6 Java Support Interview Questions (With Sample Answers)

Updated 23 March 2023

Java is a high-level, object-oriented programming language that developers use to build mobile, cloud, web and game applications. People in Java support roles debug and resolve software issues and production failures and monitor and tune application performance. When preparing for an interview for a Java support engineer position or a similar role, it is helpful to learn about frequently asked questions and how to answer them. In this article, we list some Java support interview questions with sample answers and provide tips to help you prepare for your next interview.

Please note that none of the companies, institutes or organisations mentioned in this article are associated with Indeed.

6 Java Support Interview Questions And Sample Answers

Java support interview questions include a combination of general and technical questions that assess your skills and work experience. The questions may focus on Java fundamentals, debugging, troubleshooting, memory management, garbage collection and Java frameworks. Here are some questions and sample answers to guide you:

1. Explain the purpose of exception handling in Java and the different types

Interviewers may ask this Java support interview question to assess your basic knowledge of the Java exception-handling mechanism. Mention what exception handling is and explain its types and how they are used. Also, try to provide some examples in your answer.

Example answer: Exceptions are unexpected events, such as invalid user input, network issues and device failure, that can cause the application to terminate abruptly. In the case of an exception, the Java method creates an exception object and sends it to the JVM. The exception object contains information about the type of exception and the status of the program when the exception occurred. This helps programmers debug the code and identify the error at a later stage. Checked and unchecked exceptions are two types of exceptions in Java.

Checked exceptions are predictable but unpreventable errors that can occur due to a lack of system resources, an incorrect file path or the failure of input-output operations. Unchecked exceptions arise due to an error in program logic or a bug in the code. In the first case, a programmer can include exception-handling statements based on exceptions that may occur during program execution. In the second case, the programmer can view the logs to identify the error and make changes to the code.

2. What is the difference between deadlock and livelock in Java?

Deadlocks and livelocks can result in systems becoming unresponsive and failing. Interviewers ask this question to assess your understanding of concepts, such as resource allocation, synchronisation and concurrency, and your approach to resolving them. Mention key differences between the two terms and list some techniques you can use to prevent them.

Example answer: Both deadlock and livelock are common problems in multithreading and can result in performance issues. Deadlock is a situation where two processes enter a waiting state because each has a resource that the other requires. This results in the blocking of both processes indefinitely. Livelock differs from a deadlock in that the processes keep changing their active states in response to each other instead of blocking each other indefinitely.

For example, consider two processes, A and B. A has resource Y that B requires, and B has resource X that A requires. Each process requires both resources to complete its execution. In the case of a deadlock, A keeps waiting for B to release X, and B keeps waiting for A to release Y. This results in the processes blocking each other. In the case of a livelock, A releases Y to help B complete its execution and B releases X in response to A. Because each process requires both X and Y, neither can finish their execution.

3. What are memory leaks? How do you diagnose them?

Memory leaks can cause an application to consume more memory, resulting in reduced performance. Interviewers ask this question to evaluate your understanding of memory management in Java. Define what a memory leak is and list the techniques you might use to diagnose and resolve it.

Example answer: Memory leaks occur when the garbage collector is unable to recognise unused objects and they remain in memory indefinitely. This reduces the available memory for other objects and usually results in an OutOfMemoryError exception. Some causes of memory leaks include the creation of unnecessary objects, excessive use of static objects, failure to clean up native system resources without an in-built garbage collection mechanism and bugs in third-party applications. Developers can use third-party applications to conduct static analysis and detect memory leaks.

Some best practices to prevent memory leaks include having proper object references, using try-finally blocks, avoiding memory-intensive operations, using memory-efficient data structures and object pooling and monitoring memory usage.

4. How do you resolve the ClassNotFoundException in Java?

Interviewers ask about this commonly occurring exception to test your knowledge of checked exceptions and how you might resolve them. Start by listing scenarios where ClassNotFoundException can occur. Then, detail the steps you take to resolve this issue.

Example answer: A ClassNotFoundException can occur if the class name is incorrect, is not present in the classpath or is not in the correct package. It can also happen if a dependency is missing. In all these scenarios, the JVM cannot find the class definition and throws an exception. When resolving this issue, I check the class name, classpath and package to ensure that the JVM can find the class definition. If a dependent class is missing, I add the missing jar file to the classpath.

5. Can you list the different class loaders in Java?

Java enables the dynamic loading of classes to make the application modular, flexible and secure. Interviewers may ask this question to determine whether you know how the Java class loading mechanism works. List the different class loaders available in Java.

Example answer: The class loader is responsible for finding the class file for the requested class and loading it into memory so the JVM can execute it. The bootstrap class loader is the parent of all class loaders and loads the basic runtime classes provided by the JVM. The extension class loader inherits the bootstrap class loader and loads classes from extension directories, such as jre, lib and ext. The system class loader loads classes from the classpath. The user-defined class loader allows you to create a custom class loader to load classes from other databases or network locations.

6. Explain the concept of garbage collection in Java

Java garbage collection works by deleting unused or unreferenced objects to help free memory for other tasks. Interviewers may question you to evaluate your understanding of memory management, performance optimisation and debugging. Explain the concept of garbage collection in detail.

Example answer: When you create an object, the JVM stores it in a region of memory called the heap. The JVM checks all the objects that the application is referencing during execution. If any of these objects are no longer reachable, the JVM marks them eligible for garbage collection. The garbage collector clears the inaccessible or unreferenced objects to free up memory. After this, the garbage collector allocates a part of this memory to live and accessible objects.

Tips To Prepare For A Java Support Interview

Here are some tips to help you prepare for an interview:

Strengthen your fundamental knowledge and skills. Revise important topics such as Java basics, collections, exception handling, multithreading, input and output and networking. Read technical blogs and books and refer to the official Java documentation page to strengthen your skills.
Learn Java optimisation techniques. Revise algorithms, data structures, memory management, the Java garbage collection mechanism, caching and profiling to improve your understanding of Java optimisation techniques.
Be familiar with software development methodologies. Knowledge of software development methodologies can help you develop, test and deploy applications on time and within the specified budget. Learn about Agile, Waterfall, Scrum, Kanban and Lean methodologies and their pros and cons.
Practice debugging and troubleshooting. Ensure you are familiar with different debugging and code coverage tools. Learn about manual and automated testing techniques and hone these skills through constant practise.