Top 30 Java Multithreading Interview Questions
Multithreading is a core Java feature that allows multiple threads to run concurrently. A thread is essentially a sub-process that is typically a block of code that performs a specific function. Java Multithreading interview questions are frequently asked during software engineering interviews, such as front-end, back-end, and full-stack developer interviews. If Java is your preferred programming language, then these Java Multithreading interview questions will give you a good idea of what to expect during your interview.
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In this article, we’ll look at some common Java Multithreading interview questions and answers to help you prepare for your upcoming Java developer interview.
Here’s what we’ll discuss in this article:
- Popular Java Multithreading Interview Questions and Answers
- Sample Java Interview Questions on Multithreading
- FAQs on Java Multithreading Interview Questions
Check top Java Interview Questions to nail tech interviews.
Popular Java Multithreading Interview Questions and Answers
In this section, we’ll look at the most frequently asked Java Multithreading interview questions and answers. These questions are for freshers and experienced developers. Practice these multithreading interview questions to ace your Java technical interview.
Q1. What do you understand about a “thread” in Java programming?
A “thread is the smallest unit of processing and is a lightweight subprocess executed independently. Each thread in the program runs on a different stack frame, and multiple threads form the complete program.
Q2. What are some fundamental advantages of multithreading in Java?
The key benefits of Java multithreading include:
- Multiple threads can share single address spaces
- Threads share the same resources from the library but can execute differently
- Different threads can be made to perform various functions to yield a given result
Q3. What is the fundamental difference between a process and a thread?
A process is part of the main program, while threads are subsets of processes. Processes have different address spaces in the memory, while threads share the same address space.
Q4. What is inter-thread communication?
Communication between synchronized threads is referred to as inter-thread communication. It is a core feature that helps to avoid thread-polling in Java. A particular thread can be paused through inter-thread communication to allow another thread to enter the block.
Q5. What are some functions used to perform inter-thread communication in Java?
This is one of the most common Java Multithreading interview questions asked in tech interviews. Some common functions used to perform inter-thread communication in Java are - notify(), wait(), and notifyAll().
Q6. What do you understand about the wait() function in Java?
The wait() function, specified by the object class, is used to pause the current thread and wait until another thread calls the notify() function. Note that the wait() method needs to be called from a synchronized block to avoid an exception from occurring.
Q7. What are the different states in a thread lifecycle?
This is another Java Multithreading interview question asked at software engineering interviews. The different states in a thread life cycle include:
Q8. What do you understand by context switching?
Context switching is a feature through which the current state of a thread is saved for it to be restored and executed later. Through context switching, multiple processes can share the same CPU.
Q9. What is the function of the join() method?
The join() method causes the current thread to stop running until the thread due congregates and completes its task. It is a commonly used function that facilitates the execution of multiple threads in an organized manner.
Q10. What is the function of the sleep() method?
This is yet another popular Java Multithreading Interview Question. The sleep() method is used to pause a particular thread from executing and prioritizes another thread that needs to be executed before the current thread executes.
Q11. What do you understand about Deadlock situations in Java Multithreading?
Deadlock is a situation where each thread is waiting for resources held by other waiting threads. Due to this situation, no threads are executed, causing a pause in program execution and breaking the code at runtime.
Q12. How do you detect deadlock situations in Java?
Deadlock situations can be detected by running the executable code on cmd and subsequently collecting the thread dump. If deadlock situations are present, the cmd will throw up a message.
Q13. How can deadlock situations be avoided in Java?
This is one of the most common Java Multithreading interview questions asked in technical interviews. Deadlock situations in Java can be avoided by:
By way of avoiding nested thread locks and providing locks to only one thread at a time
By using thread join - the function helps to wait for threads to execute before other threads are executed, thereby preventing multiple threads from waiting for resources used by other threads.
Q14. Do individual threads have their respective stacks in Multithreaded programming?
Yes, individual threads have their stacks in multithreaded programming. Each thread is independent of the other and maintains its own stack in the memory.
Q15. How is thread safety achieved in multithreaded programming?
Thready safety can be achieved if multiple threads can use a particular class function without the occurrence of the race condition. In Multithreaded programming, thread safety can be achieved by:
- Use of atomic wrapper class
- Use of a volatile keyword
- Employing a lock-based mechanism
Take a look at Java OOPs Interview Questions to crack coding interviews.
Sample Java Interview Questions on Multithreading
- What do you understand about BlockingQueue?
- What do you understand by Race-condition?
- How is thread safety achieved in Java?
- What is ThreadScheduler in Java?
- What is Thread Pooling in Java?
- What are the main components to be considered while developing concurrency API?
- What are synchronized blocks, and what is their purpose?
- What is a shutdown hook?
- What are Daemon threads?
- What is Atomic action in Java?
- What are some multithreading best practices while coding in Java?
- How do you create a thread-safe Singleton?
- What would you do if threads throw exceptions within a synchronized block?
- What are the main differences between the submit() and execute() functions in Multithreading?
- What is the function of the Yield method in a Thread-class?
Know the most commonly asked Core Java Interview Questions here.
These 30 Java Multithreading interview questions will help you understand what type of multithreading interview questions to expect at Java developer interviews. Practice these questions to get ahead with your interview prep!
FAQs About Java Multithreading Interview Questions
Q1. What are Java Multithreading concepts on which interview questions are asked?
Java multithreading interview questions are based on these concepts - methods, processes, synchronization, Daemon threads, deadlocks, race conditions, thread pool, and concurrency, among others.
Q2. How do you pause a thread from running in Java?
A thread that is currently running can be paused using the sleep() method.
Q3. Is Multithreading present in other programming languages?
Multithreading is a concept that is present in many programming languages. While multithreaded languages can be made to run in a single thread, multithreading cannot be achieved in languages that don’t support the feature.
Q4. What type of Templating does Java use?
Q5. Are Java Multithreading Interview Questions asked at design interviews at FAANG companies?
Multithreading is an important concept that helps to solve present-day coding and design problems. Hence, you can expect Java Multithreading interview questions in systems design interviews at FAANG+ companies.
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