import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;

public class Main {

    public static void main(String[] args) throws ExecutionException, InterruptedException {

        // ***************** manual
        Future<Integer> f = new FutureTask<>(() -> {
            System.out.println("toto");
            return 1;
        });

        showState(f);
        ((FutureTask<Integer>) f).run();


        // ***************** with pool
        int nbProcs = Runtime.getRuntime().availableProcessors();
        ExecutorService exec = Executors.newFixedThreadPool(nbProcs);
        Future f2 = exec.submit(() -> {
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                System.out.println("failed to sleep");
            }
        });

        showState(f2);

        System.out.println("Hello World!");
    }

    /**
     * show state of future callback
     * @param f
     * @throws InterruptedException
     * @throws ExecutionException
     */
    private static void showState(Future<Integer> f)
        throws InterruptedException, ExecutionException {
        System.out.println("is cancel : " + f.isCancelled());
        System.out.println("is done : " + f.isDone());
        System.out.println(f.get());
    }
}