Node and List

Question

Hi,
I need to shuffle and merge 2 list that would be enter by the user. I have created 2 classes, Node and List class(from references) and a test class to do my algo.
(in my list class, I would stop adding the node behind when user entered 9999)
Eg:
Enter first List: 1 2 3 9999
Enter second List : 4 5 6 7 9999
I would need to get the result as
1 4 2 5 3 6 7
Which mean, the newlist will get the head of the firstlist and set its next to the head of second list. And back to the 2 element of first list then 2nd element on second list and so on.
my code is shown below. After some debugging, I noted that my c1 would changed if I changed c3. I do not know how to express myself and question well in words. Hope anyone can help and assist.
Thanks alot.
import java.io.*;
// A class of Node which allows us to construct
// a node
// This defines a ?normal node? (type).
public class Node {
private Object item;
private Node next;
// This defines a node at the end of the list.
public Node(Object newItem) {
item = newItem;
next = null;
} // Constructor
// This is to create a ?normal? node.
public Node(Object newItem, Node nextNode) {
item = newItem;
next = nextNode;
} // Constructor
// This is to update the item field of a node.
public void setItem(Object newItem) {
item = newItem;
} // end setItem
// This is to read the item field of a node.
public Object getItem() {
return item;
} // end getItem
// This is to update the next field of a node.
public void setNext(Node nextNode) {
next = nextNode;
} // end nextNode
// This is to read the next field of a node
public Node getNext() {
return next;
} // end getNext()
} // end class NodeList Class
public class List {
Node head;
public void initilise() {
head = null;
public boolean empty() {
return (head==null);
public void addOneNodeAfter(Node p, Node newNode) {
newNode.setNext(p.getNext());
p.setNext(newNode);
// unnecessary
public void addOneNodeBefore(
Node previous, Node p, Node newNode) {
previous.setNext( newNode);
newNode.setNext(p);
public void addOneNodeBeforeHead(Node newNode) {
newNode.setNext(head);
head = newNode;
public void deleteOneNodeAfter(Node p) {
p.setNext( p.getNext().getNext());
public void printList(Node p){
   p.setNext( p.getNext().getNext());
void constructListFront(){
    Scanner input=new Scanner(System.in);
    int x = input.nextInt();
    Node p = new Node(x);
    while (x !=9999){
        addOneNodeBeforeHead(p);
        x = input.nextInt();
        p = new Node(x);
Node tail(){
    Node p = head;
    while (p.getNext() != null){
        p = p.getNext();
    }return p;
void constructTail(){
    Scanner input =new Scanner(System.in);
    int x = input.nextInt();
    Node p = new Node(x);
    Node t = tail();
    while ( x != 9999){
     addOneNodeAfter(t,p);
     t = t.getNext();
     x = input.nextInt();
     p = new Node(x);
void printList(){
    Node p = head;
    while ( p != null){
        System.out.printf(" "+ p.getItem());
        p = p.getNext();
    System.out.println();
int getLength(){
    int length =0;
    Node p = head;
     p = p.getNext();
    while ( p != null){
        length = length + 1;
        p = p.getNext();
    return length;
}Lastly, My test class
public class test {
   public static void main(String[] args) {
List shortList = new List();
List longList = new List();
System.out.println("Enter first list");
shortList.constructListFront();
System.out.println("Enter second list");
longList.constructListFront();
    List newList = new List();
     Node c1 =  shortList.head;
    Node c2 = longList.head;
    Node c3 = shortList.head;
newList.head = c3;
c3.setNext(c2);
c3 = c3.getNext();
c1 = c1.getNext();
c2 = c2.getNext();
while ( c1 != null){
    c3.setNext(c1);
    c3=c1;
    c3.setNext(c2);
    c3 = c2;
    c1 = c1.getNext();
    c2 = c2.getNext();
c3.setNext(c2);
shortList.printList();
longList.printList();
newList.printList();
   }

Answer 1

seah_ly wrote:
Hi,
My question is, I have manage to get 2 list, shortList and longList. But, how can I created another newList which contain alternate element from shortList and longList.
thanks a lot.
* Merge elements from ListA and ListB in parallel into MainList
while(ListA.head != null && ListB.head != null) {
  //Reference to head of ListA
  Node nodeA = listA.head;
  //Make new head of ListA the next element in the list.
  listA.head = listA.next();
  //Set the next element of nodeA to null, we only want to add the single element, not its links
  nodeA.next() = null;
  //Add the element
  MainList.addTail(nodeA);
  Node nodeB = listB.head;
  listB.head = listB.next();
  nodeB.next() = null;
  MainList.addTail(nodeB);
//Either both lists heads are null or exclusive or list head is not null, so add head and it's corresponding links to list.
if(ListA.head != null) {
  MainList.addTail(ListA.head);
} else if(ListB.head != null) {
  MainList.addTail(ListB.head);
}Mel