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[ Solved ] Java Error when I Try to Run Minecraft via IDE


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So I'm working on a mod at the moment and prior to adding a certain element of the mod, I was able to run it just fine.

Now that I wrote up the classes and try to start Minecraft, I'm greeted with this error (The text below was ran in Debug mode):


Connected to the target VM, address: '', transport: 'socket'
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: com/mojang/authlib/exceptions/AuthenticationException
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:650)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:632)
Caused by: java.lang.ClassNotFoundException: com.mojang.authlib.exceptions.AuthenticationException
    at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:418)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:355)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:351)
    ... 7 more

Disconnected from the target VM, address: '', transport: 'socket'

Process finished with exit code 1


If anyone can tell me what's wrong and perhaps even how to fix it, that would be much appreciated!

Until then, I'll be searching up possible fixes.


EDIT: Yeah so I'm just dumb and had to update my IDE.  We good now!

Edited by TheMajorN
Solved the Issue
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