What is the difference between ExecutorService.submit and ExecutorService.execute in this code in Java?

Question

I am learning to use ExectorService to pool threads and send out tasks. I have a simple program below

import java.util.concurrent.Execu         


        

Answer 1

As you see from the JavaDoc execute(Runnable) does not return anything.

However, submit(Callable) returns a Future object which allows a way for you to programatically cancel the running thread later as well as get the T that is returned when the Callable completes. See JavaDoc of Future for more details

Future future = executor.submit(longRunningJob);
...
//long running job is taking too long
future.cancel(true);

Moreover, if future.get() == null and doesn't throw any exception then Runnable executed successfully