java - 做 "nothing"而 "condition"

Question

在浏览 Java 8 版本的 ForkJoinPool 的代码(与 Java 7 相比有一些有趣的变化)时，我遇到了这个结构(here):

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

我很困惑为什么你会这样写而不是这样写

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

这只是一个语义/可读性的选择，因为您可以将第一个构造读取为 do "nothing"while "conditions"？还是我缺少一些额外的好处？

Answer 1

如果你阅读了文件顶部的注释，就在类声明的正下方，有一个部分解释了这个结构的使用:

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).