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:

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;
    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;
            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;
            while (pos>0) {
                previousNode = currentNode;
                currentNode = currentNode.next;
            return true;
            public boolean validPos()
                return ((_pos>=1 && (_pos<= _len)));


            public ItemType getItem() {
                     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)


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