Is Iterator class really necessary for our lifes?

Question

I'm reading about Iterator class and how to use it, but a doubt arrise. Is it really necessary?
Take a look at my code bellow:
import java.util.*;
public class Main {
    public static void main(String[] args) {
        ArrayList ar = new ArrayList();
        for (int i=0;i<20;i++)
            ar.add(i);
        //Method 1
         for(int i=0;i<ar.size();i++)
            if (((Integer)ar.get(i) % 2) != 0)
                ar.remove(i);
        //Method 2
        Iterator it = ar.iterator();
        while(it.hasNext())
            if (((Integer)it.next() % 2) != 0)
                it.remove();
        System.out.println("The even numbers are: ");
        for(int i=0;i<ar.size();i++)
            System.out.println((Integer)ar.get(i));
}In the code above, we have two ways to do the same thing, both works fine, but using the Method 2 I needed to code one line more instancing a new class Iterator.
Can anyone tell me in which circuntances I really need to use a Iterator and why?
Thanks

Answer 1

Additionally, Iterator works on all Collections. For Sets, there is no get(i). If you have a method that returns a Collection, and that Collection might be a LinkedList or an ArrayList or a HashSet or something else, the Iterator is the gauranteed way to walk through it, regardless of what class it is. And with enhanced for loop, it's quite clean and simple.
Collection<Thing> things = thingFetcher.fetchACollectionOfThings(); // LinkedList? HashSet? We don't know and don't care
for (Thing thing : things) {
  thing.doStuff();
}