Since upgrading to Sierra, I regularly have a pop-up window: “To use the ‘java’ command-line tool you need to install a JDK. Click ‘more info’ to visit the Java Developer Kit download website.”
But I am not a developer. I have tried turning Java on and off in Safari preferences. This pop-up continues to arise 10-20 times per day. I can get rid of it by clicking on “OK” but it is annoying.