If you get a notification that Java needs to be updated do not click on the link. Go to www.java.com verify the address bar address after you get to the site. It should say https://www.java.com/en. If that is correct click on download and then run.
Three folks crashed their computers last week because they clicked on the pop-up. If you have already clicked on the link, run your anti-virus scan and anti-malware scan at once.
Never, ever update any software from a pop-up.