should ExecutorService be static and global
I want to use the same thread pool throughout my application. To this end, I can make ExecutorService static and global so that I can invoke ThreadUtil.executorService to get ExecutorService when I need it.
public class ThreadUtil {
public static final ExecutorService executorService = Executors.newCachedThreadPool();
}
Is it OK to instance multiple thread pools like this?
In addition, my application is a TCP server. If I don't know how big the pool should be, is it ok to simply use newCachedThreadPool?
Answer
When an instance with the same properties is to be used anywhere in your program, it is logical to declare it static and final instead of re-creating the instance each time but I would personally opt for a Singleton pattern instead of directly giving public access to the instance.
As for your second query, I don't see any problem with it. The first sentence of the documentation for newCachedThreadPool says
Creates a thread pool that creates new threads as needed
since you don't know how many threads will be created, this is the most logical choice.
Note that newCachedThreadPool will re-use old threads when they are available to increase performance.