Skip to main content

Concurrency

CompletableFuture Event Loop​

  • To run asynchronous tasks on a single thread or a default thread pool

Mechanisms in Java​

  • java.util.concurrent utilities (ExecutorService, ConcurrentHashMap)
  • Asynchronous APIs like CompletableFuture or Future
  • Synchronization tools (synchronized, CountDownLatch, ReentrantLock)

Solutions to Data Consistency​

  1. Transaction Management
    : Use database transactions to ensure that a group of database operations either all succeed or all fail and are rolled back.
  2. Lock Mechanism
    : Use locks to prevent multiple threads from accessing shared resources simultaneously.
  3. Version Control
    : Through optimistic locking, record version information of data during updates to prevent simultaneous modifications to the same data, thus ensuring data consistency.

Question​

1. What is the difference between a process and a thread?​

  • Process: A process is a program in execution, separate memory space.
  • Thread: A lightweight unit of execution within a process, sharing the process's memory and resources.

2. What is the difference between process switching and thread switching?​

  • Process switching:
    1. Switching the CPU between different processes.
    2. Require saving and loading the entire process state (register, memory mapping) which is resource-intensive.
    3. Slower.
  • Thread switching:
    1. Switching between threads within the same process.
    2. Threads share the same memory space, only the thread's stack and registers need to be saved and loaded.
    3. Faster.

3. What is the difference between parallelism and concurrency?​

  • Parallelism: Perform multiple tasks simultaneously on multiple CPU cores.
  • Concurrency: Perform multiple tasks simultaneously on a single CPU core.

4. What is a daemon thread?​

  • A daemon thread is a low-priority thread that runs in the background to provide services (e.g., garbage collection).