了解Java 8中的Spliterator，Collector和Stream

问题描述：

我无法理解 信息流Java 8中的 接口，特别是与 Spliterator 和 收集器 接口。我的问题是我根本无法理解 Spliterator 和收集器接口，因此 Stream 界面对我来说仍然有些模糊。

I am having trouble understanding the Stream interface in Java 8, especially where it has to do with the Spliterator and Collector interfaces. My problem is that I simply can't understand yet the Spliterator and the Collector interfaces, and as a result the Stream interface is still somewhat obscure to me.

Spliterator究竟是什么和收藏家，我该如何使用它们？如果我愿意写自己的 Spliterator 或收藏家（可能还有我自己的 Stream 在那个过程中），我应该做什么而不是做什么？

What exactly is a Spliterator and a Collector, and how can I use them? If I am willing to write my own Spliterator or Collector (and probably my own Stream in that process), what should I do and not do?

我读了一些分散在网络上的例子，但由于这里的一切都是新的并且如有变更，示例和教程仍然非常稀少。

I read some examples scattered around the web, but since everything here is stil new and subject to changes, examples and tutorials are still very sparse.

答

您几乎肯定不会处理 Spliterator 作为用户;只有在你自己编写 Collection 类型并且也打算优化它们的并行化操作时才应该这样做。

You should almost certainly never have to deal with Spliterator as a user; it should only be necessary if you're writing Collection types yourself and also intending to optimize parallelized operations on them.

对于它的价值， Spliterator 是一种以某种方式操作集合元素的方式很容易将部分收藏拆分，例如因为你是并行化的，并且希望一个线程可以在集合的一个部分上工作，一个线程可以在另一个部分上工作，等等。

For what it's worth, a Spliterator is a way of operating over the elements of a collection in a way that it's easy to split off part of the collection, e.g. because you're parallelizing and want one thread to work on one part of the collection, one thread to work on another part, etc.

你本质上永远不应该保存值类型流到一个变量。 Stream 有点像 Iterator ，因为它是一个一次性使用的对象，你几乎总是在一个流畅的链中使用，如在Javadoc示例中：

You should essentially never be saving values of type Stream to a variable, either. Stream is sort of like an Iterator, in that it's a one-time-use object that you'll almost always use in a fluent chain, as in the Javadoc example:

int sum = widgets.stream()
                  .filter(w -> w.getColor() == RED)
                  .mapToInt(w -> w.getWeight())
                  .sum();

收藏家是最普遍的，抽象的可能la map / reduce的reduce操作的版本;特别是，它需要支持并行化和完成步骤。 收集器的示例包括：

Collector is the most generalized, abstract possible version of a "reduce" operation a la map/reduce; in particular, it needs to support parallelization and finalization steps. Examples of Collectors include:

求和，例如： Collectors.reducing（0，（x，y） - > x + y）

StringBuilder追加，例如 Collector.of（StringBuilder :: new，StringBuilder :: append，StringBuilder :: append，StringBuilder :: toString）

summing, e.g. Collectors.reducing(0, (x, y) -> x + y)
StringBuilder appending, e.g. Collector.of(StringBuilder::new, StringBuilder::append, StringBuilder::append, StringBuilder::toString)

了解Java 8中的Spliterator，Collector和Stream

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