原始类型的易失性或同步？ [英] Volatile or synchronized for primitive type?

问题描述

在Java中，如果变量的大小小于或等于32位，则赋值是原子的，但如果大于32位则不是。

In Java, assignment is atomic if the size of the variable is less than or equal to 32 bits but is not if more than 32 bits.

什么（volatile / synchronized）在双重或长期分配的情况下使用会更有效吗？

What (volatile/synchronized) would be more efficient to use in case of double or long assignment?

赞，

  volatile double x = y;

synchronized不适用于原始参数。在这种情况下如何使用synchronized？当然我不想锁定我的类，所以不应该使用这个。

synchronized is not applicable with primitive argument. How do I use synchronized in this case? Of course I don't want to lock my class, so this should not be used.

推荐答案

如果你发现对象本身的锁定太重，那么同步就是要走的路。在Java 1.5之前，volatile可能是一个不错的选择，但是现在volatile可以通过在赋值发生的方法上强制执行指令来产生非常大的影响。创建一个单独的对象（ private final Object X_LOCK = new Object（）; ）并在设置或获取该double的值时对其进行同步。这将为您提供对锁定的精细控制，这似乎是您所需要的。

If you find locking on the object itself too heavy, then synchronized is the way to go. Prior to Java 1.5 volatile may have been a good choice, but now volatile can have a very large impact by forcing instruction ordering on the method where the assignment happens. Create a separate object (private final Object X_LOCK = new Object();) and synchronize on it when setting or getting the value of that double. This will give you a fine level of control over the locking, which it seems that you need.

在新的并发包中有更多选项，例如AtomicReference，它可能是如果你真的需要避免同步，那么它是volatile的一个很好的替代品。

In the new concurrency package there are more options, such as AtomicReference which may be a good replacement for volatile if you really need to avoid synchronization.

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