ConcurrentHashMap 与 HashMap的区别

http://www.journaldev.com/122/hashmap-vs-concurrenthashmap-%E2%80%93-example-and-exploring-iterator

http://www.java2blog.com/2014/12/concurrenthashmap-in-java.html

还有 这个 如何把HashMap 也同步起来
http://crunchify.com/hashmap-vs-concurrenthashmap-vs-synchronizedmap-how-a-hashmap-can-be-synchronized-in-java/

单独介绍ConcurrentHashMap
http://www.java2blog.com/2014/12/concurrenthashmap-in-java.html