.vmoptions only work with the launchers/.exe files! The launcher will read the parameters and forward them to java.
It's not possible to set those params on already running JVM, eg running .jar directly.
JDownloader.jar, you have to manually specify those on commandline as you start the jar directly.
eg create a batch with or shortcut
javaw.exe -Xmx16g -jar JDownloader.jar
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JD-Dev & Server-Admin
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