Server Crashing: Trouble with Forge (Concurrent Modification Exception)

[Robert Swier]

Hi everyone,

I'm encountering a puzzling error. Perhaps someone can offer some advice! I'm working with a brand-new machine running the latest update of Mac OS X (10.9.5). The latest version of Java is also installed (1.8). I installed MinecraftEdu 1.6.4, but I cannot launch the server. Upon attempting to launch the server with a new world or the tutorial world, it crashes immediately. The problem seems to be with loading the Forge mod, which is causing an Exception. 

Here is the error log:

2014-10-11 17:49:45 [INFO] [ForgeModLoader] Forge Mod Loader version 6.4.45.1 337 for Minecraft 1.6.4 loading

2014-10-11 17:49:45 [INFO] [ForgeModLoader] Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_20, running on Mac OS X:x86_64:10.9.5, installed at /Library/Java/JavaVirtualMachines/jdk1.8.0_20.jdk/Contents/Home/jre

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Java classpath at launch is minecraftedu_server.jar

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Java library path at launch is /Users/robertswier/Library/Java/Extensions:/Library/Java/Extensions:/Network/Library/Java/Extensions:/System/Library/Java/Extensions:/usr/lib/java:.

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Enabling runtime deobfuscation

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Instantiating coremod class FMLCorePlugin

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Enqueued coremod FMLCorePlugin

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Instantiating coremod class FMLForgePlugin

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Enqueued coremod FMLForgePlugin

2014-10-11 17:49:45 [FINE] [ForgeModLoader] All fundamental core mods are successfully located

2014-10-11 17:49:45 [FINE] [ForgeModLoader] Discovering coremods

2014-10-11 17:49:45 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

2014-10-11 17:49:45 [INFO] [ForgeModLoader] Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker

2014-10-11 17:49:45 [INFO] [ForgeModLoader] Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker

2014-10-11 17:49:45 [SEVERE] [ForgeModLoader] Unable to launch

java.util.ConcurrentModificationException

at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901)

at java.util.ArrayList$Itr.remove(ArrayList.java:865)

at net.minecraft.launchwrapper.Launch.launch(Launch.java:114)

at net.minecraft.launchwrapper.Launch.main(Launch.java:27)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:483)

at cpw.mods.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:48)

at cpw.mods.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:17)

I find this troubling because I haven't made any modifications at all. I have simply installed the software on a new system, and it crashes right out of the box. The only thing I can think of is that Minecraft 1.6.4 and/or the Forge mod doesn't run on the latest version of Java. But that seems really unlikely to me, so I'm hoping someone else here might have some idea what is going on. Thank you in advance for any help!

Robert Swier

Kyoto University

[Robert Swier]

Haha...well, I fixed it. I saw a note in another thread on this forum where someone said that MinecraftEdu doesn't work with Java 8. Unfortunately, Oracle does not allow older versions of Java to be installed once a newer version is already on the system. It is also not exactly easy to uninstall Java. In any case, I eventually removed Java 8 and was able to install Java 7, and now the server is running fine.

I saw later that there *is* a note in the MinecraftEdu wiki that the software needs Java 6 or 7. However, for something as critical as this, I think it should be mentioned clearly right on the download page. Or, better yet, do not distribute software that is not compatible with the latest runtime environment!

Robert Swier

[MisterA]

Hello Robert,

I am sorry to hear about your issues running the software with the latest Java. You are correct in that you are not the only one this created complications.

I am glad that you saw the wiki page with the MinecraftEdu requirements, as that is usually the first place to send people having issues with the software. Checking your setup against system requirements is always a good idea.

It is my belief that the issue is not only with Minecraft, but with Forge in general. I have the utmost confidence in the developers of MinecraftEdu that they will fix the issue as soon as it is possible. There may be something mentioned on the download page in the future, but you have to think that if it was done for java, then wouldn't you also have to post a message about any other issues of incompatibility that could happen with the countless number of possible computer setups out there in the world? Such as it does not work with old video drivers, or specifically Java 7 Update 51. I do feel that a system requirements page best suits as a solution. I will say that there could be a link to the system requirements on the download page.

Thank you for sharing your experience. Glad to hear it is all working now.

[Aleksi Postari]

Hey Robert,

There are now some Forge hotfixes available for the Java 8 issue which we will be trying out next week. Should they work, we'll definitely create a fixed 1.6.4 and 1.7.10 versions.

[Toni Paavola]

This has been fixed: http://mcedudev.tumblr.com/post/99896871164/java-8-problem-fixed

[Pcgamers Rule]

Excuse me.  I am looking for this update, but I don't have an account and there doesn't seem to be a way to register.  This type of fix out to be available to anyone who needs it to play the game.

[Matt Coia]

Pcgamers,

MinecraftEDU is no longer in production and no longer supported. Sorry. Most features are available via other methods with the standard Minecraft versions and various mods. 

Thanks!

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