Error in intellij after sudden shutdown of laptop in grails/other project

I have battery problem and sometimes laptop goes off suddenly. And due to this while working i got problem in intellij while working in grails project. I did all sort of things like updating grails SDK , checking JDK and many more. The solution is so simple. 

go to intellij > file > 

then click on Invalidate and restart. and you are done. 

And if you want to delete cache without opening intellij go to 

                         home/.IntelliJIdeaXX/system 

and delete cache

here is the link to jetbrains page for cleaning system cache.

http://www.jetbrains.com/idea/help/cleaning-system-cache.html