code: private List<Future<Boolean>> startTasks(ExecutorService executor, List<Callable<Boolean>> callables) {
          List<Future<Boolean>> tasks = Lists.newArrayList();
          for (Callable<Boolean> callable : callables) {
              tasks.add(executor.submit(callable));
          }
          return tasks;
      }
docs: Submit all the callables to the executor by synchronize their execution so they all start
  AFTER the have all been submitted.
  @param executor
  @param callables
  @return