It's the app with an icon that looks like a blue compass. Type https://www.java.com/en/download/installed.jsp in the address bar and press ⏎ Return. It's a red button in the center of the page. This may prompt a pop-up window asking if you want to run Java on this page. The website will detect what version of Java you are running and recommend an update if needed.

Summary:
Open the Safari browser on your Mac. Go to https://www.java.com/en/download/installed.jsp in Safari. Click Verify Java Version. Click Run, to confirm.