ConcurrentHashMap 内部如何工作? [英] How does ConcurrentHashMap work internally?

问题描述

我正在阅读有关 Java 并发的 Oracle 官方文档，我想知道

I was reading the official Oracle documentation about Concurrency in Java and I was wondering what could be the difference between a Collection returned by

public static <T> Collection<T> synchronizedCollection(Collection<T> c);

并使用例如

ConcurrentHashMap.我假设我在 HashMap 上使用了 synchronizedCollection(Collection c).我知道通常同步集合本质上只是我的 HashMap 的装饰器，所以很明显 ConcurrentHashMap 在其内部有一些不同的东西.你有关于这些实施细节的一些信息吗?

ConcurrentHashMap. I'm assuming that I use synchronizedCollection(Collection<T> c) on a HashMap. I know that in general a synchronized collection is essentially just a decorator for my HashMap so it is obvious that a ConcurrentHashMap has something different in its internals. Do you have some information about those implementation details?

我意识到源代码是公开的:ConcurrentHashMap.java

推荐答案

我会阅读 ConcurrentHashMap 的来源 因为它在细节上相当复杂.总之就是

I would read the source of ConcurrentHashMap as it is rather complicated in the detail. In short it has

• 可以独立锁定的多个分区.(默认为 16)
• 使用并发锁操作来确保线程安全而不是同步.
• 具有线程安全迭代器.synchronizedCollection 的迭代器不是线程安全的.
• 不暴露内部锁.synchronizedCollection 确实如此.

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