The effect you are describing is actually the operating system's responsibility.
A jar file is never a native executable file by itself, you need the java executable on the system to run it.
So when you double click a jar file the OS needs to know that it has to execute Java and pass it this jar file. This is achieved through file association, similar to when you double click a pdf, it opens with the associated PDF Viewer program on your OS. It would be weird if PDF files hard coded in themselves the executable that you need to run it. On some dude's system Java might not be called java.exe, it could be avaj.exe, you can't know.
So the user who is double clicking the jar needs to have their OS set up to associate jar files with the Java executable installed on their system. In the past if you installed Java with Oracle's default installer, it automatically associated jar files with the installed Java, so double clicking worked at least on Windows, it might not do it anymore.
Regardless this is a setting that needs to happen on the users machine that is trying to run the file, you can't do anything about it in the jar file itself except specifying the Main-Class in your manifest file.
