CircularLinkedList.... Ahhh

Question

So, I managed to make a LinearLinkedList and DoublyLinkedList without any problems. However, I'm currently making a CircularLinkedList and I need a little help. I can't get the implementation for Object removeFirst() and Object removeLast(). Now, I want to finish this without resorting to making a CircularDoublyLinkedList, so I can't put a getPrev() method in. Anyway, here is the code!
Here is the interface first of all. Most of the comments comes from the book that I am reading with.
ListNode.java
     * The "value" data field is of type "Object," which means that primitive types like "int"
     * cannot be placed directly into a ListNode. They must first be wrapped in a wrapper class like
     * "Integer."
    private Object value;
     * The ListNocde class is said to be "self-referential," since it has an instance variable
     * "next" that refers to itself. Self-referential objects can be linked together to form objects
     * like lists, trees, stacks, and so on. Thus the variable "next" is called a "link" or
     * "pointer."
    private ListNode next;
     * The ListNode constructor, with initValue and initNext parameters, allows a single statement
     * to assign the "value" and "next" fields to a ListNode.
     * @param initValue sets the value of this node
     * @param initNext sets value of the next node
    public ListNode(Object initValue, ListNode initNext)
        value = initValue;
        next = initNext;
     * This is an accessor method that returns the value of the current ListNode. Since the type is
     * Object, a cast to "Integer, Double, or String," and so on will be needed, unless you plan to
     * assign it to a variable of type Object.
     * @return the value of this node
    public Object getValue()
        return value;
     * This is an accessor method that returns "next," the pointer value of the the current
     * ListNode.
     * @return the value of the next node
    public ListNode getNext()
        return next;
     * This is a mutator method that allows the "value" of the current ListNode to be changed to
     * "theNewValue."
     * @param theNewValue the new value of the node
    public void setValue(Object theNewValue)
        value = theNewValue;
     * This is a mutator method that allows the "next" field of the current ListNode to be changed
     * to "theNewNext."
     * @param theNewNext the new pointer value of the next node
    public void setNext(ListNode theNewNext)
        next = theNewNext;
}And here is the CircularLinkedList.java
import java.util.NoSuchElementException;
public class CircularLinkedList
    private ListNode lastNode;
    private int size;
    //Construct an empty list
    public CircularLinkedList()
        size = 0;
        lastNode = null;
    //Return true if list is empty, false otherwise
    public boolean isEmpty()
        return size == 0;
        //or return lastNode == null;
    //Return number of nodes in the list
    public int size()
        return size;
    //This method is needed for client traversal of list.
    //Returns reference to first node
    public ListNode getlastNode()
        return lastNode;
    //Insert Object obj at front of list
    public void addFirst(Object obj)
        if(isEmpty())
            lastNode = new ListNode(obj, null);
            lastNode.setNext(lastNode);
        else
            ListNode p  = new ListNode(obj, lastNode.getNext().getValue());
            lastNode.setNext(p);
        size++;
    //Insert Object obj at end of list
    public void addLast(Object obj)
        if(isEmpty())
            lastNode = new ListNode(obj, null);
            lastNode.setNext(lastNode);
        else
            ListNode p = new ListNode(obj, lastNode.getNext().getValue());
            lastNode.setNext(p);
            lastNode = p;
        size++;
    //Remove and return first element
   public Object removeFirst()
        if(isEmpty())
            throw new NoSuchElementException("Can't remove from empty list");
        //what goes in here?
        size--;
        return item;
    //Remove and return last element
    public Object removeLast()
        if(isEmpty())
            throw new NoSuchElementException("Can't remove from empty list");
    //what goes in here?
        size--;
    //Return CircularLinkedList as String
    public String toString()
        if(isEmpty())
            return "empty.";
        else
            String s = "";
            ListNode current = lastNode.getNext();
            while(current != lastNode)
                s = s + current.getValue() + " ";
                current = current.getNext();
            s = s + current.getValue();
            return s;
}Thanks in advance guys!

