Circular Linked List

Hello,
I am working with circular linked Lists. Now the thing is that my assignment was to make this. I had to write a set of methods. Now the thing is that I had to write a method that removes the last value. I made it but it doesnt wark and also i am confused
public Object removeFirst()
         if(size()==0)
            return "empty list";
         Object temp = last.getNext().getValue();
         last.setNext(last.getNext().getNext());
         size--;
         return temp;
      //doesnt Work
       public Object removeLast()
          public Object removeLast()
         if (size()==0)
            return "empty list";
         Object temp= null;
         temp = last.getNext().getValue();
         last = last.getNext();
         size--;
         return temp;
      }

Well what is wrong with the code?
Does it compile?
Does it throw an error at runtime?
Does it give you an unexpected answer?
For solving problems like this with next/prev "pointers" I find diagramming boxes with arrows to help understand is an absolute requirement. Try figuring it out on paper.
If you are removing the last item in the list, that means that the item directly before this one, has to the next one in the list
Assuming you have a structure like this:
...--> (n-1) --> (n) --> (1) --> (2) -->...(n-1)Then removing item (n) you have to make (n-1) point at item (1) as item (n-1) becomes the new "last"
So you have to have the item before the "last" element to keep the next/prev pointers correct.

Similar Messages

Circular Linked List Help

Hi,
I'm developing a circular linked list class.. However everytime I add to the front of the list it overwrites the first element in the list.. I pretty confused at the moment. If anyone could assist me in what I'm doing wrong it would be greatly appreciated..
My Class:
public class CNode<T>
     public T nodeValue;          //data held by the node
     public CNode<T> next;     //next node in the list
     //default constructor; next references node itself
     public CNode()
          nodeValue = null;
          next = this;
     //constructor; initializes nodeValue to item
     //and sets the next to reference the node itself
     public CNode(T item)
          nodeValue = item;
          next = this;
}My addFirst:
public static <T> void addFirst(CNode<T> header, T item)
          CNode<T> curr;
          CNode<T> newNode = new CNode<T>(item);
          //header.next = newNode;
          //newNode.next = header;
          curr = header;
          newNode.next = header;
          curr.next = newNode;
     }

You need a Node class and a class that manages the nodes. The class the manages the nodes is typically called something like MyLinkedList. The MyLinkedList class will typically have a member called 'head' or 'first' and another member called 'last', 'end', or 'tail'. Those members will contain references to the first node and the last node respectively.
The methods like add(), remove(), find(), etc. will be members of the MyLinkedList class--not the Node class. The add() method of the MyLinkedList class will create a node, set the value of the node, and then set the next member to refer to the proper node or null if the node is added to the end of the list. Therefore, there is really no need for a default constructor in the node class. The MyLinkedList class will always set the value of the node, and then set it's next member to refer to something.
You might want to try to write a linear linked list first, and get that working, and then modify it to make it a circular linked list. In addition, you should be drawing pictures of nodes with arrows connecting the different nodes to understand what's going on. Whenver the next member of a node refers to another node, draw an arrow starting at the next member and ending at the node it refers to. The pictures will be especially helpful when you write functions like add().
Message was edited by:
7stud

Circular linked list while loop

i have a circular linked list and i'd like a while loop to iterate though all of them. my problem is that it always excludes the last node. i know why, it's due to the fact that "current.next != alive" skips it from ever accessing the last node. i can't seem to solve it. note that the last node in the list points to the first node (alive):
               while(current.next != alive )
                    prev = prev == null ? prev = alive : prev;
                    //identify the name with it's matching node
                    if(name.equals(current.name.toLowerCase()))
                         prev.next = current.next;
                         dead = current;
                         current = current.next;
                         dead.next = null;
                         while(dead.next != null)
                              dead = dead.next;
                    else
                         prev = current;
                         current = current.next;
               }

