什么时候ConcurrentSkipListSet有用？ [英] When is a ConcurrentSkipListSet useful?

问题描述

我刚看到这个Java 6 API的数据结构，我很好奇什么时候它是一个有用的资源。我正在研究scjp考试，我看不到它覆盖在凯西·塞拉利的书，即使我看到模拟考试的问题，提及它。

I just saw this data-structure on the Java 6 API and I'm curious about when it would be an useful resource. I'm studying for the scjp exam and I don't see it covered on Kathy Sierra's book, even though I've seen mock exam questions that mention it.

推荐答案

ConcurrentSkipListSet 和 ConcurrentSkipListMap 在需要一个将由多个线程访问的排序容器时非常有用。这些基本上是用于并发代码的TreeMap和TreeSet的等价物。

ConcurrentSkipListSet and ConcurrentSkipListMap are useful when you need a sorted container that will be accessed by multiple threads. These are essentially the equivalents of TreeMap and TreeSet for concurrent code.

JDK 6的实现基于高性能动态无锁哈希表和基于列表的集合，使用比较和交换（CAS）对跳过列表执行大量操作操作。这些是无锁的，所以你不必担心在使用这些类时 synchronized （对于大多数操作）的开销。

The implementation for JDK 6 is based on High Performance Dynamic Lock-Free Hash Tables and List-Based Sets by Maged Michael at IBM, which shows that you can implement a lot of operations on skip lists atomically using compare and swap (CAS) operations. These are lock-free, so you don't have to worry about the overhead of synchronized (for most operations) when you use these classes.

目前没有基于红黑树的并发地图/在Java中设置实现。我仔细看了一遍文献，发现了一个情侣 论文显示并发RB树胜过跳过列表，但很多这些测试是通过事务内存

There's currently no Red-Black tree based concurrent Map/Set implementation in Java. I looked through the literature a bit and found a couple papers that showed concurrent RB trees outperforming skip lists, but a lot of these tests were done with transactional memory, which isn't supported in hardware on any major architectures at the moment.

我假设JDK的用户在这里使用了一个跳过列表，因为实现是很好的已知，因为使其无锁是简单和便携（使用CAS）。如果有人想要澄清，请做。我很好奇。

I'm assuming the JDK guys went with a skip list here because the implementation was well-known and because making it lock-free was simple and portable (using CAS). If anyone cares to clarify, please do. I'm curious.

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