Iterate through an ArrayList + Observer Pattern

Question

I have recently tried programming various versions of Iterator and Observer Patterns in Java, but currently I'm stuck at the implementation of both in one project:

What I'm trying to accomplish is to iterate through an ArrayList, which contains elements of type and after each iteration-process to inform the Observer about the change and the containing element. Also I want to be able to choose the "type" of iterator in my separate classes

Edit: I finally finished the project, hopefully this is the correct version of a "Observer Iterator", any tips on how to improve the code are greatly appreciated, but thanks to everybodys' encouraging tips.

Code:

First of all, the helper class for the Observer interface, which implements the update method. Changes with every iteration process and prints out the element.

package iteratorObserver;

import java.util.List;

public class ConcreteObserver implements Observer{

    @Override
    public void update(String element) {
        System.out.println("The current element is: " + element);

    }

}

The actual Observer interface:

package iteratorObserver;

public interface Observer<E> {

    void update(String element);

}

Following that, the same by using a ConcreteSubject and an abstract class Subject The observer pattern requires the getState and setState, so I integrated both into the next method. Getting the element by iterator.next aswell as setting it.

package iteratorObserver;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ConcreteSubject<E>  extends Subject implements IteratorStandardFilter<E>{

    List<String> listElements = new ArrayList<String>();
    private int index;
    private Iterator<E> iterator;

    public ConcreteSubject(Iterator<E> iterator, List<String> listElements){
    index = 0;
    this.iterator = iterator;
    this.listElements = listElements;
    }

    public void addElement(String element) {
        listElements.add(element);
        notifyObservers(element);
    }

    // check the size of the elements list and return if there are still 
    // elements left out
    @Override
    public boolean hasNext() {
        if ((listElements.size() == index))
            return false;
        return true;
    }

    // iterate to the next element, not sure if it's overridden, since the 
    // actual next method of the iterator is still in use
    @Override
    public E next() {
        E result = iterator.next();
        index++;
        notifyObservers((String) result);
        return result;
    }


}

Subject class, only used for the standard observer methods

package iteratorObserver;

import java.util.ArrayList;
import java.util.List;

public class Subject {

    public List<Observer> listObservers = new ArrayList<Observer>();

    public void addObserver(Observer observer){
        listObservers.add(observer);
    }

    public void removeObserver(Observer observer){
        listObservers.remove(observer);
    }

    public <E> void notifyObservers(String element){
        for(Observer observerHelp : listObservers){
            observerHelp.update(element);
        }
    }
 }

Since i want to add various filters, not only the standard list-iterator, i added a class IteratorStandardFilter, as you can see here:

package iteratorObserver;

import java.util.Iterator;

public interface IteratorStandardFilter<E> extends Iterator<E> {

    public boolean hasNext();
    public E next();
}

And finally, the Test method, the main:

package iteratorObserver;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class iteratorObserverMain {

    public static void main(String [] args){

        List<String> listElements = new ArrayList<String>(); 
        listElements.add("hello");
        listElements.add("there");
        listElements.add("everybody");
        listElements.add("it");
        listElements.add("works");
        listElements.add("Thanks for your help. Nice and encouraging forum");

        Iterator<String> iterator = listElements.iterator();
        ConcreteSubject<String> concreteSubject = new ConcreteSubject<String>(iterator, listElements);
        concreteSubject.addObserver(new ConcreteObserver());

        while(concreteSubject.hasNext()){
            concreteSubject.next();
        }

    }
}