http://blog.csdn.net/evangel_z/article/details/7624503
http://blog.163.com/wangzhengquan85@126/blog/static/36082995201182111847325/
http://niuxiaoxia870563296.iteye.com/blog/1749966
DecimalFormat
原文：http://www.cnblogs.com/zi-yao/p/6250790.html
