并发修改异常迭代

Question

I did a research about it and tried fixing this exception by changing my collections and for loops to iterators but that doesn't seem to fix it. I still get the same error.

He are the error logs from eclipse: https://imgur.com/a/uqULZsw

Here is my removeTarget function from the file BountyHunterController

public void removeTarget(Player player) {

    player.getTemporaryAttributtes().remove(TARGET_IDENTIFIER);
    player.getPackets().sendIComponentText(1296, 25, "None");

    Iterator<Player> iterator = getPlayers().iterator();
    while (iterator.hasNext()) {
        Player p = iterator.next();
        Optional<Player> targ = minigame.getTarget(p);
        if (targ.isPresent()) {
            if (targ.get().getUsername().equalsIgnoreCase(player.getUsername())) {
                p.getTemporaryAttributtes().remove(TARGET_IDENTIFIER);
                p.getPackets().sendIComponentText(1296, 25, "None");
                p.sendMessage("<col=FE1212>Your target has left, and you will be assigned another one.");
                Controler con = p.getControlerManager().getControler();
                if (con != null) {
                    if (con instanceof BountyHunterController) {
                        BountyHunterController bh = (BountyHunterController) con;
                        minigame.map.remove(type, player);
                        bh.assignTarget();
                    }
                }
            }
        }
    }
    minigame.map.remove(type, player);
    return;
}

Here is the error in line 495

Player p = iterator.next();

Note: Attempt leave, and leave are just Boolean functions checking conditions, so the error is only from this function I provided.

What am I doing wrong, and how could I solve this issue?

Answer 1

It does not matter how you handle iterators: Either behind the scenes with a for loop or yourself if you ever edit the underlying data structure while it is in use this will happen.

Ways to get around this are:

1) If you can, don't use an iterator, access the elements using a counter.

For example: for a list iterator use: for(int i=0; i<player_list.size(); i++) {... and inside the loop: player = player_list.get(i)

2) Iterate over a copy of the data structure, but of course this means copying.

3) Keep tract of your edits and do them at the end.