Java ThreadPoolExecutor Workflow

ThreadPoolExecutor is a class in Java that is used to manage thread pools, providing a convenient way to execute multiple tasks.

The workflow of ThreadPoolExecutor is as follows:

1. When a task is submitted to ThreadPoolExecutor, it is added to the task queue.
2. When the threads in the thread pool are idle, they will fetch a task from the task queue for execution.
3. If the number of threads in the thread pool has not reached the corePoolSize yet, a new thread will be created to execute the task.
4. If the number of threads in the thread pool has reached the core thread count and the task queue is full, a new thread will be created to execute the task.
5. When the number of threads in the thread pool has reached the maximum number of threads (maximumPoolSize) and the task queue is full, new tasks will be handled according to the specified rejection policy.
6. After a thread completes a task, it will retrieve the next task from the task queue to execute.
7. If there are no tasks in the task queue and the number of threads in the thread pool is greater than the core thread count, the excess threads will be destroyed.
8. If the number of threads in the thread pool is greater than the core number of threads but less than the maximum number of threads, and the threads have been idle for longer than the specified keepAliveTime, the extra threads will be destroyed.

The task queue in ThreadPoolExecutor can be a blocking queue, such as ArrayBlockingQueue or LinkedBlockingQueue, or a priority queue, such as PriorityBlockingQueue. Depending on the type of task queue used, the workflow of ThreadPoolExecutor may vary.