first of all sorry for my english, if i am having illegal click on my website then will the adsense close my account right at the time of illegal click or after sometime ? and how do i prevent illegal clicks ?
Google is clever, they can track IP or use other methods to check if the clicks are legit or not. If you are clicking your own ads then stop doing it immediately. While if you are being click bombed by someone then report to google asap.
If you have accidental click on any of your ads, then you can inform google about it and hope fully google will not close your account. To prevent accidental clicks, just download any ad blocker for your browser.