Java 8 流中没有索引的原因是什么?

问题描述

我想知道 Java 8 流 (Stream<E>)，它们有以下方法:

I was wondering about the Java 8 streams (Stream<E>), they have the following methods:

• forEach(Consumer
• forEachOrdered(Consumer

反对不提供以下签名的理由是什么?

What were the arguments against not supplying the following signature?

• forEachOrdered(BiConsumer
  • 然后它将返回流中项目的索引和项目本身.

  有了这个重载，就可以在流被排序的情况下实际使用索引.

  With this overload it would be possible to actually use the index in case the stream was ordered.

  我真的很想知道反对它的论点.

  I am really curious to see what the arguments are against it.

  Edit，实际上同样适用于带有 forEachRemaining 的 Iterator 以及可能更多的类.
如果没有一个类提供这样的选项，那么我怀疑它已被考虑用于 Java 8 并被拒绝.

  Edit, the same actually holds for Iterator<E> with forEachRemaining, and possibly more classes.
If none of the classes provide such option, then I suspect it has been considered for Java 8 and denied.

  推荐答案

  索引每个元素需要顺序分配索引.这将破坏并行操作的意义，因为每个操作都必须同步才能获得其索引.

  indexing every element requires a sequential assignment of the indexes. this would defeat the point of parallel operations, since each operation would have to synchronize to get its index.

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