http://www.sw-engineering-candies.com/blog-1/comparison-of-findbugs-pmd-and-checkstyle
https://stackoverflow.com/questions/4297014/what-are-the-differences-between-pmd-and-findbugs
findbugs实践：
https://www.ibm.com/developerworks/library/j-findbug1/index.html
http://www.cnblogs.com/doit8791/archive/2012/10/22/2734730.html
阿里的Java代码规范，插件基于PMD，叫做P3C-PMD：
https://www.aliyun.com/jiaocheng/770944.html?spm=5176.100033.2.5.wcoits