I get a ConcurrentModificationException when attempting to launch Minecraft with Forge [duplicate]
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I have tried to reinstall Minecraft with Forge multiple times, but Minecraft still won't launch.
When I check "Launcher Visibility" and change it to "Hide Launcher" and re-open, I get this error log in the console:
[13:20:11] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[13:20:11] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[13:20:11] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
[13:20:11] [main/INFO] [FML]: Forge Mod Loader version 7.10.18.1180 for Minecraft 1.7.10 loading
[13:20:11] [main/INFO] [FML]: Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_20, running on Windows 7:amd64:6.1, installed at C:\Program Files\Java\jre1.8.0_20
[13:20:11] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[13:20:11] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
[13:20:11] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[13:20:11] [main/ERROR] [LaunchWrapper]: Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_20]
at java.util.ArrayList$Itr.remove(Unknown Source) ~[?:1.8.0_20]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:117) [launchwrapper-1.9.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.9.jar:?]
How can I resolve this?
Best Answer
You are not using Forge 10.13.0.1180 as shown on this line
[13:20:11] [main/INFO] [FML]: Forge Mod Loader version 7.10.18.1180 for Minecraft 1.7.10 loading
What i would do is make a copy of your saves and then completely delete the .minecraft folder from appdata.
Reinstall minecraft completely from scratch and then
Use this link to install the correct version of Forge.
It should work fine if you do this
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How to fix ConcurrentModificationException In Java | Remove an Object from ArrayList while iterating
More answers regarding i get a ConcurrentModificationException when attempting to launch Minecraft with Forge [duplicate]
Answer 2
You don't need to "downgrade" or "uninstall" Java 8 but you do need to have Java 7 on you machine - and you can run it side-by-side with 8.
The steps I took were:
- Install Java 7u76 - I went for the x64 .exe - by default it will install to
c:\Program Files\java\jre7\which should be fine, and won't upset Java 8 - but make a note of this location for step 3. - Ensure forge is up to date - at the time of writing I went for
1.7.10-Recommended 10.13.2.1230- run the updater, choosing "Forge Client" and pointing it at your Minecraft install. - Run the Minecraft Launcher, select the "Forge" profile, and select "Edit Profile", then in the "Java Settings (Advanced)" section, check the box for the executable and change the path to
c:\Program Files\java\jre7\javaw.exeand then save the profile:
- Play!
Remember though that you'll probably have to change this setting next time you update Forge as I think it seems to revert the settings back to their defaults when you run the updater.
Answer 3
Tip 1: Try down grading Java to Java 7. This is just a fail safe. Forge definitely works with Java 7
Tip 2: Make sure you have launched Minecraft without Forge before trying with Forge. Sometimes this can fix issues with Forge and Minecraft compatibility.
Tip 3: Make sure you are running the correct version of Forge.
There is no need to uninstall Minecraft and re-install.
How To Install Forge for Minecraft 1.7.10
Here is a quick tutorial video I made on installing Forge for Minecraft 1.7.10
- Download Forge for 1.7.10 from here
- Activate the installer and select "client"
- Open Minecraft launcher and select "New Profile" (bottom left)
- Name the profile something like "Forge 1.7.10" and select Forge 1.7.10 from the drop down a little further done the profile making page. Save the profile.
- Select your new profile and hit "Play"
- Enjoy playing modded Minecraft.
Answer 4
You need to get Java 7 because Java 8 is not compatible with Forge, so here's the download page.
Also, configure Java's security to medium.
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.