做什么都没有而“条件”则 [英] Do "nothing" while "condition"

问题描述

在浏览ForkJoinPool的Java 8版本的代码时（我从Java 7中进行了一些有趣的更改）我遇到了这个结构（这里）：

While browsing the code for the Java 8 version of ForkJoinPool(which has a few interesting changes from Java 7) I ran across this construct (here):

do {} while (!blocker.isReleasable() &&
             !blocker.block());

我为什么要像这样写它而不仅仅是

I'm struggling with why you would write it like this instead of just

while (!blocker.isReleasable() &&
       !blocker.block());

它只是一个语义/可读性选择，因为你可以读取第一个结构在条件时做没事？或者我还缺少一些额外的好处吗？

Is it just a semantics/readability choice, since you could read the first construct as do "nothing" while "conditions"? Or is there some additional benefit I'm missing?

推荐答案

如果你阅读文件顶部的评论，就在下面类声明，有一节解释了这个结构的用法：

If you read the comments at top of the file, just below the class declaration, there is a section which explains the use of this construct:

Style notes

===========

[...]

There are several occurrences of the unusual "do {} while
(!cas...)"  which is the simplest way to force an update of a
CAS'ed variable. There are also other coding oddities (including
several unnecessary-looking hoisted null checks) that help
some methods perform reasonably even when interpreted (not
compiled).

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