Help please! Issue with launching java virtual machines

Hey, so I've set up a forge 1.12.2 project with Eclipse, and no matter what, it seems to not let me run the client or server launcher for mod testing. I don't think it has to do with code, because basically the only thing I've added is the Main class, and even just starting a new project altogether, leaving it with the example mod and everything, the launcher still doesn't work. I've searched it up and tried some solutions, but none worked. I tried reinstalling the java jdk, jre and more. If you all could help, I'd appreciate it!

When I try to run the client virtual machine, the console simply reads this:

Quote

[17:18:28] [main/INFO] [GradleStart]: Extra: []

And then, an error message:

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Exception in thread "main" 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.minecraftforge.gradle.GradleForgeHacks.searchCoremods(GradleForgeHacks.java:85)
    at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:86)
    at GradleStart.main(GradleStart.java:25)