Space Invaders ArrayList IndexOutOfBoundsException

Question

Okey, I've searched for this error and found out that the cause is probably that my update of the Arraylist is somehow conflicting with my repaint() method. I have changed my code many times trying to fix it but either I can't compile or I end up with the exact same error. I am creating Space Invaders and the game runs fine until I shoot to fast (ie. tap the UP button to fast) and this error comes up: (NB:the x in "Index: x, Size: x" is not always 1 it has ranged from 1 to 6)

Exception in thread "AWT-EventQueue-0" java.lang.IndexOutOfBoundsException: Index: 1, Size: 1
at java.util.ArrayList.rangeCheck(ArrayList.java:604)
at java.util.ArrayList.get(ArrayList.java:382)
at Board.checkCollisions(Board.java:185)
at Board.actionPerformed(Board.java:172)
at javax.swing.Timer.fireActionPerformed(Timer.java:312)
at javax.swing.Timer$DoPostEvent.run(Timer.java:244)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:251)
at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:733)
at java.awt.EventQueue.access$200(EventQueue.java:103)
at java.awt.EventQueue$3.run(EventQueue.java:694)
at java.awt.EventQueue$3.run(EventQueue.java:692)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(ProtectionDomain.java:76)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:703)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:146)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:138)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:91)

Here is the part of the code that seems to cause the problem.

        public void actionPerformed(ActionEvent e){
    if(enemies.size() == 0){
        ingame = false;
    }

    ArrayList ss = gun.getShots();

    for(int i = 0; i < ss.size(); i++){
        Shot s = (Shot) ss.get(i);
        if(s.isVisible()){
            s.move();
        }
        else{
            ss.remove(i);
        }
    }

    for(int i = 0; i < enemies.size(); i++){
        Enemy en = (Enemy) enemies.get(i);
        if(en.isVisible()){
            en.move();
        }
        else{
            enemies.remove(i);
        }
    }

    for(int i = 0; i < bunkers.size(); i++){
        Bunker b = (Bunker) bunkers.get(i);
        if(b.isVisible() == false){
            bunkers.remove(i);
        }
    }

    gun.move();
    checkCollisions();
    repaint();
}

public void checkCollisions(){

    ArrayList ss = gun.getShots();

    for(int i = 0; i < ss.size(); i++){
        Shot s = (Shot) ss.get(i);
        Rectangle r1 = s.getBounds();
        //Collision for Enemies
        for(int j = 0; j < enemies.size(); j++){
            Enemy en = (Enemy) enemies.get(i);
            Rectangle r2 = en.getBounds();

            if(r1.intersects(r2)){
                s.setVisible(false);
                en.setVisible(false);
            }
        }
        //Collision for Bunker
        for(int j = 0; j < bunkers.size(); j++){
            Bunker b = (Bunker) bunkers.get(i);
            Rectangle r2 = b.getBounds();

            if(r1.intersects(r2)){
                s.setVisible(false);
                b.setVisible(false);
                score++;
            }
        }

    }
}

More specifically these lines of code:

checkCollisions();
Enemy en = (Enemy) enemies.get(i);

and sometimes

checkCollisions();
Bunker b = (Bunker) bunkers.get(i);

Also there is another problem. For some reason when I shoot the aliens or when I shoot at the bunker I always have to shoot the one that is first in the ArrayList for it too disappear. If I shoot the others first nothing happens, the shot just flies through them. This is not my primary concern so I understand if you do not want to waste time explaining that to me. Thanks in advance.

Answer 1

I guess that these two snippets are the problem:

    for(int j = 0; j < enemies.size(); j++){
        Enemy en = (Enemy) enemies.get(i);


    for(int j = 0; j < bunkers.size(); j++){
        Bunker b = (Bunker) bunkers.get(i);

You iterate with j, but you use i in the getter.

Answer 2

Here is the part of the code that seems to cause the problem.

There's no need to guess as the exception stacktrace should tell you exactly which line causes the exception. If you post a similar problem, you will want to indicate to us which line is causing the problem, here it is at Board.checkCollisions(Board.java:185), or line 185 of Board.java.

This code looks suspicious:

for(int i = 0; i < bunkers.size(); i++){
    Bunker b = (Bunker) bunkers.get(i);
    if(b.isVisible() == false){
        bunkers.remove(i);
    }
}

You're removing an item from a list while iterating forward through it -- something you should not do since it will often cause an AIOOBE like you're seeing. Consider iterating backwards through the collection.