Many computer users got this problem. It is really annoying to meet this kind of pop-ups. Actually, it is a little big topic. Cases are different when getting Java Update Popup. It may come from a real Java program. But if you keep getting popup, there may be something in your computer. Below are the details.
Java Update Popup from website

Just like the screenshot above, if you keep getting redirected to this kind of java update domain, you may infect with adware or PUP. The adware or PUP may have already installed on your control panel and added to your browser extension. It changes our browser settings so this kind of popup keeps showing up. Please watch a video about this kind of popup.