I have a brand new Version of Ubuntu installed today (Ubuntu 20.04 LTS). I tried to make a forge 1.12.2 server. I tried running "forge-1.12.2-14.23.5.2854.jar" in the console with "sudo java -jar forge-1.12.2-14.23.5.2854.jar"  and "java -jar forge-1.12.2-14.23.5.2854.jar" but everytime it just prints out:

 

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:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    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

 

I don't really know what to do. Ever thread I read is successful and great and all but nothing works. Its so annoying... I tried to install several versions of Java, installing another Server. Nothing,nothing works. I am so annoyed and don't know what to do.

 

I did "java -version":

 

openjdk version "14.0.1" 2020-04-14
OpenJDK Runtime Environment (build 14.0.1+7-Ubuntu-1ubuntu1)
OpenJDK 64-Bit Server VM (build 14.0.1+7-Ubuntu-1ubuntu1, mixed mode, sharing)

 

Edited June 23, 20205 yr by rarbin
Java version

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