hi i have used three classes to make link list in java lean list as interface, Basic list got the constructor etc , and Demo basic test i need the function to be added in the demo basic list to complete the program.
the following code for classes are as follows:

leanlist
interface LeanList<ItemType> 
{
public static final int MAX_LENGTH=10;

public boolean insertItem(ItemType newItem);
public boolean deleteItem();
public boolean advance();
public boolean retreat();
public boolean jumpTo(int pos);
public boolean validPos();
public int Length();
public  ItemType getItem();

}

Basic List

public class BasicList <ItemType> implements LeanList <ItemType> 
{
private int _pos= 0;
private int _len= 0;
private final ListNode _root = new ListNode((ItemType)null);
private ListNode currentNode = _root;
private ListNode previousNode;


public BasicList() {}

public boolean insertItem(ItemType newItem) {
    if ((_pos<=0) || (_len== MAX_LENGTH))
    return false;

    ListNode newNode = new ListNode(newItem);
    ListNode LeftNode = previousNode;
    ListNode RightNode = currentNode;
    currentNode = newNode;
    previousNode = LeftNode;
    LeftNode.next = newNode;
    newNode.previous = LeftNode;

    if(RightNode !=null) {
        newNode.next = RightNode;
        RightNode.previous = currentNode;
    }
    _len++;
    return true;

    }
    public boolean ValidPos() {
        return((_pos>=1 && (_pos<= _len))) ; 

    }

        public boolean deleteItem() {
            if((!validPos()) || (_len==0)) return false ;
            ListNode leftNode = previousNode;
            ListNode rightNode = currentNode.next;
            leftNode.next = rightNode;

            if(rightNode!= null)
                rightNode.previous = leftNode;
            currentNode = rightNode;
            _len--;
            return true;

        }
        public boolean advance() {
            if(_pos == _len+1) return false;
            return jumpTo (_pos+1);


        }
        public boolean retreat() {
            if(_pos==0) return false;
            return jumpTo(_pos-1);
        }

        public boolean jumpTo(int pos) {
            if((_pos<0) || (pos>_len+1)) return false ;
            currentNode = _root;
            _pos=pos;
            while (pos>0) {
                previousNode = currentNode;
                currentNode = currentNode.next;
                _pos--;
            }
            return true;
}
            public boolean validPos()
            {
                return ((_pos>=1 && (_pos<= _len)));

        }

            public ItemType getItem() {
                 if(currentNode==null) 
                     return null;
                 return (ItemType) currentNode.itm;     
            }



            public int Length() {
                return _len;
            }


            public class ListNode 
            {
                private ItemType itm;
                private ListNode previous;
                private ListNode next;

                public ListNode(ItemType item){
                    this.itm = item;

                    }
                public ListNode getPrevious() {
                    return previous;
                }

                public ListNode setPrevious(ListNode previous) {
                return this.previous = previous;

            }
            public ListNode gotNext() {
                return next;

            }
            public void setNext(ListNode next) {
                this.next = next ;
            }
            public ItemType getIem() {
                return itm;

            }


            }
            public void display() {
                ListNode node = _root;
                while( (node = node.next)!= null)
                    System.out.println(node.itm);
                System.out.println();

            }
        }

DemoBasic List plz help me in adding the required functions in this class.. thank you

public class DemoBasicTest
{

    public static void main(String [] args){
        BasicList<Integer> list = new BasicList<Integer>();

}
}

hullo can nyone help me writing this code.. i need to submit my assignment urgently.. thank you