For security reasons Java and Adobe Flash Player were to have been unsupported by all web browsers as "obsolete" code in spring 2017 but many sites such as YouTube had millions of videos still in the conversion queue for being playable in native html5, so flash and Java got reprieves in all the major browsers such as IE/Edge, Firefox, Opera, Safari, etc. Java is still supported by many of these browsers as long as you continue to load security releases from SUN as released, otherwise you get blocked or nagged depending on the security settings of your browser. Some of these browsers now force you to turn on support either globally or on a site by site basis so check your settings if you find items blocked. But both Flash and Java's days are numbered and sooner than later no web browsers will support them under any conditions. They and their constant necessary security up-dates will be fond memories just like Apple's QuickTime player is now for windows users.
The new deadline for retirement of the Java plugins and Flash supported media is now early 2020, but most browsers will stop supporting it end of 2018, or early releases in 2019. If you still have flash objects running on your sites or use Java or flash based objects that require those players to be viewed, you can load Firefox's ESR - Extended Service Release. ESR comes in two flavors and can be used out of the box with no changes to security if you need to run full Java applets, and or use flash player objects. As with all web code, look now for updates and replacement products before you get caught in the dark.
Mozilla has listed their ESR browser releases as being serviceable until 2019. ESR is updated every 12 weeks according to Mozilla, but at work we find that ESR 52 (for XP/Vista) is updated much more frequently as is ESR 60 (Windows 7, 8, and 10). Both ESR versions seem to be in line with the current secured release version of Firefox 60.x and it's update schedule.
But the more important concept here is that Java is an object language and runs applications written in it, with or without a browser. That's why Java is deadly and a good tool for hackers to use. It can do powerful stuff. However people confuse Java with Javascript all the time. They are related but different. Javascript which was created by Netscape (aka Mozilla Firefox) in the 90's as a scripting language can only live inside an HTML page, which still has risks but is much more simple in its range of what it can do function wise. Some weather graphics are Flash or Java based, and some are stylized with Javascript, knowing what you have is necessary in order to continue using them.
Javascript while getting clunky as a language is still widely used to stylize web pages, and control page assembly and will continue to be used as such beyond the phase out of its older stronger cousin the Java plugin by Sun Micro systems. So take a look at what flavor and language your gadgets, graphs and displays on your site really use, and if it truly is a Java plugin or flash player using element you have about a year to find a replacement before most folks browsers won't play it.
More than anyone wanted to know
Brian