Java - Error when removing from an ArrayList more than once. (IllegalStateException)

Question

I've been googling around for quite a bit, and can't seem to find a solution. What have I done wrong here? My problem is in the title. Here is the exception I get:

java.lang.IllegalStateException
at java.util.ArrayList$Itr.remove(Unknown Source)
at me.herp.derp.client.Config.updateItem(Config.java:24)
at me.herp.derp.client.Commands.parseCommand(Commands.java:23)
at me.herp.derp.client.ChatCommands.handleChatcommand(ChatCommands.java:29)
at net.minecraft.src.EntityClientPlayerMP.sendChatMessage(EntityClientPlayerMP.java:171)
at net.minecraft.src.GuiChat.keyTyped(GuiChat.java:104)
at net.minecraft.src.GuiScreen.handleKeyboardInput(GuiScreen.java:227)
at net.minecraft.src.GuiScreen.handleInput(GuiScreen.java:176)
at net.minecraft.client.Minecraft.runTick(Minecraft.java:1494)
at net.minecraft.client.Minecraft.runGameLoop(Minecraft.java:843)
at net.minecraft.client.Minecraft.run(Minecraft.java:768)
at java.lang.Thread.run(Unknown Source)

And here is my code:

public static void updateItem(String item, String value)
{
    if (!hasValue(item))
    {
        addItem(item, value);
        return;
    }
    for (ConfigItem c : configItems)
    {
        if (c.ITEM.equals(item))
        {
            configItems.iterator().remove();
            break;
        }
    }
    ConfigFile.saveConfig();
}

Didn't you find on google, that you should only use `iterator` to iterate over your list, if you want to modify it? — Rohit Jain, Nov 24 '12 at 08:53
@RohitJain yuo are right, post it as an answer with some explanation about it, I am sure it will help at least OP and me — Abubakkar, Nov 24 '12 at 08:55
@Abu.. and OP. See this post - http://stackoverflow.com/questions/223918/efficient-equivalent-for-removing-elements-while-iterating-the-collection. It best explains it. — Rohit Jain, Nov 24 '12 at 08:58
@RohitJain thanks but the link is not proper please edit it. — Abubakkar, Nov 24 '12 at 08:59
@Abu.. Or you can go to the wiki section of Java. There in the bottom most part, you have the link to this post. — Rohit Jain, Nov 24 '12 at 09:00

bellum · Accepted Answer · 2012-11-24T10:06:03.520

14

Your iterator wasn't initialized properly (next() was not called). I suggest to write this code like this:

Iterator<ConfigItem> it = configItems.iterator();
while(it.hasNext()){
    ConfigItem c = it.next();
    if (c.ITEM.equals(item))
    {
        it.remove();
        break;
    }
}

edited Nov 24 '12 at 10:06

answered Nov 24 '12 at 08:56

bellum

3,642
1
17
22

1

@bellum Although the code you show works, your answer isn't correct, because there is no relation between the hidden iterator used in the for loop and the iterator used in the `if` block. The `remove` method fails because it's called on an iterator not yet started, as @Evgeniy correctly points out. The same result could be obtained calling `configItems.remove(c)` inside the `if`. – remigio Nov 24 '12 at 09:52
I had complex requirement. There were nested iterator. On a condition of inner iterator have to remove object from outer iterator. the `break` statement from your answer helped me out. Thanks for sharing – Swapnil Sawant Dec 22 '15 at 13:18

score 2 · Answer 2 · answered Nov 24 '12 at 08:54

2

You can call Iterator.remove() only after Iterator.next(). Try this:

Iterator<ConfigItem> i = configItems.iterator();
while(i.hasNext()) {
    ConfigItem next = i.next();
    if (next.equals(item))
    {
        i.remove();
        break;
    }

answered Nov 24 '12 at 08:54

Evgeniy Dorofeev

133,369
30
199
275

Java - Error when removing from an ArrayList more than once. (IllegalStateException)

2 Answers2