Java concurrency is a feature of Java that allows developers or programmers to run multiple programmes in parallel and ensure high performance. During a software developer or programmer interview, hiring managers may ask technical and advanced questions to evaluate your knowledge related to java concurrency. Reviewing such questions and learning how to answer them can help you increase your chances of getting hired. In this article, we discuss a list of java concurrency interview questions along with their sample answers and provide a few tips to help you prepare for the interview.
Java concurrency interview questions with sample answers
Here are some Java concurrency interview questions with their sample answers that you can use as an inspiration to create your own responses:
- What is the difference between a thread and a process?
Interviewers may ask this question to analyse your basic computer science knowledge. Threads and processes are the independent sequence of execution and may relate to each other. While answering this question, focus on responding in a very clear, concise and factual way.
Example: ‘A thread is basically a lightweight unit of execution within the process. On the other hand, a process is a heavyweight unit of execution having its own memory of space and system resources. Both the threads and processes are similar to each other because they are independent sequences of execution. In simple words, a thread is a segment of a process and a process is a program under execution. As a lightweight process, a thread takes fewer resources while a process requires more resources to execute.
- What do you know about race conditions in multi-threading?
A race condition in multi-threading is a situation when multiple threads access and modify the same shared resource. Interviewers may ask this question to know if you are aware of race conditions and their characteristics. While answering this question, it can be helpful to keep your answers informative and to the point. You may also try elaborating on race conditions with the help of examples.
Example: ‘Race conditions in multi-threading are concurrency bugs which are caused due to the parallel execution of the programme using multiple threads at the same time. The risk of race conditions is higher in Java because it is a multi-threading programming language. To avoid race conditions from happening, it is important to find their root cause. A simple example to make it more simple can be a bank account scenario where two different threads are trying to withdraw money from the same account simultaneously.’
- What is synchronisation in Java and how can you achieve it?
Synchronisation in Java can help in controlling the access of multiple threads to shared resources. This question can help interviewers assess your knowledge about this topic. While answering this question, consider highlighting your experience with synchronisation in Java and its applications. Make sure you use a professional tone while responding to the interviewer.
Example: ‘Synchronisation is as a process or mechanism in Java which ensures that only one thread is responsible for executing critical sections of code at a time. We can achieve synchronisation in Java with the help of a synchronised keyword by applying it to a block of code. We can also achieve it using the java.util.concurrent.locks package. This results in providing more advanced synchronisation mechanisms.’
- What do you know about inter-thread communication?
The concept of inter-thread communication helps synchronised threads communicate with each other. While answering this question, explain the meaning of inter-thread communication in Java and how it can be useful. During your interview, you can expect questions like this that prove your knowledge and skills as a software developer.
Example: ‘Inter-thread communication in Java refers to the mechanism using which threads can synchronise and communicate with each other. This process is useful for pausing a running thread to allow another thread to enter the same critical section. There are various methods using which we can achieve inter-thread communication in Java. Some of them are wait() and notify() methods, join() method, synchronised keyword, volatile keyword and java.util.concurrent package.’
- Please describe multithreading and its uses.
This question can help interviewers test your basic knowledge and understanding of multithreading and its benefits. Describe your answer in an informative way and explain how you use multithreading to improve the performance of Java applications. Consider highlighting examples from your previous work when you used multithreading.
Example: ‘Multi thread in Java gets created using the thread class, companion interface, its message and runnable. We can understand multithreading in Java by the capacity and ability of a Java virtual machine (JVM) to allow the execution of multiple threads concurrently. There are various uses of multithreading in Java concurrency such as improving the performance of an application. It makes Java applications more responsive. In addition, it is also helpful in utilising multiple CPU cores, reducing the idle time and performing multiple tasks at the same time.’
Tips to prepare for a Java concurrency interview
During an interview, hiring managers may ask different types of questions to assess your fluency with Java concurrency. While answering such questions, focus on providing factual and reasonable answers. You may highlight how your previous experience can help you in solving issues and finding the best suitable solutions. Here are some effective tips that may help you prepare for a Java concurrency interview:
Understand the basics of Java concurrency and multithreading
Concurrency in Java is the capability of a Java virtual machine to run multiple threads concurrently. It can be helpful to understand the basics of concurrency and multithreading in Java. Interviewers may ask you different questions related to concurrency and threading including their characteristics or their use in Java applications. You can pursue relevant courses to enhance your concurrency and multithreading skills. It can also differentiate you from other candidates during the interview. Here are a few online certifications that you can pursue:
- Parallel programming in Java
- Concurrent programming in Java
- Distributed programming in Java
Learn more about java.util.concurrent package
Many Java developers use this package for building concurrent Java applications. Having a deep knowledge of this package can be helpful in applying for a Java developer job role. Interviewees may ask different questions related to the components or utilities of this package. The java.util.concurrent package also provides various classes that support the scheduling of tasks and thread-safe queuing. Preparing for your Java concurrency interview may require familiarising yourself with this package and learning more about it.
Practise mock interviews
Practising mock interviews before appearing in the real interview can be a great way to prepare your answers in advance. It can also teach you the right way to deliver your responses. You can practise mock interviews and find the areas where you require improvement. Getting feedback on your mock interview performance can help you identify your mistakes. Find a partner who can take your mock interviews and prepare concepts and techniques strictly related to Java concurrency.
Improve your technical skills
Study the fundamentals of Java and learn the major terms associated with it. During an interview, hiring managers may ask you about atomic operations, synchronisation, threads, java.util.concurrent package, thread safety or different types of locks. Study the basic concept of these terms, their benefits and methods to use them. You can try practising and solving problems related to concurrency and multithreading. This may allow you to improve your technical skills and gain a deep understanding of Java concurrency.
Research the job description and the company
Researching the job description you are applying for can help in getting important insights about the position and the company. A job description may contain the necessary skills and qualifications required for the role. Consider researching the company to get an understanding of the products or services they are offering. Explore the technology they are working with and the types of projects they handle. This may give you an idea of what problems they may face during a project related to concurrency. During an interview, you can explain how your experience and knowledge can help the company in fixing those concurrency-related issues.
