public void run() {
              currentFuture.get().addListener(listener, executor);
            }
          });
    }
    assertEquals(allTasks.size() + 1, barrier.getParties()); // sanity check
    for (int i = 0; i < 1000; i++) {
      Collections.shuffle(allTasks);
      final AbstractFuture<String> future = new AbstractFuture<String>() {};