If I remember correctly, Arduino IDE used to have “with java” and “without java” versions for download. Now java is included in all downloads.
I was trying to save some space on a small computer so I deleted java folder in arduino IDE 1.6.5 t5, arduino IDE 1.6.0 and processing IDE 3.0. The arduino IDEs are still working (but processing 3.0 stopped, no big deal). On my win 10 PC, I have java installed and in PATH variable. I suppose that arduino IDE is already calling it instead of its own included java, correct?