//this class assists the client in managing a game of assassinations. it does so by providing options such as verifying a target's existence, getting the list of dead people, getting the lsit of alive people, and moving people from the alive to dead list
public class AssassinManager
     private AssassinNode alive;
     private AssassinNode alive_tail;
     private AssassinNode dead;
     //pre: must send a string array
     //post: nodes are created
     public AssassinManager(String[] names)
          dead = null;
          alive = new AssassinNode(names[0]);
          AssassinNode current = alive;
          System.out.println(names[0] + " is first, " + names[(names.length-1)] + " is last\n\n");
          for(int i = 1; i < names.length; i++)
               while(current.next != null)
                    current = current.next;
               current.next = new AssassinNode(names);
          alive_tail = current.next = new AssassinNode(names[(names.length - 1)], alive);
     //post: outputs all the people still alive
     public void printKillRing()
          AssassinNode last = null, current = alive;
          while(current.next!= alive)
               System.out.println(current.name + " is stalking " + current.next.name);
               last = current.next;
               current = current.next;
          System.out.println(current.name + " is stalking " + alive.name);
     //post: outputs a list of the dead people
     public void printGraveyard()
          AssassinNode last = null, current = dead;
          while(dead != null)
               System.out.println(current.name + " was killed by " + current.killer);
               last = current.next;
               current = current.next;
     //pre: must send a string name
     //post: will return true/false depending on the input if the name is in the killing ring (alive)
     public boolean killRingContains(String name)
          AssassinNode current = alive;
          name = name.toLowerCase();
          while(current.next!= alive)
               if(name.equals(current.name.toLowerCase()))
                    return true;
               current = current.next;
          return false;
     //pre; must send a string name
     //post: will return true/false if the name is in the graveyard list
     public boolean graveyardContains(String name)
          AssassinNode current = dead;
          name = name.toLowerCase();
          while(dead != null && current.next != null)
               if(name.equals(current.name.toLowerCase()))
                    return true;
               current = current.next;
          return false;
     //post: checks if game is over by seeing if there is more than 1 player
     public boolean gameOver()
          AssassinNode current = alive;
          if(current.next == null)
               return true;
          return false;
     //post: outputs the winner's name
     public String winner()
          AssassinNode current = alive;
          if(current.next == null)
               return alive.name;
          return null;
     //pre: must send a string name that exists is alive
     //post: will remove the user from the alive list and add it to the killed list
     public void kill(String name)
          //check if person exists to remove them from alive list
          if(killRingContains(name.trim()) == true)
               AssassinNode prev = null, current = alive, dead = this.dead;
               name = name.toLowerCase();
               while(current != null)
                    System.out.println(current.name);
                    if(name.equals(current.name.toLowerCase()))
                         prev = prev == null ? alive_tail : prev;
                         prev.next = current.next;
                         //dead = dead == null ? current : dead;
                         //while(dead.next != null)
                              //dead = dead.next;
                         if(prev.next == alive)
                              break;
                         current = prev.next;
                    else
                         if(current.next == alive)
                              break;
                         prev = current;
                         current = current.next;
}Edited by: ixxalnxxi on Apr 27, 2008 12:58 AM

How to use circular linked list in pl/sql?

Hi all,
how to use the circular linked list on pl/sql programming.
thanks in advance
Rgds,
B@L@

d balamurugan wrote:
Hi,
I needed this concept for the below example
TABLE_A have the columns of
ID COL_1 COL_2 COL_3 COL_4 COL_5 COL_6 COL_7
1....Y.........N........N.........Y........ N........N........ N
2....N.........N....... N.........Y.........N........N.........Y
in the above data
for id 1 i will need to take the value for COL_4, then i will check the next availability of Y through out through out the remaining columns, so next availability is on COL_1 so, i need to consider COL_4 which already Y and also i need to consider COL_5, COL_6, COL_7 as Y.
for id 2 if i need COL_7 then i need to come back on circular way and need to check the next availability of Y and need to take the columns having N before the next availability of YAnd... even after all that description... you haven't given any indication of what the output should look like.
Taking a wild guess on my part... something like this would do what you appear to be asking...
SQL> ed
Wrote file afiedt.buf
1 with t as (select 1 as id, 'Y' as col1, 'N' as col2, 'N' as col3, 'Y' as col4, 'N' as col5, 'N' as col6,'N' as col7 from dual union all
2             select 2, 'N', 'N', 'N', 'Y', 'N', 'N', 'Y' from dual)
3 --
4 -- END OF TEST DATA
5 --
6 select id
7        ,rcol
8        ,case when instr(cols,'Y',rcol+1) = 0 then instr(cols,'Y')
9              else instr(cols,'Y',rcol+1)
10         end as next_Y_col
11 from   (select id, rcol, col1||col2||col3||col4||col5||col6||col7 as cols
12          from t, (select &required_col as rcol from dual)
13          where id = &required_id
14*        )
SQL> /
Enter value for required_col: 4
old 12:         from t, (select &required_col as rcol from dual)
new 12:         from t, (select 4 as rcol from dual)
Enter value for required_id: 1
old 13:         where id = &required_id
new 13:         where id = 1
        ID       RCOL NEXT_Y_COL
         1          4          1
SQL> /
Enter value for required_col: 7
old 12:         from t, (select &required_col as rcol from dual)
new 12:         from t, (select 7 as rcol from dual)
Enter value for required_id: 2
old 13:         where id = &required_id
new 13:         where id = 2
        ID       RCOL NEXT_Y_COL
         2          7          4
SQL>If that's not what you want... then it's time you started learning how to ask questions properly.

