q.remove(11);
    q.remove(10);
    // Now we're in the critical state: [1, 15, 13, 8, 14]
    // Removing 8 while iterating caused duplicates in iteration result.
    List<Integer> result = Lists.newArrayListWithCapacity(initial.size());
    for (Iterator<Integer> iter = q.iterator(); iter.hasNext(); ) {
      Integer value = iter.next();
      result.add(value);
      if (value == 8) {
        iter.remove();
      }

    checkNotNull(executorService);
    checkNotNull(unit);
    int ntasks = tasks.size();
    checkArgument(ntasks > 0);
    List<Future<T>> futures = Lists.newArrayListWithCapacity(ntasks);
    BlockingQueue<Future<T>> futureQueue = Queues.newLinkedBlockingQueue();
    long timeoutNanos = unit.toNanos(timeout);

    // For efficiency, especially in executors with limited