Answer 1

ok yjis is the code but is not well codified so is a kinf�d of messy, But it works.
public class Node {
    public Node next;
    private int data;
    /** Creates new Node */
    public Node(int info) {
        data=info;
    public String Print () {
        return ("\nData: "+data);
public class List {
   Node ini;
    /** Creates new List */
    public List() {
        ini=null;
    public void AddFirst (int info) {
        Node temp=ini;
        Node NewNode=new Node (info);
        if (ini!=null) {
            while (temp.next!=ini)
                temp=temp.next;
            NewNode.next=ini;
            temp.next=NewNode;
            ini=NewNode;
        if (ini==null) {
            ini=NewNode;
            NewNode.next=ini;
    public Node DelFirst () {
        Node behind=ini;
        if (ini==null) return null;
        if (ini!=null) {
            if (ini.next==ini) {
                ini=null;
                return ini;
            if (ini.next!=ini) {
                while (behind.next!=ini) {
                    behind=behind.next;
                ini=ini.next;
                behind.next=ini;
        return ini;
    public Node DelLast () {
        if (ini==null) return null;
        Node temp=ini;
        Node behind=null;
        if (ini!=null) {
            if (ini.next==ini) {
                ini=null;
                return ini;
            if (ini.next!=ini) {
                while (temp.next!=ini) {
                    behind=temp;
                    temp=temp.next;
                behind.next=temp.next;
                temp.next=null;
        return temp;
    public String Print () {
        String res="";
        Node temp=ini;
        if (temp!=null) {
            res=res+temp.Print ();
            while (temp.next!=ini) {
                temp=temp.next;
                res=res+temp.Print ();
        return res;
public class Test extends java.applet.Applet {
    List Lista;
    /** Initializes the applet Test */
    public void init() {
        Lista=new List ();
        initComponents();
    /** This method is called from within the init() method to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
    private void initComponents() {
        txt = new java.awt.TextField();
        label1 = new java.awt.Label();
        ins = new java.awt.Button();
        delf = new java.awt.Button();
        dell = new java.awt.Button();
        button4 = new java.awt.Button();
        Area = new java.awt.TextArea();
        setLayout(null);
        add(txt);
        txt.setBounds(140, 70, 40, 20);
        label1.setText("Number: ");
        add(label1);
        label1.setBounds(80, 70, 55, 20);
        ins.setLabel("Insert");
        ins.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                insMouseReleased(evt);
        add(ins);
        ins.setBounds(80, 110, 60, 24);
        delf.setLabel("Del first");
        delf.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                delfMouseReleased(evt);
        add(delf);
        delf.setBounds(80, 140, 60, 24);
        dell.setLabel("Del last");
        dell.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                dellMouseReleased(evt);
        add(dell);
        dell.setBounds(80, 170, 60, 24);
        button4.setLabel("Print");
        button4.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                button4MouseReleased(evt);
        add(button4);
        button4.setBounds(80, 200, 60, 24);
        add(Area);
        Area.setBounds(160, 110, 150, 110);
    private void button4MouseReleased(java.awt.event.MouseEvent evt) {
        // Add your handling code here:
        Area.setText (""+Lista.Print ());
    private void dellMouseReleased(java.awt.event.MouseEvent evt) {
        // Add your handling code here:
        Lista.DelLast ();
    private void delfMouseReleased(java.awt.event.MouseEvent evt) {
        // Add your handling code here:
        Lista.DelFirst ();
    private void insMouseReleased(java.awt.event.MouseEvent evt) {
        // Add your handling code here:
        Lista.AddFirst (Integer.parseInt (txt.getText()));
    // Variables declaration - do not modify
    private java.awt.TextField txt;
    private java.awt.Label label1;
    private java.awt.Button ins;
    private java.awt.Button delf;
    private java.awt.Button dell;
    private java.awt.Button button4;
    private java.awt.TextArea Area;
    // End of variables declaration
-----------------------------------------and the html
<HTML>
<HEAD>
   <TITLE>Applet HTML Page</TITLE>
</HEAD>
<BODY>
<H3><HR WIDTH="100%">Applet HTML Page<HR WIDTH="100%"></H3>
<P>
<APPLET codebase=.. code="CircularList/Test.class" width=350 height=200></APPLET>
</P>
<HR WIDTH="100%"><FONT SIZE=-1><I>Generated by NetBeans IDE</I></FONT>
</BODY>
</HTML>