I need help with circular linked list

Hi,
I need help with my code. when I run it I only get the 3 showing and this is what Im supposed to ouput
-> 9 -> 3 -> 7
empty false
9
empty false
3
-> 7
empty false
Can someone take a look at it and tell me what I'm doing wrong. I could nto figure it out.
Thanks.This is my code
/ A circular linked list class with a dummy tail
public class CLL{
     CLLNode tail;
     public CLL( ){
          tail = new CLLNode(0,null); // node to be dummy tail
          tail.next = tail;
     public String toString( ){
     // fill this in. It should print in a format like
     // -> 3 -> 5 -> 7
if(tail==null)return "( )";
CLLNode temp = tail.next;
String retval = "-> ";
     for(int i = 0; i < -999; i++)
do{
retval = (retval + temp.toString() + " ");
temp = temp.next;
}while(temp!=tail.next);
retval+= "";}
return retval;
     public boolean isEmpty( ){
     // fill in here
     if(tail.next == null)
          return true;
     else{
     return false;
     // insert Token tok at end of list. Old dummy becomes last real node
     // and new dummy created
     public void addAtTail(int num){
     // fill in here
     if (tail == null)
               tail.data = num;
          else
               CLLNode n = new CLLNode(num, null);
               n.next = tail.next;
               tail.next = n;
               tail = n;
     public void addAtHead(int num){
     // fill in here
     if(tail == null)
          CLLNode l = new CLLNode(num, null);
          l.next = tail;
          tail =l;
     if(tail!=null)
          CLLNode l = new CLLNode(num, null);
          tail.next = l;
          l.next = tail;
          tail = l;
     public int removeHead( ){
     // fill in here
     int num;
     if(tail.next!= null)
          tail = tail.next.next;
          //removeHead(tail.next);
          tail.next.next = tail.next;
     return tail.next.data;
     public static void main(String args[ ]){
          CLL cll = new CLL ( );
          cll.addAtTail(9);
          cll.addAtTail(3);
          cll.addAtTail(7);
          System.out.println(cll);
          System.out.println("empty " + cll.isEmpty( ));
          System.out.println(cll.removeHead( ));
          System.out.println("empty " + cll.isEmpty( ));
          System.out.println(cll.removeHead( ));
          System.out.println(cll);
          System.out.println("empty " + cll.isEmpty( ));
class CLLNode{
     int data;
     CLLNode next;
     public CLLNode(int dta, CLLNode nxt){
          data = dta;
          next = nxt;
}

I'm not going thru all the code to just "fix it for you". But I do see one glaringly obvious mistake:
for(int i = 0; i < -999; i++)That says:
1) Initialize i to 0
2) while i is less than -999, do something
Since it is initially 0, it will never enter that loop body.

Help Implementing a queue as a circular linked list...

