Java - How to use ExecutorService | Executor Framework - Part 1

This video talks about the basics of ExecutorService. It explains the importance of thread pools in java. Executor framework provides components to manage worker threads.

You can create a thread pool by calling one of the factory methods in Executors class
newFixedThreadPool - Fixed number of threads
newCachedThreadPool - Thread pool size is not limited
newSingleThreadExecutor - A Single thread in the pool
newScheduledThreadPool - Run tasks at regular intervals

In this video we talk in detail about newFixedThreadPool executor.

- As the name suggests the thread pool size is fixed.
- The corePoolSize and the maximumPoolSize is the same
- The number of threads that can be created is dictated by the maximum pool size.
- It is backed by a LinkedBlockingQueue - unbounded in size & tasks are executed in FIFO order
- If all the worker threads are busy processing tasks, then any new tasks that come in are placed in a queue. Once a worker thread is free, it grabs the tasks from the queue
- If a thread dies before shutdown because of some exception, then a new thread takes it place and starts serving new tasks.
- Fixed thread pool is a good choice when you want to limit the number of concurrent task

Executor Lifecycle:
ExecutorService can be in three states
- Running
- Shutting Down
- Terminated
Some of the important Lifecycle management methods of ExecutorService
- shutdown() - allows graceful shutdown
- shutdownNow() - abrupt shutdown
- isShutdown()
- isTerminated()
- awaitTermination(long timeout, TimeUnit unit)

For introduction to multithreading in Java, please look into my previous videos
https://youtu.be/pPVRvh6pb_I
https://youtu.be/F2TkIojBdws


#Java #Multithreading #ExecutorService #newFixedThreadPool