multithreading java sample

// cores can be four in my case because i have an i7 hyperthread with four physical cores.
// numThreadsToRun can be as much as you can. I usually run this code with this value set up to 10000000
// bigger the number, more time you need to finish the main task.

ExecutorService executor = Executors.newFixedThreadPool(cores * 2);

		for (int i = 1; i <= numThreadsToRun; i++) {
			if (isEmExp) {
				Future<?> future = executor.submit(Utils.showSorteredValuesReversedOrder(pathToEM));
				future.get(5, TimeUnit.SECONDS);
			}

			else if (isEm) {
				Future<?> future = executor.submit(Utils.calculateRandomEM(pathToEM));
				future.get(5, TimeUnit.SECONDS);
			} else if (isPrimitiva) {
				Future<?> future = executor.submit(Utils.calculatePrimitiva(pathToPrimitiva));
				future.get(5, TimeUnit.SECONDS);
			}

			else if (all) {
				Future<?> futureRandomEM = executor.submit(Utils.calculateRandomEM(pathToEM));
				Future<?> futurePrimitive = executor.submit(Utils.calculatePrimitiva(pathToPrimitiva));
				futureRandomEM.get(5, TimeUnit.SECONDS);
				futurePrimitive.get(5, TimeUnit.SECONDS);
			} else if (allWithExperimental) {
				Future<?> futureSortered = executor.submit(Utils.showSorteredValuesReversedOrder(pathToEM));
				Future<?> futurePrimitive = executor.submit(Utils.calculatePrimitiva(pathToPrimitiva));
				futureSortered.get(5, TimeUnit.SECONDS);
				futurePrimitive.get(5, TimeUnit.SECONDS);
			}
		}

		shutdownThreads(executor);

private static void shutdownThreads(ExecutorService executor) {
		try {
			System.out.println("attempt to shutdown executor");
			executor.shutdown();
			executor.awaitTermination(5, TimeUnit.MINUTES);
		} catch (InterruptedException e) {
			System.err.println("tasks interrupted");
			System.exit(-1);
		} finally {
			if (!executor.isTerminated()) {
				System.err.println("cancel non-finished tasks");
			}
			executor.shutdownNow();
			System.out.println("shutdown finished");
		}
	}

...
// Utils class, i only show one method...
static Runnable calculatePrimitiva(String pathToPrimitiva) {
		Runnable runnable = () -> {
			try {
				List<EMPojo> myListEMPojo = Utils.processInputFile(pathToPrimitiva);
				final Comparator<EMPojo> compTotal2017 = (p1, p2) -> Integer.compare(p1.getTotal_2017(),
						p2.getTotal_2017());
				final Comparator<EMPojo> compTotal2018 = (p1, p2) -> Integer.compare(p1.getTotal_2018(),
						p2.getTotal_2018());
				long maxSize = 7l;

				System.out.println("Primitiva 2017. ");
				myListEMPojo.stream().sorted(compTotal2017.reversed()) // sort from max to min
						.limit(maxSize).forEach(e -> System.out.println(e.toString()));

				System.out.println("Primitiva 2018. ");
				myListEMPojo.stream().sorted(compTotal2018.reversed()) // sort from max to min
						.limit(maxSize).forEach(e -> System.out.println(e.toString()));

			} catch (FileNotFoundException e1) {
				// TODO Auto-generated catch block
				e1.printStackTrace();
			}
		};
		return runnable;
	}