I have a set of code that I need to implement a circular linked list into, but I am not sure how to approach it at all. If anyone can point me to some pseudo code or sample code that I can modify for my use, that would be great.
I created a Class CircularQueue, which implements Queue, I just need to figure out how to write it.
Heres the code I have:
Queue Interface
public interface Queue<ElementType> {
     public void enqueue(ElementType e);
     public ElementType dequeue();
     public ElementType front();
     public boolean isEmpty();
Data Holder
public class DataHolder<ElementType> {
     // instance variables
     private ElementType _data;
      * Constructor for objects of class DataHolder
     public DataHolder() {
          _data = null;
     public void setContents(ElementType anItem) {
          _data = anItem;
     public ElementType getContents() {
         return _data;
DeqeueButton
import javax.swing.*;
import java.awt.event.*;
public class DequeueButton extends JButton {
    // instance variables
    private Queue<SmartRectangle> _queue;
    private QueuePanel _queuePanel;
     * Constructor for objects of class DequeueButton
    public DequeueButton(QueuePanel aQueuePanel) {
        super("Dequeue");
        _queuePanel = aQueuePanel;
        _queue = aQueuePanel.getQueue();
        this.addActionListener(new DequeueButtonListener());
    private class DequeueButtonListener implements ActionListener {
        private final int MOVE_LENGTH = 25;    // square size + 5
        public void actionPerformed(ActionEvent e) {
            _queue.dequeue();   // remove item from queue
            _queuePanel.repaint();
EnqueueButton
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class EnqueueButton extends JButton {
    // instance variables
    private Queue<SmartRectangle> _queue;
    private QueuePanel _queuePanel;
     * Constructor for objects of class EnqueueButton
    public EnqueueButton(QueuePanel aQueuePanel) {
        super("Enqueue");
        _queuePanel = aQueuePanel;
        _queue = _queuePanel.getQueue();
        this.addActionListener(new EnqueueButtonListener());
    private class EnqueueButtonListener implements ActionListener {
        private int _nextX, _nextY;
        private final int SQUARE_SIZE = 20;
        private final int MAX_X = 550;
        private final int MAX_Y = 350;
        private Color _currentColor;
        public EnqueueButtonListener() {
            _currentColor = Color.BLUE;
            _nextX = MAX_X;
            _nextY = MAX_Y;
        public void actionPerformed(ActionEvent e) {
            _queue.enqueue(new SmartRectangle(_nextX, _nextY, SQUARE_SIZE, SQUARE_SIZE, _currentColor, _queuePanel));
            this.changeColor();
            _nextX -= (SQUARE_SIZE+5); // location of next square in line
            if (_nextX < 0)     // if we reach edge of window, wrap
            {   _nextY -= (SQUARE_SIZE+5);
                _nextX = MAX_X;
            if (_nextY < 0)     // start over
                _nextY = MAX_Y;
            _queuePanel.repaint();
        public void changeColor() {
            if (_currentColor == Color.BLUE)
                _currentColor = Color.RED;
            else if (_currentColor == Color.RED)
                _currentColor = Color.GREEN;
            else if (_currentColor == Color.GREEN)
                _currentColor = Color.YELLOW;
            else if (_currentColor == Color.YELLOW)
                _currentColor = Color.BLACK;
            else if (_currentColor == Color.BLACK)
                _currentColor = Color.BLUE;
FrontButton
import javax.swing.*;
import java.awt.event.*;
public class FrontButton extends JButton {
    // instance variables
    private Queue<SmartRectangle> _queue;
    private QueuePanel _queuePanel;
     * Constructor for objects of class DequeueButton
    public FrontButton(QueuePanel aQueuePanel) {
        super("Front");
        _queuePanel = aQueuePanel;
        _queue = aQueuePanel.getQueue();
