# Struggling to figure out solution to fix IndexOutOfBoundsException

**URL:** <https://discourse.processing.org/t/struggling-to-figure-out-solution-to-fix-indexoutofboundsexception/40603>\
**Category:** Coding Questions\
**Created:** [January 16, 2023, 4:43am UTC](https://discourse.processing.org/t/struggling-to-figure-out-solution-to-fix-indexoutofboundsexception/40603 "2023-01-16T04:43:41Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Mr\_Derp\_Face](https://avatars.discourse-cdn.com/v4/letter/m/858c86/32.png) [@Mr\_Derp\_Face](https://discourse.processing.org/u/Mr_Derp_Face)\
**Post date:** [January 16, 2023, 4:43am UTC](https://discourse.processing.org/t/struggling-to-figure-out-solution-to-fix-indexoutofboundsexception/40603/1 "2023-01-16T04:43:42Z")

</div>

I am working on a project where you have to shoot an enemy. Unfortunetly when the bullet hits the enemy if only one shot is currently active it will throw `IndexOutOfBoundsException`. I am lost on what to do the remedy this so your help is appriciated.

```auto
if(bullets.size() > 0) {
    for(int i = 0; i < bullets.size(); i++) {
         if(shootingEnemys.size() > 0) {
             for(int j = 0; j < shootingEnemys.size(); j++) {
                 if((bullets.get(i).x >= shootingEnemys.get(j).x - 25) && (bullets.get(i).x <= shootingEnemys.get(j).x + 25) && (bullets.get(i).y >= shootingEnemys.get(j).y - 25) && (bullets.get(i).y <= shootingEnemys.get(j).y + 25)) {
                     shootingEnemys.remove(j);
                     bulletSprite = loadImage("Bullet_Hit.png");
                     bulletSprite.resize(20, 20);
                     score += 200;
                     bullets.remove(i);
                }
            }
        }
    }
}

```

thank you again for your help

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<div class="post-metadata">

**Author:** ![Chrisir](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/chrisir/32/45_2.png) [@Chrisir](https://discourse.processing.org/u/Chrisir)\
**Post date:** [January 16, 2023, 5:41am UTC](https://discourse.processing.org/t/struggling-to-figure-out-solution-to-fix-indexoutofboundsexception/40603/2 "2023-01-16T05:41:04Z")

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One reason could be that you use `remove()`.  
Better is to set a marker `isDead = true;` (which is a new variable in the class).

Then in two separate for loops (after the current loops), go backwards through the arrays using  
`for(int j...` and say  
`if (shootingEnemys.get(j).isDead) shootingEnemys.remove(j);`

(Processing doesn’t like `remove()` when going through an `ArrayList` forward)

**Remark**

> [@Mr\_Derp\_Face](#):
>
> ```auto
> bulletSprite = loadImage("Bullet_Hit.png");
> bulletSprite.resize(20, 20);
> 
> ```

Not sure why you do this here? It should be in `setup()`. Both commands are very processor costly.  
(Just as a remark)

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<div class="post-metadata">

**Author:** ![grshch](https://avatars.discourse-cdn.com/v4/letter/g/ed8c4c/32.png) [@grshch](https://discourse.processing.org/u/grshch)\
**Post date:** [January 16, 2023, 3:04pm UTC](https://discourse.processing.org/t/struggling-to-figure-out-solution-to-fix-indexoutofboundsexception/40603/3 "2023-01-16T15:04:19Z")

</div>

First, when you remove items from an ArrayList in a loop you should loop it backwards. Otherwise, you skip items next to the removed ones. For example, if you delete an item with index 2, then the next shifts to its place and you jump over it to index 3.

Second, you don’t really need to check the length of the ArrayLists like that. If it’s 0 your loops will do it for you, since 0 \< 0 is a false statement.

UPD. Got it. Looks like the error appears because you are deleting enemies and bullets in the same loop. It is possible that you deleted all the items from one of the lists but still trying to check them in that long condition. Using ‘isDead’ property as @Chrisir described will help.