# Help with a short game code
**URL:** https://discourse.processing.org/t/help-with-a-short-game-code/11108
**Category:** Coding Questions
**Created:** [May 10, 2019, 2:54pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108 "2019-05-10T14:54:23Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@majR](https://discourse.processing.org/u/majR)
#### Post date: [May 10, 2019, 2:54pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108/1 "2019-05-10T14:54:23Z")
when i try to remove a part of a arraylist it says the error “ConcurrentModificationException”
here is the file : [https://drive.google.com/open?id=1-NATnwPv0Qw3abEjZzP8rBFMXgwngVrL](https://drive.google.com/open?id=1-NATnwPv0Qw3abEjZzP8rBFMXgwngVrL)
here is what gives the error
```auto
for(Laser actualLaser: laserList){
println(actualLaser);
for(int i = 0; i<4; i++){
if(actualLaser.x > escudoArray[i].x-50 &&
actualLaser.x < escudoArray[i].x+50 &&
actualLaser.y > escudoArray[i].y-5 &&
actualLaser.y < escudoArray[i].y+5 &&
actualLaser.vel > 0){
escudoArray[i].y = -500;
laserList.remove(actualLaser);
}
}
```
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [May 10, 2019, 3:56pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108/2 "2019-05-10T15:56:32Z")
We can’t use method **remove()** when using an “enhanced” `for ( : ) {}` style! 🚫
Use a vanilla `for ( ; ; ) {}` style instead. Preferably, w/ backwards iteration: 🔙
> [@\[SOLVED\] Py.processing bullet and enemy collision](https://discourse.processing.org/t/solved-py-processing-bullet-and-enemy-collision/8327/4):
>
> @solub, your solution is buggy! bug When we delete an item from a list, all elements w/ a higher index than the deleted item got their indices subtracted by 1! face_with_monocle They’re left-shifted, and therefore, the next iteration skips an item; which now got the same index as the just deleted item. arrow_left You can see that bug in this sample loop below: eye : nums = list(range(10)) # [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] for n in nums: print n nums.remove(n) print nums # [1, …
---
### Author:  [@hotfooted](https://discourse.processing.org/u/hotfooted)
#### Post date: [May 10, 2019, 4:12pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108/3 "2019-05-10T16:12:18Z")
couldn’t you use an iterator as well? something like
```auto
Iterator it = myList.iterator();
while (it.hasNext()) {
if ("SOMESTRING".equals(it.next())) {
it.remove();
}
}
```
might be slower on larger lists and i gotta say a for loop running n-0 is my preferred way too but the more options the better…right 😕
---
### Author:  [@GoToLoop](https://discourse.processing.org/u/GoToLoop)
#### Post date: [May 10, 2019, 4:17pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108/4 "2019-05-10T16:17:05Z")
> [@hotfooted](#):
>
> Couldn’t you use an Iterator as well?
The reason I prefer not to rely on an Iterator is b/c it’s incompatible w/ Pjs, in case I decide to deploy my sketch online as well. 🕸
---
### Author:  [@hotfooted](https://discourse.processing.org/u/hotfooted)
#### Post date: [May 10, 2019, 4:21pm UTC](https://discourse.processing.org/t/help-with-a-short-game-code/11108/5 "2019-05-10T16:21:02Z")
well that makes sense.