I rename the file to

"forge-Universal.jar" and create the bat file with"

java -Xmx12G -Xms10G -jar forge-universal.jar nogui

pause

And it comes up with this error:

D:\BudgieCraftMC1.12.2>java -Xmx12G -Xms10G -jar forge-universal.jar nogui
A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:568)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:70)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:34)
Caused by: java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class java.net.URLClassLoader (jdk.internal.loader.ClassLoaders$AppClassLoader and java.net.URLClassLoader are in module java.base of loader 'bootstrap')
        at net.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
        at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
        ... 6 more

D:\BudgieCraftMC1.12.2>pause
Press any key to continue . . .

 

Turns out I needed a new java version, I was on java 16, I needed java 8

Edited October 30, 20214 yr by JakeyCmh

Fixed, Turns out I was on the wrong java version

1.12 is no longer supported on this forum.
Please update to a modern version of Minecraft to receive support.