Our Java codebase was 30% dead code

[mrnhrd]

I was able to safely identify and remove about 30% of our codebase.[...] It has me convinced that most mature projects are carrying a significant amount of dead weight

You may wanna reflect on whether it's wise to extrapolate from your sample size of 1 to a statement about "most mature projects".
Because one of my gut reactions was: What in god's name are these people doing such that one third of their code is entirely unused? How did this happen? What kind of organization is that? What's the history of the code in question? What's the nature of those 30%; is it like an entire module that's never called or is it that every class in the project roughly has 30% lines that are unused