多线程环境下的Hashmap和hashtable [英] Hashmap and hashtable in multithreaded environment

问题描述

我对这两个集合在多线程环境中的行为感到非常困惑.

I am really confused on how these 2 collections behave in multithreaded environment.

哈希表是同步的，这意味着不会有 2 个线程同时更新它的值，对吧?

Hash table is synchronized that means no 2 threads will be updating its value simultaneously right?

推荐答案

看ConcurrentHashMaps 用于线程安全映射.

Look at ConcurrentHashMaps for Thread safe Maps.

它们提供了 HashTable 的所有功能，性能非常接近 HashMap.

They offer all the features of HashTable with a performance very close to a HashMap.

通过不使用地图范围的锁来获得性能，该集合默认维护一个包含 16 个锁的列表，每个锁用于锁定地图的单个存储桶.您甚至可以配置存储桶的数量 :) 调整它可以根据您的数据提高性能.

Performance is gained by instead of using a map wide lock, the collection maintains a list of 16 locks by default, each of which is used to lock a single bucket of the map. You can even configure the number of buckets :) Tweaking this can help performance depending on your data.

Brian Goetz 的 Java Concurrency in Practice 我不能推荐足够多的东西http://jcip.net/

I can't recommend enough Java Concurrency in Practice by Brian Goetz http://jcip.net/

每次阅读时我都会学到一些新东西.

I still learn something new every time I read it.

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