anonymous inner class interface

Question

I have this LinkedListDouble class which has the public ListIterator<T>listIterator() method,and I'm trying to execute the interface ListIterator as it's anonymous inner class,am I going the right path?what should I do to make the public int nextIndex()/public int previousIndex() work? nextIndex method returns the index of the element that would be returned by a subsequent call to next, or list size if the list iterator is at the end of the list and the previousIndex method returns the index of the element that would be returned by a subsequent call to previous, or -1 if the list iterator is at the beginning of the list as it said here

here is the LinkedListDouble class

public class LinkedListDouble <T>  {
 private Node first = null;
 private Node last = null;

 public LinkedListDouble ()         // constructor
 {
    first = null;                  // no items on list yet
    last = null;

 }

 public void add(T item) {
     Node newNode = new Node(item);
        if (isEmpty()) {
            first =newNode;
            last = newNode;

        }  
        else {
            //first.setPrev(newNode); 
            //newNode.setNext(first); 
            //first = newNode;

            last.setNext(newNode);
            newNode.setPrev(last);
            last=newNode;
        }
    }
    public boolean contains(T item){
        if(first==null)
            return false;
        else
        {
            Node newNode=first;
            while(newNode!=null)
            {
                if(newNode.getInfo().equals(item))
                    return true;
                else
                    newNode=newNode.getNext();
            }
        }
        return false; 
 }

   public T remove(T item)
    {//get care of first and last nodes
       //and if there is more than 1 matching
        boolean check=contains(item);
        if(check==true)

        {
            Node newNode=first;
            while(newNode!=null)
            {
                if(newNode.getInfo().equals(item))
                {
                    newNode.getPrev().setNext(newNode.getNext());
                    newNode.getNext().setPrev(newNode.getPrev());
                    return item;
                }
                else
                    newNode=newNode.getNext();
            }

        }
        return null;

    }

   public int size()
   {
       int size=0;
       if(first==null)
           return size;
       else
       {

        Node newNode=first;
        while(newNode!=null)
        {
            size++;
            newNode=newNode.getNext();

        }

       }
       return size;
   }

   public String toString()
   {
    Node newNode=first;
    String s="";
    while(newNode!=null)
    {
        s+=newNode.getInfo()+" ,";
        newNode=newNode.getNext();
    }
    return s;

   }

 public boolean isEmpty() {
        return first == null;
    }

and here is the method that should execute the interface ListIterator as it's anonymous inner class and what I tried to do so far:

public ListIterator<T>listIterator() 
 {
     ListIterator<T>listIterator = new ListIterator<T>() {
     private Node current = first;
     private Node temp2 = null;
     private int curindex = 0;

    @Override
    public void add(T e) {
        // TODO Auto-generated method stub
        throw new RuntimeException();
    }

    @Override
    public boolean hasNext() {
        // TODO Auto-generated method stub
        boolean flag=true;
        if(current.getNext()==null)
        {
            flag=false;
        }
        return flag;
    }

    @Override
    public boolean hasPrevious() {
        // TODO Auto-generated method stub
        boolean flag=true;
        if(current.getPrev()==null)
        {
            flag=false;
        }
        return flag;
    }

    @Override
    public T next() {
        // TODO Auto-generated method stub
         if (!hasNext()) throw new NoSuchElementException();


         temp2=current.getNext();
          current=current.getNext();
          return (T) temp2.getInfo();



    }

    @Override
    public int nextIndex() {
        // TODO Auto-generated method stub
        int counter=0;
        if(!hasNext()) return size();
        return curindex;


    }

    @Override
    public T previous() {
        // TODO Auto-generated method stub
         if (!hasPrevious()) throw new NoSuchElementException();

         temp2 = current.getPrev();
         temp2 = temp2.getPrev();


          return (T) temp2.getInfo();
    }

    @Override
    public int previousIndex() {
        // TODO Auto-generated method stub
        int counter=0;
        if(!hasPrevious()) return -1;
        return curindex-1;
    }

    @Override
    public void remove() {
        // TODO Auto-generated method stub
        throw new RuntimeException();
    }

    @Override
    public void set(T e) {
        // TODO Auto-generated method stub
        throw new RuntimeException();
    } 


     };
     return listIterator;
 }

Answer 1

This is a code sample from listIterator() method of LinkedList:

public E next() {
    //check for modification
    if (!hasNext())
        throw new NoSuchElementException();
    lastReturned = next;
    next = next.next;
    nextIndex++;
    return lastReturned.item;
}


public E previous() {
    //check for modification
    if (!hasPrevious())
        throw new NoSuchElementException();
    lastReturned = next = (next == null) ? last : next.prev;
    nextIndex--;
    return lastReturned.item;
}

public int nextIndex() {
    return nextIndex;
}

public int previousIndex() {
    return nextIndex - 1;
}

As you can see, you need to keep an variable like index to keep the track of next index.

The next index is incremented/decremented inside next() and previous() method and these methods already handles List size issue, hence no need to worry about size issue in nextIndex() and previousIndex() method.