LibGDX Bomberman bomb arraylist iterator error

Question

Here is the code of bomb:

private int x, y;
private Texture bTexture;
private boolean bomb_explode;

private Timer timer;
private TimerTask task;
private int timeLeft = 0;

private TileMap map;
public static List<Bomb> bombs = new ArrayList<Bomb>();

public Bomb(TileMap map, int x, int y) {
    this.map = map;
    this.x = x;
    this.y = y;
    bTexture = new Texture("bomb.png");
    bomb_explode = false;
    bombs.add(this);
    createTimer();
}

public void render(SpriteBatch batch, float delta) {
    batch.draw(bTexture, x * Settings.SCALED_TILE_SIZE, y * Settings.SCALED_TILE_SIZE,
        Settings.SCALED_TILE_SIZE, Settings.SCALED_TILE_SIZE);
    if(timeLeft > 1f) {
        bomb_explode = true;
    }
    if(bomb_explode) {
        for(int i = 0; i <= 1; i++) {
            if(x + i <= map.getWidth()) {
                batch.draw(new Texture("flame.png"), 
                    ((x + i) * Settings.SCALED_TILE_SIZE), y * Settings.SCALED_TILE_SIZE, 
                     Settings.SCALED_TILE_SIZE, Settings.SCALED_TILE_SIZE);
            }
            if(y + i <= map.getHeight()) {
                batch.draw(new Texture("flame.png"), x * Settings.SCALED_TILE_SIZE, 
                   ((y + i) * Settings.SCALED_TILE_SIZE), Settings.SCALED_TILE_SIZE, 
                   Settings.SCALED_TILE_SIZE);
            }
            if(x - i >= 0) {
                batch.draw(new Texture("flame.png"), 
                    ((x - i) * Settings.SCALED_TILE_SIZE), y * Settings.SCALED_TILE_SIZE, 
                    Settings.SCALED_TILE_SIZE, Settings.SCALED_TILE_SIZE);
            }
            if(y - i >= 0) {
                batch.draw(new Texture("flame.png"), x * Settings.SCALED_TILE_SIZE, 
                ((y - i) * Settings.SCALED_TILE_SIZE), Settings.SCALED_TILE_SIZE, 
                Settings.SCALED_TILE_SIZE);
            }
        }
    }

}

public void Boom() {
    bomb_explode = false;
    for(int i = 0; i <= 1; i++) {
        if(map.getTile(x, y).getPlayer() != null) {
            map.getTile(x, y).getPlayer().Die();
        }

        if(x + i <= map.getWidth() && map.getTile(x+i, y).getPlayer() != null) {
            map.getTile(x+i, y).getPlayer().Die();
        }

        if(x - i >= 0 && map.getTile(x-i, y).getPlayer() != null) {
            map.getTile(x-i, y).getPlayer().Die();
        }

        if(y + i <= map.getHeight() && map.getTile(x, y+i).getPlayer() != null) {
            map.getTile(x, y+i).getPlayer().Die();
        }

        if(y - i >= 0 && map.getTile(x, y-i).getPlayer() != null) {
            map.getTile(x, y-i).getPlayer().Die();
        }
    }
    bombs.remove(this);
}

public void createTimer() {
    timeLeft = 0;
    task = new TimerTask() {

        @Override
        public void run() {
            ++timeLeft;
            if(timeLeft > 3) {
                bomb_explode = true;
                Boom();
                clearTimer();
            }
        }
    };

    timer = new Timer();
    timer.schedule(task, 1, 500);
}

public void clearTimer() {
    timer.cancel();
    timer.purge();
    timer = null;
}

In the screen class, I'm rendering the bomb like this :

for(Bomb b : Bomb.bombs) {
    b.render(batch, delta);
}

Here is the error I'm getting:

Exception in thread "LWJGL Application" java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.next(Unknown Source)
at bomberman.screens.GameScreen.render(GameScreen.java:41)
at com.badlogic.gdx.Game.render(Game.java:46)
at bomberman.game.GameObject.render(GameObject.java:23)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:225)
at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:126)

How can I fix it?

I've suggested an edit to add your code to the question directly. You should always post your code using the code formatting block instead of posting a link to a pastebin snippet, in case the link dies in the future. Also, could we have your GameScreen.render() code as well? It seems this is where the problem is located. — Applekini
– Applekini, Commented May 7, 2017 at 15:37
i've added the GameScreen.render() method. Thanks for your time ! — clint rock
– clint rock, Commented May 7, 2017 at 15:48

Community · Accepted Answer · 2017-05-23 12:37:40Z

Your problem (probably) comes from the fact that you call bombs.remove(this); in your bomb's Boom() method while you're iterating through your list. This will throw a ConcurrentModificationException. As stated in the javadocs:

The iterators returned by this class's iterator and listIterator methods are fail-fast: if the list is structurally modified at any time after the iterator is created, in any way except through the iterator's own remove or add methods, the iterator will throw a ConcurrentModificationException.

To circumvent this I quote John Skeet's answer:

Create a list of values you wish to remove, adding to that list within the loop, then call originalList.removeAll(valuesToRemove) at the end
Use the remove() method on the iterator itself. Note that this means you can't use the enhanced for loop.

For you this could look something like this:

// In your Bomb class
public static ArrayList<Bomb> bombs = ...;
public static ArrayList<Bomb> bombsToRemove = ...;

// In your Boom() method
bomb_explode = false;
for(int i = 0; i <= 1; i++) {
    ...
}
bombsToRemove.add(this);

// In your render() method
for(Bomb b : Bomb.bombs) {
    ...
}
Bomb.bombs.removeAll(Bomb.bombsToRemove);
Bomb.bombsToRemove.clear();

Hopefully this resolves the issue for you!

@clintrock if the answer solved your issue make sure to click the "tick" symbol on the answer (top left) to mark it as the correct answer :) — Applekini
– Applekini, Commented May 7, 2017 at 17:03

Stack Exchange Network

LibGDX Bomberman bomb arraylist iterator error

1 Answer 1

You must log in to answer this question.

Hot Network Questions

LibGDX Bomberman bomb arraylist iterator error

1 Answer 1

You must log in to answer this question.

Related

Hot Network Questions