        this.addActionListener(new FrontButtonListener());
    private class FrontButtonListener implements ActionListener {
        public void actionPerformed(ActionEvent e) {
            SmartRectangle rectangle = _queue.front();    // remove item from queue
            SmartRectangle displayRect = _queuePanel.getDisplayFrontRect();
            if (rectangle != null)
                displayRect.setColor(rectangle.getColor());
            _queuePanel.repaint();
QueueApp
import javax.swing.*;
import java.awt.*;
public class QueueApp extends JFrame
     * Constructor for objects of class QueueApp
    public QueueApp(String title)
        super(title);
        this.setSize(600,450);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        QueuePanel queuePanel = new QueuePanel();
        javax.swing.JPanel buttonPanel = new JPanel(new FlowLayout());
        buttonPanel.add(new EnqueueButton(queuePanel));
        buttonPanel.add(new DequeueButton(queuePanel));
        buttonPanel.add(new FrontButton(queuePanel));
        this.add(queuePanel, BorderLayout.CENTER);
        this.add(buttonPanel, BorderLayout.SOUTH);
        this.setVisible(true);
    public static void main (String [] args)
        QueueApp app = new QueueApp("Queues at work: Object Oriented implementation.");
QueuePanel
import javax.swing.*;
import java.awt.*;
public class QueuePanel extends javax.swing.JPanel {
    // instance variables
    private Queue<SmartRectangle> _queue;
    private SmartRectangle _frontRect;
     * Constructor for objects of class QueuePanel
    public QueuePanel() {
        super();
        _queue = new CircularQueue<SmartRectangle>();
        _frontRect = new SmartRectangle(50,50,20,20,Color.WHITE, this);
   public Queue<SmartRectangle> getQueue() {
       return _queue;
   public SmartRectangle getDisplayFrontRect() {
       return _frontRect;
   public void paintComponent(Graphics aBrush) {
       super.paintComponent(aBrush);
       Graphics2D aBetterBrush = (Graphics2D) aBrush;
       Queue<SmartRectangle> tempQueue = new CircularQueue<SmartRectangle>();
       if (_frontRect.getColor() != this.getBackground())
           _frontRect.fill(aBetterBrush);
       while (!_queue.isEmpty()) {       // remove and display contents
           SmartRectangle rectangle = _queue.dequeue();
           rectangle.fill(aBetterBrush);
           tempQueue.enqueue(rectangle);
       while (!tempQueue.isEmpty()) {    // put contents back into _queue
           _queue.enqueue(tempQueue.dequeue());
       _frontRect.setColor(this.getBackground());
SmartNode
public abstract class SmartNode<ElementType> {
     public abstract boolean isEmpty();
     public abstract SmartNode<ElementType> dequeue(DataHolder<ElementType> aHolder);
     public abstract void front(DataHolder<ElementType> aHolder);
     public void enqueue(ElementType anItem){}
     public void setNext(SmartNode<ElementType> aNode) {
     } // override as needed
     public void setPrev(SmartNode<ElementType> aNode) {
     } // override as needed
SmartRectangle
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
public class SmartRectangle extends Rectangle2D.Double {
    // instance variables
    private JPanel _panel;
    private Color _color;
     * Constructor for objects of class SmartRectangle
    public SmartRectangle(int x, int y, int aWidth, int aHeight, Color aColor,
                          JPanel aPanel) {
        super(x, y, aWidth, aHeight);
        _panel = aPanel;
        _color = aColor;
    public void setLocation (int x, int y) {
        this.setFrame(x, y, this.getWidth(), this.getHeight());
    public Color getColor() {
        return _color;
    public void setColor(Color aColor) {
        _color = aColor;
    public void fill(Graphics2D aPaintBrush) {
        Color savedColor = aPaintBrush.getColor();
        aPaintBrush.setColor(_color);
        aPaintBrush.fill(this);
        aPaintBrush.setColor(savedColor);
}

