Java流-窥视和跳过 [英] Java streams - peek and skip

问题描述

我正在为考试而学习，我对偷看感到困惑.演示代码:

I'm studying for an exam and I am confused over peek. Demo code:

Stream.of(1, 2, 3, 4, 5, 6, 7, 8, 9)
    .peek(x -> System.out.print("A" + x))
    .skip(6)
    .peek(x -> System.out.print("B" + x))
    .forEach(x -> System.out.println("C" + x));

输出:

A1A2A3A4A5A6A7B7C7
A8B8C8
A9B9C9

有人可以解释这里发生了什么吗?我所知道的是skip(6)跳过了前6个元素，而peek将在给定的时刻打印流的值.

Can someone explain what's happening here? All I know is that skip(6) skips the first 6 elements and peek will print the values of the stream at that given moment.

推荐答案

我认为该示例不必要地令人费解.

I believe that example is unnecessarily obtuse.

这实际上是完全相同的问题，但我相信输出结果会更清楚地说明正在发生的事情.它在流中每项打印一行.

Here's effectively the exact same problem but with output that I believe makes it much more clear what is going on. It prints one line per item in the stream.

Stream.of(1, 2, 3, 4, 5, 6, 7, 8, 9)
    .peek(x -> System.out.println())                //always prints
    .peek(x -> System.out.print("A" + x + " "))     //always prints
    .skip(6)                                        //"conditional"
    .forEach(x -> System.out.print("B" + x));       //sometimes prints

输出

A1 
A2 
A3 
A4 
A5 
A6 
A7 B7
A8 B8
A9 B9

整数1-6仅使其达到skip操作的高度，该操作会将其放在地板上.不允许他们达到B. skip充当屏障.

Integers 1 - 6 only make it as far as the skip operation which drops them on the floor. They are not allowed to make it as far as B. The skip acts like a barrier.

允许其余项目通过skip障碍"，并使其进入B.

The remaining items are allowed to pass through the skip "barrier" and do make it to B.

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