Multithreading and Synchronization Questions and Answers for Viva

Answer-1: Multithreading is the ability of a CPU to provide multiple threads of execution concurrently, allowing multiple tasks to be processed simultaneously.

Answer-2: A process is an independent program with its own memory space, while a thread is a lightweight unit of execution within a process, sharing the same memory space.

Answer-3: Advantages include improved performance, better resource utilization, responsiveness, and the ability to perform multiple tasks concurrently.

Answer-4: A thread pool is a collection of pre-created threads that can be reused to execute tasks, improving performance by reducing the overhead of thread creation and destruction.

Answer-5: A race condition occurs when multiple threads access shared data concurrently, and the final result depends on the unpredictable order of execution.

Answer-6: Thread synchronization ensures that multiple threads do not access shared resources concurrently in a way that leads to data corruption or inconsistent results.

Answer-7: A critical section is a part of a program where shared resources are accessed and requires synchronization to ensure that only one thread at a time can access it.

Answer-8: A mutex (mutual exclusion) is a synchronization primitive that ensures that only one thread can access a critical section at a time, preventing race conditions.

Answer-9: A deadlock occurs when two or more threads are blocked forever, each waiting for the other to release resources, causing the system to halt.

Answer-10: Thread blocking occurs when a thread is prevented from proceeding with its execution, typically due to waiting for a resource or for synchronization with other threads.

Answer-11: Deadlocks can be avoided by using techniques like resource ordering, timeout mechanisms, or deadlock detection and recovery strategies.

Answer-12: A semaphore is a synchronization primitive that controls access to shared resources by using a counter to limit the number of threads that can access the resource simultaneously.

Answer-13: A mutex ensures that only one thread can access a critical section, while a semaphore allows multiple threads to access a limited number of resources concurrently.

Answer-14: A condition variable allows threads to wait for certain conditions to be met before continuing execution, enabling synchronization between threads.

Answer-15: Thread starvation occurs when a thread is perpetually denied access to the resources it needs to execute because of other threads being given priority.

Answer-16: A thread-safe data structure is one that allows multiple threads to safely access and modify it concurrently without causing data corruption or inconsistent results.

Answer-17: A blocking operation waits for a resource or condition before proceeding, while a non-blocking operation allows execution to continue without waiting for a resource.

Answer-18: A thread-local variable is a variable that is specific to a thread, ensuring that each thread has its own independent copy of the variable.

Answer-19: Deadlock prevention mechanisms involve strategies such as resource ordering or using timeouts to ensure that circular waiting conditions do not arise.

Answer-20: Common causes include circular dependencies, improper resource allocation, and holding multiple locks simultaneously.

Answer-21: Synchronization can impact performance by introducing delays due to the time spent acquiring and releasing locks, but it is necessary to ensure data integrity in concurrent environments.

Answer-22: Lock-free programming avoids using locks for synchronization, relying on atomic operations to ensure thread safety and prevent blocking.

Answer-23: The volatile keyword ensures that a variable's value is always read from memory, preventing caching or optimization, which is crucial for consistency in multithreaded programs.

Answer-24: Synchronous execution waits for one task to complete before starting another, while asynchronous execution allows multiple tasks to proceed independently without waiting for each other.

Answer-25: Atomic operations are operations that are executed completely without interruption, ensuring data consistency and preventing other threads from accessing the resource during execution.

Answer-26: A lock is a synchronization mechanism that ensures only one thread can access a critical section of code or a resource at a time, preventing race conditions.

Answer-27: A non-blocking algorithm allows a thread to proceed without waiting for other threads, improving performance by reducing idle time.

Answer-28: Synchronization can be handled using tools like locks, semaphores, condition variables, or atomic operations to ensure safe access to shared resources.

Answer-29: A livelock occurs when threads are constantly changing states in response to each other, but none of them make progress because they are continuously interacting.

Answer-30: The join method is used to wait for a thread to finish its execution before proceeding with the main thread, ensuring that the thread's work is completed before continuing.

Answer-31: A concurrent queue is a thread-safe data structure that allows multiple threads to safely enqueue and dequeue items without causing data corruption or race conditions.

Answer-32: A semaphore is used to manage access to a resource by multiple threads, controlling how many threads can access the resource simultaneously.

Answer-33: Thread-safe collections in Java are data structures like ConcurrentHashMap and CopyOnWriteArrayList that allow safe concurrent access by multiple threads.

Answer-34: A blocking queue is a thread-safe queue that allows threads to safely add and remove elements, blocking when the queue is empty or full until resources are available.

Answer-35: The wait() method causes the current thread to release the lock and wait until it is notified, while notify() wakes up a thread waiting on the condition variable.

Answer-36: An executor service in Java is a high-level API for managing and controlling the execution of threads, abstracting away manual thread management.

Answer-37: The synchronized keyword ensures that a method or block of code can only be executed by one thread at a time, preventing race conditions.

Answer-38: Lock contention occurs when multiple threads try to acquire the same lock simultaneously, leading to delays and potential performance degradation.

Answer-39: A thread-safe singleton pattern ensures that only one instance of a class is created, even when accessed by multiple threads concurrently, using synchronization techniques like double-checked locking.

Answer-40: The ReentrantLock class in Java is an implementation of the Lock interface that provides more advanced features, such as try-lock and timed lock, compared to synchronized blocks.

Answer-41: The Lock interface provides more flexibility than synchronized blocks, offering features like try-lock, timed lock, and ability to interrupt lock waiting.

Answer-42: A CountDownLatch is a synchronization aid that allows one or more threads to wait until a set of operations in other threads completes.

Answer-43: Thread safety can be ensured by using synchronization mechanisms like locks, semaphores, or atomic operations to prevent concurrent access to shared resources.

Answer-44: Immutability ensures that objects cannot be modified after creation, making them inherently thread-safe and avoiding the need for synchronization.

Answer-45: A ReadWriteLock allows multiple threads to read a shared resource concurrently, while only one thread can write to it, improving performance in read-heavy applications.

Answer-46: Thread priority allows the operating system to schedule threads with higher priority to execute before those with lower priority, influencing the order of thread execution.

Answer-47: An immutable object in Java is an object whose state cannot be changed once it is created, ensuring thread safety by preventing modifications from multiple threads.

Answer-48: Race conditions can be avoided by using synchronization mechanisms like locks, atomic operations, or thread-safe data structures.

Answer-49: Thread synchronization is crucial in web servers to ensure that multiple threads can safely access shared resources, like session data, without causing inconsistencies.

Answer-50: The ForkJoinPool is a framework for parallel processing in Java, dividing tasks into smaller subtasks and executing them concurrently, using a divide-and-conquer approach.