Discussion of style of writing code, like always have valuable for return value, and use return for parameter check - http://www.beust.com/weblog/archives/000308.html

We should really delete the code if we need to... http://nedbatchelder.com/text/deleting-code.html

And more about programming style - http://www.codinghorror.com/blog/archives/001184.html http://www.onextrapixel.com/2011/01/20/10-principles-for-keeping-your-programming-code-clean/ 

About using Of() as factory name - http://blog.joda.org/2011/09/factory-names.html

http://blog.jooq.org/2013/08/20/10-subtle-best-practices-when-coding-java/

http://blog.activelylazy.co.uk/2014/03/10/are-comments-always-wrong/