stuck on Iterator

Code :

public abstract class AbstractList<E> implements Iterable<E> {
 
    public int indexOf( E elem ) {
      /*This instance method is supposed to find the object E in this list and return its left most occurrence in the list. If the object does not exist within the list then return -1.  */
int counter = 0;
while(this.next != elem)   //this.next = the info part of the node in front "this"
counter++;
    }
return counter;
 
}

What I mean to accomplish is basically to keep my pointer at node1 and check node2 for elem. If elem doesn't exist in node2 then counter goes up and until I find elem in a node counter++

Now the error I get is that next is not a value specified and is not defined for abstract.

So my question is, How can I keep my pointer at the beginning node while checking the next node in the list for elem and returning the index of the node where elem is found.
I can handle the -1 return I expect with a simple if statement.
This is my linkedlist class..

Code :

import java.util.NoSuchElementException;
 
public class LinkedList<E> extends AbstractList<E> {
 
    private static class Node<T> {
 
 private T value;
 private Node<T> next;
 
 private Node( T value, Node<T> next ) {
     this.value = value;
     this.next = next;
 }
    }
 
    private Node<E> first = null;
 
    private class LinkedListIterator implements Iterator<E> {
 
 private Node<E> current;
 
 public boolean hasNext() {
     return ( ( ( current == null ) && ( first != null ) ) || 
       ( ( current != null ) && ( current.next != null ) ) );
 }
 
 public E next() {
 
     if ( current == null ) {
  current = first;
     } else {
  current = current.next;
     }
 
     if ( current == null ) {
  throw new NoSuchElementException();
     }
 
     return current.value;
 }
 
    }
 
    public Iterator<E> Iterator() {
        return new LinkedListIterator();
    }
 
    public int size() {
 
        Node<E> p = first;
        int count = 0;
 
        while ( p != null ) {
            p = p.next;
            count++;
        }
 
        return count;
    }
 
 
    public boolean addFirst( E e) {
 
 boolean added = false;
 
        if ( e != null ) {
 
     first = new Node<E>( e, first );
     added = true;
 
 }
 
        return added;
    }
 
}

Thanks in advance!

Mjall