For many Rubyists, Ruby is the first language that they learn and perhaps the only programming language that they know. Ruby provides an excellent gateway into the world of programming by allowing the newcomer to pick up its syntax rather quickly and allowing them to produce a working application within hours or even minutes using frameworks such as Rails.
Regardless of how one came to learn Ruby, I believe that programmers can benefit from learning another language that is fundamentally different, such as Java.
I'll provide a brief introduction into the world of Java from the perspective of a Rubyist. For the sake of staying focused, I'm not going to cover the difference in syntax between the two languages as this is best picked up over time, nor am I going to get into the details of more advanced Java topics such as the Java memory model or concurrency. What I do want to do is give a brief overview of the language, and why I think learning Java can benefit a Ruby programmer. Finally, I plan to cover some popular Java tools and frameworks and how they correspond to those in the Ruby world.