Using Eclipse, having a second screen is almost a requirement. You get surrounded by so many windows! So I use my laptop screen for all those windows, and my 24' is dedicated to the actual code.

I always work with two tabs of code, simply because a class is rarely interacting with itself so you want both sides of the pipe :).

Without Eclipse, It's a linux, terminator with 4 terminals in there and a two-paneled sublime text. I don't need my second screen for that, alt tab does the job. :)

I tried to work on Eclipse with a 9' laptop in an airport once, thought I would die before the plane take off :).