如何将 Stream 的元素收集到队列中？ [复制]

Question

我有以下代码：

Queue<Reward> possibleRewards = 
    Stream.of(Reward.values())
          .flatMap(reward -> IntStream.range(0, reward.getOccurencies()).mapToObj(i -> reward))
          .collect(Collectors.toList());

如您所见，我需要将Stream 的元素收集到Queue，而不是List。但是，没有 Collectors.toQueue() 方法。如何将元素收集到Queue？

Answer 1

您可以使用Collectors.toCollection()，它可以让您选择您希望生成的任何Collection 实现：

Queue<Reward> possibleRewards = 
    Stream.of(Reward.values())
          .flatMap(reward -> IntStream.range(0, reward.getOccurencies()).mapToObj(i -> reward))
          .collect(Collectors.toCollection(PriorityQueue::new)); // use whatever Queue 
                                                                 // implementation you want

Answer 2

Queue<Reward> possibleRewards = new LinkedBlockingQueue<>(); //Or whichever type of queue you would like
possibleRewards.addAll(Stream.of(Reward.values())
    .flatMap(reward -> IntStream.range(0, reward.getOccurencies()).mapToObj(i -> reward))
    .collect(Collectors.toList()));