什么是原子? [英] What is atomic?

问题描述

这是两个原子操作:

int value = 5;
Object obj = new Object();

但是当使用原语作为方法参数时，这是否被视为原子操作:<代码>public void setValue(int val, Object obj){
this.value = val;//原子?
this.obj = obj;//不是原子的?
}

But when using a primitive as a method parameter, would this be considered as an atomic operation: public void setValue(int val, Object obj){
this.value = val; // Atomic?
this.obj = obj; // Not atomic?
}

?对象引用的副本不是原子的，因为它包括读取和写入，对吗?

? The copy of the object reference is not atomic since it includes a read and a write, right?

可以说对对象引用进行原子操作的唯一方法是将其声明为 null 或为其分配一个新对象，例如:

Would it be correct to say that the only way to make an atomic operation on an object reference is to declare it null or assign a new object to it, like:

Object obj = null;

和

Object obj = new Object();

?

推荐答案

如果上面方法中的参数是一个对象的引用，那么操作不会是原子的，对吧?

If the parameter in the above method was a reference to an object, then the operation would not be atomic, right?

总的来说，这是正确的.一个好的经验法则是考虑根本没有原子性，即使是像这样的原语:

In general this is correct. A good rule of thumb is to consider there is no atomicity at all, even with primitives like:

int b,c; 
int a = ++b - c;

只有原语，但整个赋值是潜在的，不是原子的.

only primitives, but the whole assignment is potential not atomic.

如果您需要确保原子操作，您有不同的可能性:

If you need enshure atomic operations you have diferent posibilities:

• 同步块
• 不可变对象
• 特定库(java.util.concurrent.atomic)

这篇关于什么是原子?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！