Java8中Iterator和Spliterator之间的区别

问题描述：

我在研究 Parallelism 时发现了 Spliterator 的主要优势。

I came to know while studying that Parallelism is a main advantage of Spliterator.

这可能是一个基本问题，但任何人都可以向我解释 Iterator 和 Spliterator $ c之间的主要区别$ c>并给出一些例子？

This may be a basic question but can anyone explain me the main differences between Iterator and Spliterator and give some examples?

答

这些名字对我来说几乎是不言自明的。 Spliterator == Splittable Iterator ：它可以拆分一些源，也可以迭代它。它有一些像 Iterator 一样的功能，但是它可以将拆分分成多个部分，这就是 trySplit 适用于。并行处理需要拆分。

The names are pretty much self-explanatory, to me. Spliterator == Splittable Iterator : it can split some source and it can iterate it too. It's sort of has the same functionality like an Iterator, but with the extra thing that it can potentially split into multiple pieces, this is what trySplit is for. Splitting is needed for parallel processing.

迭代器总是一个未知的大小，你只能通过 hasNext /下一; Spliterator 可以提供大小（从而在内部改进其他操作）;要么通过 getExactSizeIfKnown ，要么通过估计大小。

An Iterator has always an unknown size, you can traverse elements only via hasNext/next; a Spliterator can provide the size (thus improving other operations too internally); either an exact one via getExactSizeIfKnown or a approximate via estimateSize.

另一方面， tryAdvance 是 hasNext / next 来自 Iterator ，但这是一种方法，更容易推理IMO。与此相关的是 forEachRemaining ，它在默认实现中委托给 tryAdvance ，但它不一定像这样。（例如，参见 ArrayList ）

On the other hand, tryAdvance is what hasNext/next is from an Iterator, but it's a single method, much easier to reason about IMO. Related to this is forEachRemaining which in the default implementation delegates to tryAdvance, but it does not have to be like this always. (see ArrayList for example)

Spliterator也是一个更聪明的迭代器，通过它的内部属性如 DISTINCT 或 SORTED 等（在实现自己的 Spliterator时需要正确提供 code>）。这些标志在内部用于禁用不必要的操作，也称为优化，例如：例如：

A Spliterator is also a "smarter" Iterator, via it's internal properties like DISTINCT or SORTED, etc (which you need to provide correctly when implementing your own Spliterator). These flags are used internally to disable unnecessary operations, also called optimizations, like this one for example:

 someStream().map(x -> y).count();

因为在流的情况下大小不会改变，所以地图可以完全跳过，因为我们所做的只是计算。

Because size does not change in case of the stream, the map can be skipped entirely, since all we do is counting.

如果您需要，可以在Iterator周围创建一个Spliterator，通过：

You can create a Spliterator around an Iterator if you would need to, via:

Spliterators.spliteratorUnknownSize(yourIterator, properties)

Java8中Iterator和Spliterator之间的区别

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