Hello,

I am trying to start my forge-modded server. I go to the point of invoking the run.bat, but I get the following error:

java.lang.IllegalArgumentException: Unsupported class file major version 66

I have Java SE Dev Kit 22.0.1 installed. Do I need to downgrade? 

Before starting a Forge dedicated server, I created a vanilla server. I did get an error when trying to connect, but I figured it was because I had mods running on the client. 

Sadly, I am pretty much "unconscious incompetent" here. 

 

Thanks for any advice. 

Edited May 4, 20241 yr by Redempsyn
Stated wrong Java version installed and added details

Hello there,  you have the wrong Java version and you need to update not downgrade. I hope this helps

Minecraft 1.20.1 requires Java 17 to work

Hi Guys,

Thanks for the replies. From what I can see I have the latest version of Java. I have Java 8 update 411 and Java SE Development Kit 22.0.1. It was late for me and I meant 22.0.1 not 11.0.1. Should I only have one installed? 

 

Thanks again!

 

Edited May 3, 20241 yr by Redempsyn
Clarity

Try and uninstall both and get Java 17

You can have multiple Java version installed

 

For the server, you have to set the path to java 17 in your startscript

For example:
 

"C:\Program Files\Java\jdk-17.0.9\bin\javaw.exe" -Xmx4G -Xms2048M -jar forgeserver.jar 
pause 

Just make sure the path is correct and keep the quotation marks

And the forgeserver jar name should match

Hi Guys,

Thanks again for the replies. Uninstalling version 22 fixed my issue. I tried starting the server using the suggestion @TileEntity gave but could not see how to invoke Forge. I then uninstalled JDK version 22 as @Xoroshio advised. I may have to stay with having only JDK 17 installed. Now I need to figure out why the startup does not like the number of mods I installed. 

you probably need to give it more RAM