> Yea I think I understand the concept of it, but I
dont know what the code is supposed to look like.
Showing you what the code is supposed to look like would be effectively giving you the answer, which kind of defeats the purpose of "extra credit". Have you tried anything so far? Post what you've got, and we can give you hints on how to work through it. I thought some of the descriptions here were very explicit hints, but if you need some additional guidance, let us know your specific questions (other than "show me the code").
Good luck!
~

Create a linked list

Hi guys!
I read the manual of java 2 and says that is not that pointers don't exist, they do exist but they are not explicit as they are in C languagge. So in need to create a circular linked list how can I do this? The instructions of the manual are not so clear. Does anyone have an idea and can give me a sample code?
Thanks to all
Maddy

References are like pointers except that you cannot make any add operation on them. But you can of course change their values to make it point to other objects.
This also means that you can create graph objects and every data structure you like. For example :
class BinaryNode {
    public Object data;
    public BinaryNode left;
    public BinaryNode right;
}To create binary trees or
class GraphNode {
    public Object data;
    public ArrayList links;
}Where links is a Java list containing a list of links (references) to other GraphNode.
Matthieu

Circular Double Linked List

If the circular double linked list has only one item, will that item's next/previous node references point to itself?

Yeah, it would make sense. But I'm wondering if there's any standard?
It could also make sense for the references to simply be null.

Saving Linked List to file

Hello,
I have a simple linked link. How do I save the entire list into a file, and and how to I restore the entire link list back into the program so that I can use it normally again?
I guess Serialization is used?
I don't want to save save all the filds in a file, then "re create" the link list by loops etc.

Since Serialization saves the object in question and all the objects it references, if you make you're liunked list element Serializable and then save the first element, the Serialization process will save the entire list.
To get it back, read an Object from the file, it will be the first element of your list and its next link will point at the next element, etc.
If you have a circular list, this still works since the Serialization process will recognice that your saving the same object a second time and only send a reference.

HELLLP with LInked List

hello Java World,
Have a few questions regarding linked lists:
1) are they already implemented in java or are they just currently an interface/abstract class?
2) Jus to make sure: The linkedlist interface/class implement the List Interface(which is in the hierachy of collections)
3)What are Node objects? (ie. Node head=new Integer(5);)
Do they have anything to do with pointers?
4) Are the various kinds of linked lists(circularly,doubly,singly) already implemented?(This is related to question 1)
Thank you in advance
RahimS

[snip]
4. In general, yup. In java, I think you've only got
the singly linked listSince the LinkedList class implements the List interface, it behaves like any other List, in that you can traverse the thing in order or access its elements randomly. I am not sure I understand the OP's original question, but the API docs do say:
" All of the operations perform as could be expected for a doubly-linked list. "
for what that's worth
Lee

After Delete in Linked list...unable to display the linked list

Hi...i know that there is an implementation of the class Linked Link but i am required to show how the linked list works in this case for my project...please help...
Yes..I tried to delete some objects in a linked list but after that i am not able to display the objects that were already in the linked list properly and instead it throws an NullPointerException.
Below shows the relevant coding for deleting and listing the linked list...
public Node remove(Comparator comparer) throws Exception {
     boolean found = false;
     Node prevnode = head;          //the node before the nextnode
     Node deletedNode = null;     //node deleted...
     //get next node and apply removal criteria
     for(Node nextnode = head.getNextNode(); nextnode != null; nextnode = nextnode.getNextNode()) {
          if(comparer.equals(nextnode)) {
               found = true;
               //remove the next node from the list and return it
               prevnode.setNextNode(nextnode.getNextNode());
               nextnode.setNextNode(null);
               deletedNode = nextnode;
               count = count - 1;
               break;
     if (found) return deletedNode;
     else throw new Exception ("Not found !!!");
public Object[] list() {
     //code to gather information into object array
     Node node;
     Object[] nodes = new Object[count];
     node = head.getNextNode();
     for (int i=0; i<count; i++) {
          nodes[i] = node.getInformation(); // this is the line that cause runtime error after deleting...but before deleting, it works without problem.
          node = node.getNextNode();
     return nodes;
}Please help me in figuring out what went wrong with that line...so far i really can't see any problem with it but it still throws a NullPointerException
Thanks

OK -- I've had a cup and my systems are coming back on line...
The problem looks to be the way that you are handling the pointer to the previous node in your deletion code. Essentially, that is not getting incremented along with the nextNode -- it is always pointing to head. So when you find the node to delete then the line
   prevnode.setNextNode(nextnode.getNextNode());will set the nextNode for head to be null in certain situations (like if you are removing the tail, for instance).
Then when you try to print out the list, the first call you make is
node = head.getNextNode();Which has been set to null, so you get an NPE when you try to access the information.
Nothing like my favorite alkaloid to help things along on a Monday morning...
- N

Problem with Queue and linked list

Hi... i've got an assignment it start like this.
You are required to write a complete console program in java includin main() to demonstrate the following:
Data Structure: Queue, Priority Queue
Object Involved: Linked-List, PrintJob
Operations Involved:
1. insert
2. remove
3. reset
4. search
Dats all... I've been given this much information... Can any1 try to help me please... How to make a start??? And wat does the print job means???
Can any1 tell me wat am supposed to do...

