I understand, thank you for the explanation!

1. This can be changed by making a copy of the input parameter and working on that.

2. The problem with the iterator is that you would need a cyclic iterator, or starting iterating over and over again.

The reason why you should not remove or add an element from a collection while iterating it is the iterating method might throw a Concurrent exception. But the code here only calls for List.size() which is ok.

Removeing items from a list with 'items.remove((int) position)' is bad in two ways:

1. do not modify input parameters
2. it is expensive for LinkedList (seek to the element) or ArrayList (copy a large area)

What do you think about an iterator on a LinkedList?

I'm curious: How can this work?

Isn't removing items from a list forbidden while you are traversing it?
A ConcurrentModificationException should be thrown, and therefore, you would need to use iterators to be able to remove elements from the list you are traversing.

yep still getting this error