并发编程

ConcurrentHashMap:http://blog.youkuaiyun.com/liuzhengkang/article/details/2916620

Callable和Runnable的对比：
http://www.cnblogs.com/whgw/archive/2011/09/28/2194760.html

CompletionService的用处:
http://www.cnblogs.com/Gordon-YangYiBao/archive/2012/09/16/2687309.html

CountDownLatch同步计数器的介绍：
http://www.cnblogs.com/whgw/archive/2011/09/29/2195827.html
http://www.itzhai.com/the-introduction-and-use-of-a-countdownlatch.html

ThreadLocal:
http://my.oschina.net/lichhao/blog/111362
http://my.oschina.net/u/580483/blog/113654
线程池和threadlocal同时使用的问题：
http://www.iteye.com/topic/156378