Java同步参考 [英] Java synchronized references

问题描述

我有A类和B类.

public class A() { 
    private static List<int> list = new ArrayList<int>(); 
    public static List<int> getList() {
        return list;
    }
}

public class B() { 
    public void foo() {
        synchronized(A.getList()) {
            // DO Stuff
        }
    }
}

在我同步的B类中.这是否在A的列表上或B在对A的列表的引用上同步.我认为是后者，但可以使用一些帮助.

In class B where I synchronize. Does this synchronize on A's list, or on B's reference to A's list. I think it is the latter but could use some help.

如果是这样，那么我该如何完成与实际可行的功能类似的事情?

If so then how do I accomplish a similar thing to this that will actually work?

谢谢！

推荐答案

OP随后发表了以下评论:

The OP followed up with this comment:

我所看到的行为很奇怪，就是如果我从A内锁定，我实际上可以同时在B中锁定它.这在很大程度上意味着同步无效.这就是为什么我认为锁定参考无法正常工作的原因.

What's weird is the behavior that I am seeing is that if I lock from within A I can actually lock it at the same time in B. Which pretty much means the synchronized has no effect. Which is why I surmised that maybe locking a reference won't work.

问题代码无法实现.

但是如果A中有一个setList方法更新了list变量，则可能会发生这种情况.然后，您可能会遇到两个线程锁定在不同对象上的情况.

But it could happen if there was a setList method in A that updated the list variable. You could then end up in a situation where the two threads were locking on different objects.

另一种可能性是您实际上只有一个线程对同一对象进行两次锁定.这是正常现象. Java基本互斥体是可重入的；也就是说，它们仅阻止两个不同线程同时保留相同的互斥量.

Another possibility is that you actually only have one thread that is taking a lock on the same object twice. That's normal behavior. Java primitive mutexes are reentrant; i.e. they only prevent two different threads from holding the same mutex at the same time.

这篇关于Java同步参考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！