多线程Singleton单件模式
http://blog.joycode.com/ghj/archive/2009/04/13/115546.aspx
缓存
http://www.cnblogs.com/wayfarer/archive/2006/11/01/547060.html
转载于:https://www.cnblogs.com/lizh0103/archive/2009/04/27/1444672.html
