Cursor(int index) 
{
          
            super(index);
            _valid = true;
            registerCursor(this);
}

 public  void add(Object o) 
{
            checkForComod();
            Listable elt = insertListable(_cur.prev(),_cur.next(),o);
            _cur.setPrev(elt);
            _cur.setNext(elt.next());
            _lastReturned = null;
            _nextIndex++;
            _expectedModCount++;
}

 protected  void checkForComod() 
{
            if(!_valid) {
                throw new ConcurrentModificationException();
            }
}

 public  void close() 
{
            if(_valid) {
                _valid = false;
                unregisterCursor(this);
            }
}

Mark this cursor as no longer being needed. Any resources associated with this cursor are immediately released. In previous versions of this class, it was mandatory to close all cursor objects to avoid memory leaks. It is no longer necessary to call this close method; an instance of this class can now be treated exactly like a normal iterator.

 protected  void invalidate() 
{
            _valid = false;
}

 protected  void listableChanged(CursorableLinkedList.Listable elt) 
{
            if(_lastReturned == elt) {
                _lastReturned = null;
            }
}

 protected  void listableInserted(CursorableLinkedList.Listable elt) 
{
            if(null == _cur.next() && null == _cur.prev()) {
                _cur.setNext(elt);
            } else if(_cur.prev() == elt.prev()) {
                _cur.setNext(elt);
            }
            if(_cur.next() == elt.next()) {
                _cur.setPrev(elt);
            }
            if(_lastReturned == elt) {
                _lastReturned = null;
            }
}

 protected  void listableRemoved(CursorableLinkedList.Listable elt) 
{
            if(null == _head.prev()) {
                _cur.setNext(null);
            } else if(_cur.next() == elt) {
                _cur.setNext(elt.next());
            }
            if(null == _head.next()) {
                _cur.setPrev(null);
            } else if(_cur.prev() == elt) {
                _cur.setPrev(elt.prev());
            }
            if(_lastReturned == elt) {
                _lastReturned = null;
            }
}

 public int nextIndex() 
{
            throw new UnsupportedOperationException();
}

 public int previousIndex() 
{
            throw new UnsupportedOperationException();
}