What are the advantages of using an ExecutorService?

Question

What is the advantage of using ExecutorService over running threads passing a Runnable into the Thread constructor?

Answer 1

ExecutorService also gives access to FutureTask which will return to the calling class the results of a background task once completed. In the case of implementing Callable

public class TaskOne implements Callable {

@Override
public String call() throws Exception {
    String message = "Task One here. . .";
    return message;
    }
}

public class TaskTwo implements Callable {

@Override
public String call() throws Exception {
    String message = "Task Two here . . . ";
    return message;
    }
}

// from the calling class

ExecutorService service = Executors.newFixedThreadPool(2);
    // set of Callable types
    Set>callables = new HashSet>();
    // add tasks to Set
    callables.add(new TaskOne());
    callables.add(new TaskTwo());
    // list of Future types stores the result of invokeAll()
    List>futures = service.invokeAll(callables);
    // iterate through the list and print results from get();
    for(Futurefuture : futures) {
        System.out.println(future.get());
    }