Hi,
Why don't you start your demo like this?
import java.io.IOException;
public class Demo {
     public Demo() {
     public void startDemo() throws IOException {
          do {
               System.out.println("String Console Demo ");
               System.out.println("\t" + "1. Queue Demo");
               System.out.println("\t" + "2. PriorityQueue Demo");
               System.out.println("\t" + "3. LinkedList Demo");
               System.out.println("\t" + "4. PrintJob Demo");
               System.out.println("Please choose one option");
               choice = (char) System.in.read();
               showDemo(choice);
          } while (choice < '1' || choice > '4');
     public void showDemo(char ch) {
          switch (ch) {
          case '1':
               System.out.println("You have chosen Queue Demo ");
               showOperations();
               break;
          case '2':
               System.out.println("You have chosen Priority Queue Demo ");
               showOperations();
               break;
          case '3':
               System.out.println("You have chosen LinkedList Demo ");
               showOperations();
               break;
          case '4':
               System.out.println("You have chosen Print Job Demo ");
               showOperations();
               break;
     private void showOperations() {
          System.out.println("Please choose any operations ");
          System.out.println("\t" + "1. Insert ");
          System.out.println("\t" + "2. Remove ");
          System.out.println("\t" + "3. Reset ");
          System.out.println("\t" + "4. search ");
     public static void main(String[] args) throws IOException {
          Demo demo = new Demo();
          demo.startDemo();
     private char choice;
Write a separate classes for the data structures show the initial elements and call the methods based on the operations then show the result.
Thanks

How to use methods when objects stored in a linked list?

Hi friend:
I stored a series of objects of certain class inside a linked list. When I get one of them out of the list, I want to use the instance method associated with this object. However, the complier only allow me to treat this object as general object, ( of Object Class), as a result I can't use instance methods which are associated with this object. Can someone tell me how to use the methods associated with the objects which are stored inside a linked list?
Here is my code:
import java.util.*;
public class QueueW
     LinkedList qList;
     public QueueW(Collection s) //Constructor of QuequW Class
          qList = new LinkedList(s); //Declare an object linked list
     public void addWaiting(WaitingList w)
     boolean result = qList.isEmpty(); //true if list contains no elements
          if (result)
          qList.addFirst(w);
          else
          qList.add(w);
     public int printCid()
     Object d = qList.getFirst(); // the complier doesn't allow me to treat d as a object of waitingList class
          int n = d.getCid(); // so I use "Object d"
     return n; // yet object can't use getCid() method, so I got error in "int n = d.getCid()"
     public void removeWaiting(WaitingList w)
     qList.removeFirst();
class WaitingList
int cusmNo;
String cusmName;
int cid;
private static int id_count = 0;
     /* constructor */
     public WaitingList(int c, String cN)
     cusmNo = c;
     cusmName = cN;
     cid = ++id_count;
     public int getCid() //this is the method I want to use
     return cid;

Use casting. In other words, cat the object taken from the collection to the correct type and call your method.
   HashMap map = /* ... */;
   map.put(someKey, myObject);
   ((MyClass)(map.get(someKey)).myMethod();Chuck

Can I import my old link lists into 365 site?

Hi I would like to import all my hard work from my old 2010 sharepoint site into the new 365 site.
I exported my links to excel but I cannot see an import option on a link list in 365.
Surely there must be an easy way to do this that I am missing?
thanks

Below are the steps to save List as Template:
>> Go to the List - List Settings - Click on Save List as Template - Provide Template Name and make sure you check the "With Content" box available on the page.
Once the List is successfully saved as template, you will find the template under List Templates gallery. Download that template it should have ".stp" extension. Get that file and upload the file to List Templates gallery of your SharePoint Online Office
365 site. Then create a new app and there you should find the Template and create a list using that template.
If you have any questions then let me know.
Please ensure that you mark a question as Answered once you receive a satisfactory response.

Is there a way to create a "Horizontal Links List" from a query?

Hi,
Is there a way to create a "Horizontal Links List" from a query?
I want to display file names that I have uploaded as links to a display page.
I don't know how to create my own template yet as I've read... I saw Jes had posted this idea...
Thanks, Bill

Yes, that is great Chris!
Thanks for the site....
Once I dynamically create the HTML for the list how do I feed it into the page?
as an item? Can I access an HTML region body dynamically?
Thanks, Bill

Circular Linked List

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