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Waylon Walker
Waylon Walker

Posted on • Originally published at waylonwalker.com

nix rescues modded minecraft night

With the latest version of minecraft it requires a very new, possibly the latest, version of java. Lately we have been getting into modded minecraft and I maintain the server for us. It's been tricky to say the least. One hurdle I recently hit involves having the wrong version of java.

I was getting this error trying to get a 1.12.2 forge server running.

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')

In researching our errors, I found this on a forum.

Pre-1.13 Forge only works with Java 8.

I don't write java, or really know how to manage different versions of java, but I have nixpkgs installed and it has a ton of odd stuff like this readily available, so searching nixpkgs landed me with this.

nix-env -iA nixpkgs.jdk8
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once I had this installed I then just changed out java for the full path to my new nixpkgs.jdk8 java and it worked.

/home/walkers/.nix-profile/bin/java -server -Xms${MIN_RAM} -Xmx${MAX_RAM} ${JAVA_PARAMETERS} -jar ${SERVER_JAR} nogui
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I don't write java or do anything other than host minecraft servers wtih it. There is probably a better way of maintaining java versions than this, but this worked for me.

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Alif-Handery

Finding the right tools for managing modded Minecraft can really enhance your gaming experience. I recently read an insightful blog about optimizing Minecraft servers that might be useful. If you're interested, check out this resource on Minecraft server manager for tips and tools to make your setup smoother!