How to find out number of files currently open by Java application?

Question

Suppose a lot of what your application does deals with reading contents of files. It goes without saying that files that are opened then closed and life is good unless ... n

Answer 1

Sorry for necroposting, but guys, you're ignoring -K option of lsof cause java have threads, each of them have their own FD that are living in /proc/$PID/tasks/fd/

and there is A HUGE difference:

root@xxx:/root# lsof -p 13553 | wc -l
612
root@xxx:/root# lsof -p 13553 -K | wc -l
112108