So, I’ve coded a Java Swing application in my Debian PC, and compiled it with IntelliJ into a JAR file. However, while it runs normally on the system it was coded on, it causes a Java Exception when running on other Windows machines. When I run it on the command line to show more details about the exception, this is the output:

-jar out.jar
Exception in thread "main" java.lang.UnsupportedClassVersionError: Main has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 52.0
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$100(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

Bare in mind that this happened even with a completely updated JRE.

Obviously, after encountering this issue, i did some research about it, and it came to me that i had to download the most recent JDK into my Windows system, as apparently Oracle stopped distributing JREs, so programs compiled in more recent versions of the JDK don’t run in computers that don’t have a JDK installed.
And this seemed to work – after installing said JDK, the program ran normally.

However, this still is an issue; not for me directly, but for those that may eventually use my software.

Let’s suppose, for example, that I make a program to help a friend of mine with something in his PC, written in Java. As he is not a developer, he doesn’t have any JDK installed on his PC, only a JRE that he may have previously installed. So, in order to make it so that he can run my program, i would have to make him install the most recent JDK into his computer, as everyone that would someday use a program that I made would have to install it as well, which doesn’t seem very practical for me.

So, in conclusion, this entire situation just made me very confused, especially as I can’t find anything in the internet that actually clearly explains what happened with the JRE – and that’s what im trying to understand better – What actually happend to the JRE? If it actually got discontinued, does that mean that everyone that wants to use a recently programmed java program have to install the JDK? Or is it just something that I am missing? Perhaps compiling in Linux instead of windows has something to do with it?

Also, I found some people saying that a fix to this issue would be to just downgrade my JDK to a version that the "most recent" JRE actually supports, but I just feel like that doesn’t quite make sense, as I would be missing on a lot of new Java features, kind of defeating the purpose of keeping the Java language updated.

So, can someone clarify all of this for me? Thanks in advance!