AtomicBoolean vs Synchronized block，有什么区别 [英] AtomicBoolean vs Synchronized block, whats the difference

问题描述

我试图了解以下两个代码块之间的区别

I am trying to understand the difference between the two following code blocks

AtomicBoolean ab = new AtomicBoolean(false);  

using the following to get and set state. .
ab.get();
ab.set(X);

vs. 

private boolean ab = false;
private final Object myboollock = new Ojbect();

public void setAB(boolean state)
{
    synchronized(myboollock)
     {
          ab = state;
     }
}

public boolean getAB()
{
 synchronized(myboollock)
 {
         return ab;
 }
}

我需要线程保护一个布尔值，仅此而已，并且有以前用过后来的方法，但是想开始用Atomic对象，(如果)它们是安全的?，

I need to thread protect a boolean, that is all, and have in the past used the later method, but would like to start to use Atomic objects, (if ) they are safe?,

推荐答案

这两个代码片段有一些细微的差别，但从外观上看是相似的:如果你调用 set 方法，随后调用 get 的其他线程将可以看到更改.

There are a few subtle differences but seen from the outside the two code snippets behave similarly: if you call the set method, the change will be visible to other threads calling get subsequently.

主要区别在于:

• 性能:根据争用的级别，您可能会使用 synchronized 或 AtomicBoolean
获得更好的性能
• 原子性:如果在某个阶段您想做的不仅仅是设置布尔值，synchronized 块将允许您以原子方式添加指令，但 AtomicBoolean 不会

• performance: depending on the level of contention, you may get better performance with synchronized or AtomicBoolean
• atomicity: if at some stage you want to do more than just setting the boolean value, a synchronized block will allow you to add instructions atomically but AtomicBoolean won't

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