IndexOutOfBoundsException when removing ArrayList element

Question

I have this code right here (using lwjgl but that should be moot) to try and pause a game when pressing the esc key. I use an ArrayList with the keys to keep track of what is pressed and what isn't.

public List<Integer> keys = new ArrayList<Integer>();

public void get() {
    if (isKeyDown(KEY_ESCAPE) && !keys.contains(KEY_ESCAPE)) {
        keys.add(KEY_ESCAPE);
        keyEscape();
    }
}

public void rem() {
    if (!isKeyDown(KEY_ESCAPE) && keys.contains(KEY_ESCAPE))
        keys.remove(KEY_ESCAPE);
}

private void keyEscape() {
    Screen.paused ^= true;
}

This is called by the loop, which does get() and rem() one right after another in the loop, in that order. This gives me an awesome java.lang.IndexOutOfBoundsException: Index: 1, Size: 1 at keys.remove(KEY_ESCAPE); when I let go of ESC.

Anyone have any insight to share?

Answer 1

What is the value of KEY_ESCAPE?

It might be int with value 1 so instead of removing the object with that value, you remove the object at position 1 which apparently does not exist.

Answer 2

ArrayList.remove takes an int argument for the index where you want to remove your element. In your case, KEY_ESCAPE also happens to be an Integer.

In short you attempt to remove the Integer value of the escape key as the index of your ArrayList!