java.lang.NoClassDefFoundError: net/minecraft/item/ItemGroup

[MertEfe]

This happened as I was trying to add some mods to my game.
 

Description: Mod loading error has occurred

java.lang.Exception: Mod Loading has failed
    at net.minecraftforge.logging.CrashReportExtender.dumpModLoadingCrashReport(CrashReportExtender.java:69) ~[forge-1.18.1-39.0.75-universal.jar%2372!/:?] {re:classloading}
    at net.minecraftforge.client.loading.ClientModLoader.completeModLoading(ClientModLoader.java:183) ~[forge-1.18.1-39.0.75-universal.jar%2372!/:?] {re:classloading,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.lambda$new$1(Minecraft.java:553) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.Util.m_137521_(Util.java:409) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading}
    at net.minecraft.client.Minecraft.lambda$new$2(Minecraft.java:547) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.gui.screens.LoadingOverlay.m_6305_(LoadingOverlay.java:135) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:runtimedistcleaner:A}
    at net.minecraft.client.renderer.GameRenderer.m_109093_(GameRenderer.java:875) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.m_91383_(Minecraft.java:1040) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.Minecraft.m_91374_(Minecraft.java:660) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:accesstransformer:B,pl:runtimedistcleaner:A}
    at net.minecraft.client.main.Main.main(Main.java:205) ~[client-1.18.1-20211210.034407-srg.jar%2368!/:?] {re:classloading,pl:runtimedistcleaner:A}
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?] {}
    at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77) ~[?:?] {}
    at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:?] {}
    at java.lang.reflect.Method.invoke(Method.java:568) ~[?:?] {}
    at net.minecraftforge.fml.loading.targets.CommonClientLaunchHandler.lambda$launchService$0(CommonClientLaunchHandler.java:45) ~[fmlloader-1.18.1-39.0.75.jar%2323!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandlerDecorator.launch(LaunchServiceHandlerDecorator.java:37) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:53) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.LaunchServiceHandler.launch(LaunchServiceHandler.java:71) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.Launcher.run(Launcher.java:106) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.Launcher.main(Launcher.java:77) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:26) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.modlauncher.BootstrapLaunchConsumer.accept(BootstrapLaunchConsumer.java:23) [modlauncher-9.1.0.jar%235!/:?] {}
    at cpw.mods.bootstraplauncher.BootstrapLauncher.main(BootstrapLauncher.java:149) [bootstraplauncher-1.0.0.jar:?] {}

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Thread: Render thread
Stacktrace:
    at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?] {}
-- MOD sophisticatedbackpacks --
Details:
    Caused by 0: java.lang.NoClassDefFoundError: net/minecraft/item/ItemGroup
        at java.lang.Class.getDeclaredConstructors0(Native Method) ~[?:?] {}
        at java.lang.Class.privateGetDeclaredConstructors(Class.java:3373) ~[?:?] {}
        at java.lang.Class.getConstructor0(Class.java:3578) ~[?:?] {}
        at java.lang.Class.getDeclaredConstructor(Class.java:2754) ~[?:?] {}
        at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:81) ~[javafmllanguage-1.18.1-39.0.75.jar%2370!/:?] {}
        at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.0.75.jar%2369!/:?] {}
        at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) ~[?:?] {}
        at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) ~[?:?] {}
        at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {}
        at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {}

    Mod File: sophisticatedbackpacks-1.16.5-3.15.7.531.jar
    Failure message: Sophisticated Backpacks (sophisticatedbackpacks) has failed to load correctly
        java.lang.NoClassDefFoundError: net/minecraft/item/ItemGroup
    Mod Version: 1.16.5-3.15.7.531
    Mod Issue URL: https://github.com/P3pp3rF1y/SophisticatedBackpacks/issues
    Exception message: java.lang.ClassNotFoundException: net.minecraft.item.ItemGroup
Stacktrace:
    at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.1.jar:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.1.jar:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at java.lang.Class.getDeclaredConstructors0(Native Method) ~[?:?] {}
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:3373) ~[?:?] {}
    at java.lang.Class.getConstructor0(Class.java:3578) ~[?:?] {}
    at java.lang.Class.getDeclaredConstructor(Class.java:2754) ~[?:?] {}
    at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:81) ~[javafmllanguage-1.18.1-39.0.75.jar%2370!/:?] {}
    at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.0.75.jar%2369!/:?] {}
    at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) ~[?:?] {}
    at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) ~[?:?] {}
    at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {}
    at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {}

-- MOD refinedstorage --
Details:
    Caused by 0: java.lang.NoClassDefFoundError: net/minecraft/item/ItemGroup
        at java.lang.Class.getDeclaredConstructors0(Native Method) ~[?:?] {}
        at java.lang.Class.privateGetDeclaredConstructors(Class.java:3373) ~[?:?] {}
        at java.lang.Class.getConstructor0(Class.java:3578) ~[?:?] {}
        at java.lang.Class.getDeclaredConstructor(Class.java:2754) ~[?:?] {}
        at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:81) ~[javafmllanguage-1.18.1-39.0.75.jar%2370!/:?] {}
        at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.0.75.jar%2369!/:?] {}
        at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) ~[?:?] {}
        at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) ~[?:?] {}
        at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {}
        at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {}
        at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {}

    Mod File: refinedstorage-1.9.17.jar
    Failure message: Refined Storage (refinedstorage) has failed to load correctly
        java.lang.NoClassDefFoundError: net/minecraft/item/ItemGroup
    Mod Version: 1.9.17
    Mod Issue URL: https://github.com/refinedmods/refinedstorage
    Exception message: java.lang.ClassNotFoundException: net.minecraft.item.ItemGroup
Stacktrace:
    at jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[?:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.1.jar:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at cpw.mods.cl.ModuleClassLoader.loadClass(ModuleClassLoader.java:132) ~[securejarhandler-1.0.1.jar:?] {}
    at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] {}
    at java.lang.Class.getDeclaredConstructors0(Native Method) ~[?:?] {}
    at java.lang.Class.privateGetDeclaredConstructors(Class.java:3373) ~[?:?] {}
    at java.lang.Class.getConstructor0(Class.java:3578) ~[?:?] {}
    at java.lang.Class.getDeclaredConstructor(Class.java:2754) ~[?:?] {}
    at net.minecraftforge.fml.javafmlmod.FMLModContainer.constructMod(FMLModContainer.java:81) ~[javafmllanguage-1.18.1-39.0.75.jar%2370!/:?] {}
    at net.minecraftforge.fml.ModContainer.lambda$buildTransitionHandler$4(ModContainer.java:120) ~[fmlcore-1.18.1-39.0.75.jar%2369!/:?] {}
    at java.util.concurrent.CompletableFuture$AsyncRun.run(CompletableFuture.java:1804) ~[?:?] {}
    at java.util.concurrent.CompletableFuture$AsyncRun.exec(CompletableFuture.java:1796) ~[?:?] {}
    at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?] {}
    at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?] {}
    at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?] {} 
What should I do?
 

[MertEfe]

@diesieben07 I just noticed tysm 😭

[awe]

can you also help me i have this error too

[TileEntity]

Create your own thread

It is a version mismatch - Forge 1.18.1 requires 1.18.1 mods

 

So check the mod versions - if you have further issues, create a new thread