ThreadPoolExecutor Parameters Explained

Thread pool is a mechanism for managing and reusing threads, which can improve the performance and stability of multi-threaded programs.

In Java, there are two main ways to implement a thread pool: ThreadPoolExecutor and Executors.

ThreadPoolExecutor is a flexible and scalable thread pool implementation that offers more parameters and configuration options to meet various requirements. Here is a detailed explanation of the parameters in the constructor of ThreadPoolExecutor.

1. corePoolSize: the number of threads that are always kept in the thread pool, even if they are idle and not being recycled.
2. maximumPoolSize: The maximum number of threads in the thread pool, including both core threads and non-core threads.
3. If the idle time of non-core threads exceeds a certain value, they will be recycled.
4. Unit: Time unit of keepAliveTime.
5. The workQueue is a task queue used to store tasks waiting to be executed, with various implementation options such as ArrayBlockingQueue and LinkedBlockingQueue.
6. threadFactory: a factory that is used to create threads.
7. Handler: Rejection policy, new tasks will be rejected for execution when the task queue is full and the number of threads in the thread pool reaches its maximum value.

Executors is a utility class that offers various static methods for creating different types of thread pools. Here is an explanation of some common methods and their parameters in Executors:

1. Create a fixed-size thread pool with a specified number of threads, using an unbounded queue for the work tasks.
2. NewCachedThreadPool: Creates a thread pool that automatically adjusts its size according to the demand, with a corePoolSize of 0, a maximumPoolSize of Integer.MAX_VALUE, and utilizes a SynchronousQueue for the work queue.
3. newSingleThreadExecutor: Creates a thread pool with only one thread, where both the corePoolSize and maximumPoolSize are set to 1, and the workQueue uses an unbounded queue.
4. Create a fixed-sized thread pool with the option to specify the pool size, which supports the execution of tasks at scheduled times and intervals.

In summary, ThreadPoolExecutor offers more parameters and configuration options for flexible customization based on specific needs, while Executors provides common thread pool creation methods for quick and easy use. Depending on the situation, one can choose to use either one to create a thread pool.