Java：当使用锁时，所有可变变量是否需要是volatile？ [英] Java: Do all mutable variables need to be volatile when using locks?

问题描述

以下变量x是否需要是易失性的？

Does the following variable, x, need to be volatile?

或者在utils.concurrent锁中的操作与同步块的功能相同（确保它被写入内存，而不是存储在cpu缓存中）？

Or does the manipulation within a utils.concurrent lock perform the same function as a synchronized block (ensuring it's written to memory, and not stored in cpu cache)?

myMethod(){
  myLock.lock();
  x++;
  myLock.unlock();
}

推荐答案

如果他们在没有锁的情况下访问其他地方，则是易失的。例如，作为对大小变量的快速只读访问。锁定方法的作用与同步块相同。请参阅javadoc中锁定类。

Such variables only need to be volatile if they're accessed elsewhere without a lock. For example, as a fast read-only access to a size variable. The lock methods do serve the same purpose as a synchronized block. See the "Memory Synchronization" section in the javadoc for the Lock class.

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