ArrayList<Future<Long>> futures = new ArrayList<>();
    for (int i = 0; i < nTasks; i++) {
      futures.add(
          threadPool.submit(
              new Callable<Long>() {
                @Override
                public Long call() {
                  long threadSum = 0;
                  for (int j = 0; j < getsPerTask; j++) {
                    long delta = random.nextInt(deltaRange);

    ArrayList<Future<Long>> futures = new ArrayList<>();
    for (int i = 0; i < nTasks; i++) {
      futures.add(
          threadPool.submit(
              new Callable<Long>() {
                @Override
                public Long call() {
                  long threadSum = 0;
                  for (int j = 0; j < getsPerTask; j++) {
                    long delta = random.nextInt(deltaRange);