ConcurrentHashMap如何在内部工作？ [英] How does ConcurrentHashMap work internally?

问题描述

我正在阅读关于Java中的并发性的官方Oracle文档，我想知道 c> c> c>返回的之间的区别可能是什么？



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

code> ConcurrentHashMap 。我假设在 HashMap 上使用 synchronizeCollection（Collection< T> c）。我知道一个synchronized集合本质上只是一个装饰器为我的 HashMap 所以很明显，一个 ConcurrentHashMap 有在其内部不同的东西。

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?

编辑：我意识到源代码是公开的：
ConcurrentHashMap.java

推荐答案

我会阅读源代码ConcurrentHashMap ，因为它在细节上相当复杂。总之，它有

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）


• 使用并发锁定操作来代替线程安全。


• 有线程安全迭代器。 synchronizedCollection的迭代器不是线程安全的。


• 不公开内部锁。 synchronizeCollection。

• Multiple partitions which can be locked independently. (16 by default)
• Using concurrent Locks operations for thread safety instead of synchronized.
• Has thread safe Iterators. synchronizedCollection's iterators are not thread safe.
• Does not expose the internal locks. synchronizedCollection does.

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