I am running mujava. My mutants are not getting killed at all. They are getting generated properly but not getting killed. When i run mujava,

I am running mujava i.e. mutation testing framefork for java. I tried to run it using different versions of jdk but my mutants are not getting killed at all. They are getting generated properly but not getting killed. When i run mujava, i get following warning too in my terminal "Note: C:\mujava\result\vendingMachine\traditional_mutants\int_getCredit()\SDL_20\vendingMachine.java uses unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details.". Please help me out