摘抄自（http://tutorials.jenkov.com/java-concurrency/volatile.html）

機(jī)翻
完全不穩(wěn)定的可見(jiàn)性保證
實(shí)際上，Java volatile 的可見(jiàn)性保證超出了 volatile 變量本身。 可見(jiàn)性保證如下：

如果線程 A 寫入一個(gè) volatile 變量，而線程 B 隨后讀取了同一個(gè) volatile 變量，那么線程 A 在寫入 volatile 變量之前對(duì)線程 A 可見(jiàn)的所有變量，在線程 B 讀取 volatile 變量之后也將對(duì)線程 B 可見(jiàn)。

如果線程 A 讀取一個(gè) volatile 變量，那么在讀取 volatile 變量時(shí)線程 A 可見(jiàn)的所有變量也將從主存儲(chǔ)器中重新讀取。

原文
Full volatile Visibility Guarantee
Actually, the visibility guarantee of Java volatile goes beyond the volatile variable itself. The visibility guarantee is as follows:

If Thread A writes to a volatile variable and Thread B subsequently reads the same volatile variable, then all variables visible to Thread A before writing the volatile variable, will also be visible to Thread B after it has read the volatile variable.

If Thread A reads a volatile variable, then all all variables visible to Thread A when reading the volatile variable will also be re-read from main memory.