Ask HN: Anyone for Java / JSF web apps

I regularly see new guys to want to learn programming on HN and HN shows takes them to Ruby / Python. PHP is a de-facto choice for many but they may not be too open for it considering the language purity. I also do PHP a lot though tilted towards Java. Java for me is a long standing language but (just like linux) has a host of contenders and choice it all the more confusing. Here, I would like to ask how is learning java / JSF help in web development and how to go about it in the simplest possible way. I am trying to write a Twitter clone. I know there is a ready-made example in running a Twitter-like app in ROR.