When should I use a CompletionService over an ExecutorService?

Question

I just found CompletionService in this blog post. However, this does\'t really showcases the advantages of CompletionService over a standard ExecutorService. The same code c

Answer 1

Basically you use a CompletionService if you want to execute multiple tasks in parallel and then work with them in their completion order. So, if I execute 5 jobs, the CompletionService will give me the first one that that finishes. The example where there is only a single task confers no extra value over an Executor apart from the ability to submit a Callable.