How to fix Hadoop WARNING: An illegal reflective access operation has occurred error on Ubuntu

There is nothing you can do about these warnings, this is related to jigsaw project and strong(er) encapsulation.

Basically there is some class called sun.security.krb5.Config that is part of some "module" called java.security.jgss. This module "defines" what it exports (what others can use out of it) and to whom. This also means in plain english that this is not for the public usage - don't touch it; well hadoop did, it's part of their effort to fix this. You can report this or try to upgrade hadoop, may be this is already fixed.

this problem is due to latest java upgrades.please configure it with java 8.its working swiftly.