long addRemove(int reps) throws ExecutionException, InterruptedException {
    return doMultithreadedLoop(
        new Callable<Long>() {
          @Override
          public Long call() {
            return runAddRemoveSingleThread(reps);
          }
        });
  }

  private long doMultithreadedLoop(Callable<Long> task)
      throws InterruptedException, ExecutionException {