Updated November 10, 2026
Java Concurrency helps developers create applications that can perform multiple tasks at the same time using different threads. In this article, we will cover the latest Java Concurrency interview questions and answers for 2026. You will learn about threads, processes, atomic operations, concurrent collections, and synchronization with simple explanations to help you prepare for technical interviews.
Java Concurrency is one of the most discussed topics in a high-level, multi-threaded programming language, which means we can develop many multi-threaded programs using Java. Multi-threaded programming contains two or more parts that run simultaneously, in which each part handles different tasks at the same time, which increases the throughput and interactivity of the program.
Computers may have several CPUs, or they may have many cores with only one CPU. Managing all these cores and building applications based on this will be the key to building an outstanding application, which is known as concurrency. It is the ability to run many processes at the same time.
Part 1 – Java concurrency Interview Questions (Basic and Advanced)
This first part covers basic interview questions and answers:
Q1. How to create a thread in Java?
Answer:
Java is a multi-threading language, which means any Java application contains at least one thread. Although many threads are running in the background, the main thread is the first Java thread for any Java application, and we can create multiple threads from it. In General, we can create a thread in two ways. The first method is by creating a Runnable interface and then creating a Thread object from it. The second method is to extend the existing Thread class.
Q2. What is the difference between Thread and Process?
Answer:
Process:
When a program is in execution, it is known as a process. It controls the blocks of any operation in a process. A process controls blocks that contain information about the process.
Thread:
A thread is a part of a process, which means a process can have many threads. Running, Ready, and Blocked are the three states of any Thread.
Q3. What are the atomic operations and methods in Java Concurrency?
Answer:
Atomic operations in concurrency perform a single unit of work without involving any other operations or processes. Atomic operations are important in multi-threaded environments like Java to avoid unpredictable data.
The most commonly used atomic variable classes in Java are AtomicLong, AtomicInteger, AtomicBoolean, and AtomicReference, which represent an int, long, boolean, and object reference, respectively, and can be updated atomically. The main methods in these classes are
- CompareAndSet()– This method returns true when it gets succeded, else returns false.
- Set()– It sets or writes the data to a memory location so that the change can also be seen by other available threads.
- Get()– It gets or accesses the value from the memory location so that the changes made by other threads are also visible.
- LazySet()– It writes the value to the memory location in a particular interval of time or may be reordered by subsequent relevant memory operations. One such use case is nullifying references for garbage collection, which can never be accessed again.
Q4. What are concurrent collection classes in Java Concurrency?
Answer:
Concurrent Collection classes support concurrent access and retrieval, and expected concurrency for making updates.
Major classes include CopyOnWriteArrayList, ConcurrentHashMap, and CopyOnWriteArraySet
Q5. What are the differences between sleep and wait methods in Java?
Answer:
The wait method is initialized in the Object class and tells the calling thread (the current thread to wait until another thread invokes it; it is also used for inter-thread communication, while the sleep method is used to pause the execution of the current thread for a particular time, and then it restarts again.
Q6. How do Traditional collections differ from Concurrent collections?
Answer:
Thread safety is the most important aspect in Java, which is ensured only by using Concurrent collections like ConcurrentMap and ConcurrentHashMap, and we cannot have thread safety while using Traditional collections like Array, LinkedList, etc. In Traditional collections, if a thread is running and another existing thread tries to add elements while it is running, we will get a RuntimeException, which can be avoided in Concurrent collections.
Q7. What is the use of CountDownLatch?
Answer:
CountDownLatch is a latch that allows one or many threads to wait until a given set of operations gets completed. Initially, a count value will be assigned to the CountDownLatch. This count gets decremented each time when it calls the countdown() method.
When a CountDownLatch object gets created, it initializes the number of threads it should wait for. There will be many threads with this condition. All such threads start the countdown by calling the countdownlatch() method. When the count decrements to zero, the task will start running.
Q8. What is a CyclicBarrier in Java Concurrency?
Answer:
CyclicBarrier is also known as a synchronizer which allows all the threads to wait for each of them until they finish their given task which means until each thread reaches a common execution point the threads that completed their task wait for other threads to complete which is also known as a barrier. They don’t continue execution without the other threads.
After a particular thread reaches an execution point, they call the await() method, which denotes that they have reached the execution or barrier point. This method rejects execution until a particular number of threads call the same method, which is also known as tripping the barrier.
Q9. What is the use of Exchanger in Java?
Answer:
Exchanger in Java is used to exchange objects containing messages between two threads. When a thread calls another thread to share messages or objects between them, it waits for the other thread to call it in return. It does not send the message until it receives a calling request from the other thread. The message is returned between the threads once both threads receive the calling request. To perform this, first, we need to call the runner thread and then the exchange() method.
Q10. What is ThreadLocal in Java?
Answer:
ThreadLocal is a Java class that gives each thread its own copy of a variable. This means one thread can change its value without affecting other threads. Developers use ThreadLocal to store and manage thread-specific data, making it useful in multithreaded applications.
Conclusion
- Java is a high-level programming language in which we can develop many multi-threaded programs and applications
- Managing cores and building applications is key to building an outstanding application, which is known as concurrency.
- Threads and concurrency are one of the most popular topics in Java Programming.
- When a program is in execution, it is known as a process, whereas a thread is a part of the process that executes based on three states: Run, Ready, and Blocked.
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This is a guide to Java concurrency interview questions. Here we discuss the introduction and basic & advanced Java concurrency interview questions, respectively. You may also have a look at the following articles to learn more –
