[1.12.2] [SOLVED] ConcurrentModificationException

[Bektor]

Hi there,

 

I've got a small problem:

I got back to my old source code and wanted to finish the GUI, thought for some reason I'm running into a ConcurrentModificationException at the starting line of the for-loop.

 

--> Code is located at the beginning of initGui()
  
        this.buttonList.clear();
        this.categories = new ArrayList<>(JustAnotherEnergyAPI.getAllCategories());
        
        this.categories.sort(Comparator
                .comparingInt((LexiconCategory c) -> c.getModID().equals(Constants.MOD_ID) ? 0 : 1)
                .thenComparing(Comparator.comparing(LexiconCategory::getModID))
                .thenComparing(Comparator.comparing(LexiconCategory::getPriority))
                );
        
        for(LexiconCategory category : this.categories) { // TODO: limit number of categories per page
            this.categories.add(category);
            this.buttonList.add(new GuiButtonCategory(category.getPriority(), this.left + 20, this.top + 20, this.guiWidth, 30, category.getUnlocalisedName()));
        }

 

  Quote

[main/FATAL] [net.minecraft.client.Minecraft]: Unreported exception thrown!
java.util.ConcurrentModificationException: null
	at java.util.ArrayList$Itr.checkForComodification(ArrayList.java:901) ~[?:1.8.0_144]
	at java.util.ArrayList$Itr.next(ArrayList.java:851) ~[?:1.8.0_144]
	at minecraftplaye.justanotherenergy.client.gui.GuiModBook.initGui(GuiModBook.java:74) ~[GuiModBook.class:?]
	at net.minecraft.client.gui.GuiScreen.setWorldAndResolution(GuiScreen.java:543) ~[GuiScreen.class:?]
	at net.minecraft.client.Minecraft.displayGuiScreen(Minecraft.java:1096) ~[Minecraft.class:?]
	at net.minecraftforge.fml.client.FMLClientHandler.showGuiScreen(FMLClientHandler.java:534) ~[FMLClientHandler.class:?]
	at net.minecraftforge.fml.common.FMLCommonHandler.showGuiScreen(FMLCommonHandler.java:321) ~[FMLCommonHandler.class:?]
	at net.minecraftforge.fml.common.network.internal.FMLNetworkHandler.openGui(FMLNetworkHandler.java:112) ~[FMLNetworkHandler.class:?]
	at net.minecraft.entity.player.EntityPlayer.openGui(EntityPlayer.java:2809) ~[EntityPlayer.class:?]
	at minecraftplaye.justanotherenergy.common.items.ItemLexicon.onItemRightClick(ItemLexicon.java:41) ~[ItemLexicon.class:?]
	at net.minecraft.item.ItemStack.useItemRightClick(ItemStack.java:234) ~[ItemStack.class:?]
	at net.minecraft.client.multiplayer.PlayerControllerMP.processRightClick(PlayerControllerMP.java:543) ~[PlayerControllerMP.class:?]
	at net.minecraft.client.Minecraft.rightClickMouse(Minecraft.java:1710) ~[Minecraft.class:?]
	at net.minecraft.client.Minecraft.processKeyBinds(Minecraft.java:2379) ~[Minecraft.class:?]
	at net.minecraft.client.Minecraft.runTickKeyboard(Minecraft.java:2145) ~[Minecraft.class:?]
	at net.minecraft.client.Minecraft.runTick(Minecraft.java:1933) ~[Minecraft.class:?]
	at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:1186) ~[Minecraft.class:?]
	at net.minecraft.client.Minecraft.run(Minecraft.java:441) [Minecraft.class:?]
	at net.minecraft.client.main.Main.main(Main.java:118) [Main.class:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_144]
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135) [launchwrapper-1.12.jar:?]
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.12.jar:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_144]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_144]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_144]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_144]
	at net.minecraftforge.gradle.GradleStartCommon.launch(GradleStartCommon.java:97) [start/:?]
	at GradleStart.main(GradleStart.java:25) [start/:?]

 

Expand  

Thx in advance.

Bektor

Edited September 11, 2018 by Bektor

[jabelar]

This is a Java thing about modifying certain types of collections (like List) while iterating through it. You need to use a proper iterator and safe methods instead of a for loop. See discussion here: https://stackoverflow.com/questions/15384486/java-concurrent-modification-exception-error

[Bektor]

  On 9/11/2018 at 4:29 PM, jabelar said:

This is a Java thing about modifying certain types of collections (like List) while iterating through it. You need to use a proper iterator and safe methods instead of a for loop. See discussion here: https://stackoverflow.com/questions/15384486/java-concurrent-modification-exception-error

Expand  

Ok, thx.

[Draco18s]

In detail:

  On 9/11/2018 at 4:25 PM, Bektor said:

        for(LexiconCategory category : this.categories) { // TODO: limit number of categories per page
            this.categories.add(category);

Expand  

What is this even intended to mean, "for each category in list, add the category to the list?" What?

[KlingonBoi]

I just modded the game and it gave me this error... why? 

[DaemonUmbra]

Please don't Necro old threads, if you have an issue make your own.