Java Unordered() 函数

Question

在 java 8 中，当我这样做时，

类型 1

list.stream().parallel().map(/**/).unordered().filter(/**/).collect(/**/);

类型 2

list.stream().parallel().unordered().map(/**/).filter(/**/).collect(/**/);

由于两个流都是并行的，我可以理解每个操作(如过滤器、映射等)的所有对象将并行执行，但操作本身将按照定义的顺序顺序执行。

问题

1.在 Type1 中，我确实在 map() 操作之后说了 unordered() 。那么，map() 操作是否尝试处理“排序”，因为它在 unOrdered() 之前？

2.在Type2中，Ordering is not maintained across map, filter ops right?我的理解正确吗？

Answer 1

Stream 状态修改方法有 3 种:

• sequential()

  Returns an equivalent stream that is sequential. May return itself, either because the stream was already sequential, or because the underlying stream state was modified to be sequential.

• parallel()

  Returns an equivalent stream that is parallel. May return itself, either because the stream was already parallel, or because the underlying stream state was modified to be parallel.

• unordered()

  Returns an equivalent stream that is unordered. May return itself, either because the stream was already unordered, or because the underlying stream state was modified to be unordered.

如您所见，这三个都可能修改底层流状态，这意味着方法在流链中的位置无关紧要。

您的两个示例相同。那么这些将是:

list.stream().parallel().map(/**/).filter(/**/).unordered().collect(/**/);

list.stream().map(/**/).filter(/**/).unordered().parallel().collect(/**/);

list.stream().unordered().map(/**/).parallel().filter(/**/).collect(/**/);

list.stream().unordered().parallel().map(/**/).filter(/**/).collect(/**/);

您应该点击 unordered链接并阅读 javadoc 以了解有关流的排序的更多信息。