0

So I just installed forge for 1.7.10 and 1.12.2 AND optifine for 1.14, but every time I try to launch minecraft it gives out this error:

OpenJDK 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release.
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.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
1

MinecraftForge needs java 8 and you have 9 or higher. Try installing java 8 and use it. If you don't get it work with the default launcher i'd recommend MultiMC. There you can set the java installation in preferences/java and installation of forge is much easier.

| improve this answer | |
  • thanks! it worked. – Daniel Cunha May 27 '19 at 16:35
  • FYI: Currently, MultiMC doesn't support Forge past 1.13. – Avernaism May 3 at 1:05
  • @Avernaism it actually does since 29 of March. See here – noeppi noeppi May 3 at 17:04

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.