2009Scape Official Forums

New to 2009scape, just downloaded the launcher and followed instructions for single player and got this

Starting Singleplayer.. The Singleplayer client will launch when 2009scape is ready. Sit tight!
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: core/Server has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

Please paste your java path from the launcher settings

Java launcher settings might be removed in most recent versions, because the launcher automatically tries to use Java 11.

OP can you try simply connecting to the live server first, then close it, and run singleplayer again? This should force it to use the correct path.

C:\Program Files\Java\jre1.8.0_311\bin/java.exe
That is the requested java path from launcher settings.


As for trying to connect to the live server, it does seem that I can get to the log in screen. I don't particularly want to create an account if I don't have to though... Anyway opening and closing this doesn't make singleplayer work.

mstrzero wrote: ↑Sat Feb 03, 2024 12:39 pm C:\Program Files\Java\jre1.8.0_311\bin/java.exe
That is the requested java path from launcher settings.


As for trying to connect to the live server, it does seem that I can get to the log in screen. I don't particularly want to create an account if I don't have to though... Anyway opening and closing this doesn't make singleplayer work.

this is the wrong version of java, you should be using java 11

Ah. I see. Thank you, seems to be working fine now.

The correct java version is explicitly mentioned several times in FAQs and other places. Please check FAQs before creating bug reports and forum posts.