best practices for your team. Below are a few suggestions for the answer. However, you’ll want to answer carefully and incorporate your experience and best practices.

• Avoid NullPointerExceptions by returning Boolean instead of null.

• Don’t use empty catch blocks; they create problems. Instead, use print stack trace or another command. 

• Default to unchecked exceptions unless you are very clear about why you need a checked one. Unchecked exceptions improve code readability.

8. What is Java exception chaining?

Why your interviewer asks this: Your interviewer wants to know whether you can use exception chaining to identify errors.

Exception chaining is when another exception is added to respond to an exception, creating an exception chain. This technique is mostly used for wrapping a checked exception into a runtime, unchecked, or RuntimeException. Using this technique, you should include the original exception so the handler code can access the root cause using the getCause() and initCause() methods.

9. What is your experience writing custom Java exceptions? How did you execute it? 

Why your interviewer asks this: Your interviewer is assessing how experienced you are in writing novel Java code exceptions.

To answer this question, describe the exemptions you’ve written and what you wrote them for. Remember, the interviewer asks if you understand how to write custom exceptions for different program requirements. 

10. How does the Java hierarchy work?

Why your interviewer asks this: Your interviewer wants to know whether you understand the exception hierarchy.

Potential employers often ask this interview question to determine if you understand the Throwable parent class and Error and Exception child classes. Errors terminate programs when system or resource (JVM) problems occur. Exceptions are abnormal conditions caused by program runtime errors. It’s the superclass divided into unchecked (runtime) and checked exceptions.

11. What are the Java exception handling keywords?

Why your interviewer asks this: The interviewer wants to know what exceptions you have worked with.

Interviewers ask this question to verify your Java exception vocabulary and gain insight into your experience with Java exceptions. When answering this question, include how you use try-catch, throws, throw, and finally blocks in your code. This is a great time to add examples of your previous projects and elaborate on your Java experience related to the job.  

Get started with Coursera

You can build your knowledge of Java and Java exceptions through online courses from top universities on Coursera. To begin building job-ready skills and enhance your Java expertise for any upcoming interviews, consider completing courses like Java Programming: Principles of Software Design from Duke University or the Object-Oriented Java Programming: Data Structures and Beyond Specialisation from the University of California San Diego—both on Coursera.