Help me with linkedlist please!!

Question

public void insert(int id, int inv)
Object value = new Item (id, inv);
DoublyListNode temp = new DoublyListNode(null, value, null);
if (size == 0)
addLast(value);
else
DoublyListNode p = first;
while ((p != null) && (((Item)p.getValue()).compareTo(value)) > 0)
p = p.getNext();
if (((Item)first.getValue()).compareTo(value) > 0)
addLast(value);
else
if (((Item)first.getValue()).compareTo(value) < 0)
temp.setPrev(last);
last.setNext(temp);
last = temp;
size++;
else
DoublyListNode tempPtr = first;
while (((Item)tempPtr.getNext().getValue()).compareTo(value) < 0)
tempPtr = tempPtr.getNext();
temp.setPrev(tempPtr);
temp.setNext(tempPtr.getNext());
tempPtr.setNext(temp);
temp.getNext().setPrev(temp);
size++;
why is my insertion method does the same thing as the addLast?
the list is in it's original order..

Answer 1

Singly linked list implementation using a dummy head. I haven't implemented a delete method, I'll leave that up to you :)
public class Test {
    public static void main (String[] parameters) {
        LinkedList list = new LinkedList ();
        list.add ("0");
        list.add ("2");
        list.insert ("1", 1);
        System.out.println (list);
    private static class LinkedList {
        private Node head;
        private int size;
        public LinkedList () {
            head = new Node (null); // dummy
            size = 0;
        public boolean isEmpty () {
            return head.getNext () == null;
        public void clear () {
            head.setNext (null);
        public void add (Object value) {
            insert (value, size);
        public void insert (Object value, int index) {
            Node node = getNode (index - 1);
            node.setNext (new Node (value, node.getNext ()));
            size ++;
        public Object get (int index) {
            return getNode (index).getValue ();
        /* note that index can be -1: that's the (dummy) head */
        private Node getNode (int index) {
            if (index < -1 || index >= size) {
                throw new IndexOutOfBoundsException ();
            Node node = head;
            int i = -1;
            while (i < index) {
                node = node.getNext ();
                i ++;
            return node;
        public String toString () {
            return isEmpty () ? "" : head.getNext ().toString ();
        private class Node {
            private Object value;
            private Node next;
            public Node (Object value) {
                this (value, null);
            public Node (Object value, Node next) {
                this.value = value;
                this.next = next;
            public Object getValue () {
                return value;
            public void setNext (Node next) {
                this.next = next;
            public Node getNext () {
                return next;
            public String toString () {
                return value + ((next == null) ? "" : ", " + next);
}Hope this helps.