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Complete begginer modder here. Illegal reflective problem.

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I was going through the codakid mod creation manual and trying to learn how this stuff works, but when i ran the configuration setting they recommended, this problem appeared. the few solutions I found on the internet made no sense to me whatsoever. Can someone explain what exactly went wrong when i tried to run minecraft.(This happened when i ran the client, to make sure i hadn't screwed up somewhere, which it seems i did). Thank you.


[2020-10-16 13:59:27] [INFO   ] Natives: C:\Users\ultim\Desktop\Project minecraft\build\natives 
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by net.minecraftforge.legacydev.MainClient (file:/C:/Users/ultim/.gradle/caches/modules-2/files-2.1/net.minecraftforge/legacydev/ to method java.lang.ClassLoader.initializePath(java.lang.String)
WARNING: Please consider reporting this to the maintainers of net.minecraftforge.legacydev.MainClient
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
[2020-10-16 13:59:27] [INFO   ] Main Class: net.minecraft.launchwrapper.Launch 
[2020-10-16 13:59:27] [INFO   ] Srg2Mcp: C:\Users\ultim\Desktop\Project minecraft\build\createSrgToMcp\output.srg 
[2020-10-16 13:59:27] [INFO   ] Extra: [] 
[2020-10-16 13:59:27] [INFO   ] Running with arguments: [--version, 1.12, --assetIndex, 1.12, --assetsDir, C:\Users\ultim\.gradle\caches\forge_gradle\assets, --accessToken, {REDACTED}, --userProperties, [], --tweakClass, net.minecraftforge.fml.common.launcher.FMLTweaker] 
Exception in thread "main" java.lang.reflect.InvocationTargetException
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:564)
    at net.minecraftforge.legacydev.Main.start(Main.java:86)
    at net.minecraftforge.legacydev.MainClient.main(MainClient.java:29)
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')
    at net.minecraft.launchwrapper.Launch.<init>(Launch.java:34)
    at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
    ... 6 more

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1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.

This is my Forum Signature, I am currently attempting to transform it into a small guide for fixing easier issues using spoiler blocks to keep things tidy.


As the most common issue I feel I should put this outside the main bulk:

The only official source for Forge is https://files.minecraftforge.net, and the only site I trust for getting mods is CurseForge.

If you use any site other than these, please take a look at the StopModReposts project and install their browser extension, I would also advise running a virus scan.


For players asking for assistance with Forge please expand the spoiler below and read the appropriate section(s) in its/their entirety.


Logs (Most issues require logs to diagnose):


Please post logs using one of the following sites (Thank you Lumber Wizard for the list):

https://gist.github.com/100MB Requires member (Free)

https://pastebin.com/: 512KB as guest, 10MB as Pro ($$$)

https://hastebin.com/: 400KB

Do NOT use sites like Mediafire, Dropbox, OneDrive, Google Drive, or a site that has a countdown before offering downloads.


What to provide:

...for Crashes and Runtime issues:

Minecraft 1.14.4 and newer:

Post debug.log

Older versions:

Please update...


...for Installer Issues:

Post your installer log, found in the same place you ran the installer

This log will be called either installer.log or named the same as the installer but with .log on the end

Note for Windows users:

Windows hides file extensions by default so the installer may appear without the .jar extension then when the .log is added the log will appear with the .jar extension


Where to get it:

Mojang Launcher: When using the Mojang launcher debug.log is found in .minecraft\logs.


Curse/Overwolf: If you are using the Curse Launcher, their configurations break Forge's log settings, fortunately there is an easier workaround than I originally thought, this works even with Curse's installation of the Minecraft launcher as long as it is not launched THROUGH Twitch:

  1. Make sure you have the correct version of Forge installed (some packs are heavily dependent on one specific build of Forge)
  2. Make a launcher profile targeting this version of Forge.
  3. Set the launcher profile's GameDir property to the pack's instance folder (not the instances folder, the folder that has the pack's name on it).
  4. Now launch the pack through that profile and follow the "Mojang Launcher" instructions above.






or alternately, 


Fallback ("No logs are generated"):

If you don't see logs generated in the usual place, provide the launcher_log.txt from .minecraft


Server Not Starting:


If your server does not start or a command window appears and immediately goes away, run the jar manually and provide the output.


Reporting Illegal/Inappropriate Adfocus Ads:


Get a screenshot of the URL bar or copy/paste the whole URL into a thread on the General Discussion board with a description of the Ad.

Lex will need the Ad ID contained in that URL to report it to Adfocus' support team.


Posting your mod as a GitHub Repo:


When you have an issue with your mod the most helpful thing you can do when asking for help is to provide your code to those helping you. The most convenient way to do this is via GitHub or another source control hub.

When setting up a GitHub Repo it might seem easy to just upload everything, however this method has the potential for mistakes that could lead to trouble later on, it is recommended to use a Git client or to get comfortable with the Git command line. The following instructions will use the Git Command Line and as such they assume you already have it installed and that you have created a repository.


  1. Open a command prompt (CMD, Powershell, Terminal, etc).
  2. Navigate to the folder you extracted Forge’s MDK to (the one that had all the licenses in).
  3. Run the following commands:
    1. git init
    2. git remote add origin [Your Repository's URL]
      • In the case of GitHub it should look like: https://GitHub.com/[Your Username]/[Repo Name].git
    3. git fetch
    4. git checkout --track origin/master
    5. git stage *
    6. git commit -m "[Your commit message]"
    7. git push
  4. Navigate to GitHub and you should now see most of the files.
    • note that it is intentional that some are not synced with GitHub and this is done with the (hidden) .gitignore file that Forge’s MDK has provided (hence the strictness on which folder git init is run from)
  5. Now you can share your GitHub link with those who you are asking for help.

[Workaround line, please ignore]


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    • 공평오피 ↘BCGAME88·COM☏ 인사오피 익선오피 청운오피 북아현오피 mty07 이방오피 응암오피 석촌오피 내수오피 pmk01 홍지오피 서산오피 적선오피 대흥오피 eft40 공항오피 양주오피 울산오피 하남오피 jvx38 평창오피 파주오피 고양오피 신영오피 yrm04 부여오피 고척오피 산림오피 용두오피 dhu55 관수오피 인사오피 냉천오피 일원오피 rth73 오산오피 익산오피 창녕오피 송정오피 fvp90 이촌오피 울산오피 구산오피 망원오피 lrc00 적선오피 창천오피 고흥오피 논산오피 wkg10 상일오피 도선오피 평택오피 송파오피 bov68 화동오피 천왕오피 파주오피 상암오피 kll86 여의도오피 염곡오피 합동오피 북가좌오피 ycj98 성내오피 율현오피 신천오피 연지오피 bgg43 노량진오피 현석오피 염리오피 용산오피 nro75 상일오피 남가좌오피 안암오피 도봉오피 iji06 장사오피 갈월오피 중구오피 세곡오피 egc22 당주오피 노고산오피 훈정오피 수하오피 dhg03 관훈오피 만리오피 신수오피 대림오피 jbq19 녹번오피 견지오피 도곡오피 대치오피 kdv76 하계오피 수서오피 세종로오피 상왕십리오피 fcu84 홍성오피 봉익오피 신사오피 상계오피 fqt59 신계오피 관수오피 중화오피 충정오피 gad51
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