Normally you would compile java using this:

javac Hello.java java Hello 

Under certain conditions you can compile from Vim by just typing :make by placing this in .vimrc

autocmd Filetype java set makeprg=java\ % 

Recently it hasn't been working though.

I've figured out that the path is the problem. How do I include it in my vimrc? I'm not sure exactly what the semantics behind that would be.