现实生活中对AtomicLongFieldUpdate类的使用和说明 [英] Real life use and explanation of the AtomicLongFieldUpdate class

问题描述

有人知道对类在现实生活中的任何使用AtomicLongFieldUpdate ? 我已经阅读了说明，但是还没有完全理解它的含义. 我为什么要知道那件事?好奇心和OCPJP准备.

Is anybody aware of any real life use of the class AtomicLongFieldUpdate? I have read the description but I have not quite grasped the meaning of it. Why do I want to know that? Curiosity and for OCPJP preparation.

先谢谢了.

推荐答案

您可以考虑以下成本阶梯:

You can think of a cost ladder for the following:

• 普通long:便宜，但对多线程访问不安全
• volatile long:价格昂贵，可以安全地进行多线程访问，无法进行原子操作
• AtomicLong:最昂贵，最安全的多线程访问，可能的原子操作

• ordinary long: cheap, but unsafe for multi-threaded access
• volatile long: more expensive, safe for multi-threaded access, atomic operations not possible
• AtomicLong: most expensive, safe for multi-threaded access, atomic operations possible

(当我说不安全"或不可能"时，我的意思是没有像同步这样的外部机制".)

(When I say 'unsafe' or 'not possible' I mean 'without an external mechanism like synchronization' of course.)

在需要多线程访问但大多数操作是简单的读写的情况下，只需执行几个原子操作，就可以创建一个AtomicLongFieldUpdate静态实例，并在需要原子更新时使用它.然后，内存/运行时开销类似于简单的volatile变量，除了原子操作的数量级(或比普通AtomicLong操作的开销更高).

In the case where multi-threaded access is needed, but most operations are simple reads or writes, with only a few atomic operations needed, you can create one static instance of AtomicLongFieldUpdate and use this when atomic updates are needed. The memory/runtime overhead is then similar to a simple volatile variable, except for the atomic operations which are of the order of (or slightly more expensive than) the ordinary AtomicLong operations.

这是不错的小教程.

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