Building a linked list

Hi, Im having some trouble and was wondering if anyone could figure this out. I need to read in integers to build a linked list, but stuck on what to do after I read in a integer. Any help would be much appreciated!
class lp
    public int first;
    public lp next;
    public lp(int first1, lp next1)
      first = first1; //first item in list
      next = next1; //next item in list
public static void main(String[] args)
    int n = 0;
    Scanner sc = new Scanner(System.in);
    while(n!=-1)
    System.out.println("input: ");
    n = sc.nextInt();
    lp l = new lp(n,null); //I tried this but I get a error nonstatic variable this cannot be ref from a static context
}Edited by: jennahogan1 on Aug 14, 2008 6:15 AM

jennahogan1 wrote:
A linked list is a series of nodes with an item(int, string, double, etc) and a reference to the next node in the listRight, it is a data structure as you described. Next question (which has already been asked), "Are you trying to create your own data structure or are you allowed to use Java's?"

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In my C++ course, we are on a chapter about linked lists, and the professor has given us a template to make the linked lists work. It comes in three files (a header, a source file, and a main source file). I've made some adjustments -- the original files the professor provided brought up 36 errors and a handful of warnings, but I altered the #include directives and got it down to 2 errors. The problematic part of the code (the part that contains the two errors) is in one of the function definitions, print_list(), in the source file. That function definition is shown below, and I've marked the two statements that have the errors using comments that say exactly what the errors say in my Xcode window under those two statements. If you want to see the entire template, I've pasted the full code from all three files at the bottom of this post, but for now, here is the function definition (in the source file) that contains the part of the code with the errors:
void LinkedList::printlist( )
// good for only a few nodes in a list
if(isEmpty() == 1)
cout << "No nodes to display" << endl;
return;
for(CURSOR = FRONT_ptr; CURSOR; CURSOR = CURSOR-> link)
{ cout << setw(8) << CURSOR->name; } cout << endl; // error: 'setw' was not declared in this scope
for(CURSOR = FRONT_ptr; CURSOR; CURSOR = CURSOR-> link)
{ cout << setw(8) << CURSOR->test_grade; } cout << endl; // error: 'setw' was not declared in this scope
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For reference, here is the full code from all three files that make up the template:
linkedlist.h (header file):
#ifndef LINKED_LINKED_H
#define LINKED_LINKED_H
struct NODE
string name;
int test_grade;
NODE * link;
class Linked_List
public:
Linked_List();
void insert(string n, int score);
void remove(string target);
void print_list();
private:
bool isEmpty();
NODE *FRONT_ptr, *REAR_ptr, *CURSOR, *INSERT, *PREVIOUS_ptr;
#endif
linkedlist.cpp (source file):
#include <iostream>
using namespace std;
#include "linkedlist.h"
LinkedList::LinkedList()
FRONT_ptr = NULL;
REAR_ptr = NULL;
PREVIOUS_ptr = NULL;
CURSOR = NULL;
void Linked_List::insert(string n, int score)
INSERT = new NODE;
if(isEmpty()) // first item in List
// collect information into INSERT NODE
INSERT-> name = n;
// must use strcpy to assign strings
INSERT -> test_grade = score;
INSERT -> link = NULL;
FRONT_ptr = INSERT;
REAR_ptr = INSERT;
else // else what?? When would this happen??
// collect information into INSERT NODE
INSERT-> name = n; // must use strcpy to assign strings
INSERT -> test_grade = score;
REAR_ptr -> link = INSERT;
INSERT -> link = NULL;
REAR_ptr = INSERT;
void LinkedList::printlist( )
// good for only a few nodes in a list
if(isEmpty() == 1)
cout << "No nodes to display" << endl;
return;
for(CURSOR = FRONT_ptr; CURSOR; CURSOR = CURSOR-> link)
{ cout << setw(8) << CURSOR->name; } cout << endl; // error: 'setw' was not declared in this scope
for(CURSOR = FRONT_ptr; CURSOR; CURSOR = CURSOR-> link)
{ cout << setw(8) << CURSOR->test_grade; } cout << endl; // error: 'setw' was not declared in this scope
void Linked_List::remove(string target)
// 3 possible places that NODES can be removed from in the Linked List
// FRONT
// MIDDLE
// REAR
// all 3 condition need to be covered and coded
// use Trasversing to find TARGET
PREVIOUS_ptr = NULL;
for(CURSOR = FRONT_ptr; CURSOR; CURSOR = CURSOR-> link)
if(CURSOR->name == target) // match
{ break; } // function will still continue, CURSOR will
// mark NODE to be removed
else
{ PREVIOUS_ptr = CURSOR; } // PREVIOUS marks what NODE CURSOR is marking
// JUST before CURSOR is about to move to the next NODE
if(CURSOR == NULL) // never found a match
{ return; }
else
// check each condition FRONT, REAR and MIDDLE
if(CURSOR == FRONT_ptr)
// TARGET node was the first in the list
FRONT_ptr = FRONT_ptr -> link; // moves FRONT_ptr up one node
delete CURSOR; // deletes and return NODE back to free memory!!!
return;
}// why no need for PREVIOUS??
else if (CURSOR == REAR_ptr) // TARGET node was the last in the list
{ // will need PREVIOUS for this one
PREVIOUS_ptr -> link = NULL; // since this node will become the last in the list
REAR_ptr = PREVIOUS_ptr; // = REAR_ptr; // moves REAR_ptr into correct position in list
delete CURSOR; // deletes and return NODE back to free memory!!!
return;
else // TARGET node was the middle of the list
{ // will need PREVIOUS also for this one
PREVIOUS_ptr -> link = CURSOR-> link; // moves PREV nodes' link to point where CURSOR nodes' points
delete CURSOR; // deletes and return NODE back to free memory!!!
return;
bool Linked_List::isEmpty()
if ((FRONT_ptr == NULL) && (REAR_ptr == NULL))
{ return true; }
else
{ return false;}
llmain.cpp (main source file):
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
#include "linkedlist.h"
int main()
Linked_List one;
one.insert("Angela", 261);
one.insert("Jack", 20);
one.insert("Peter", 120);
one.insert("Chris", 270);
one.print_list();
one.remove("Jack");
one.print_list();
one.remove("Angela");
one.print_list();
one.remove("Chris");
one.print_list();
return 0;

setw is the equivalent of the field width value in printf. In your code, the printf version would look like:
printf("%8s", CURSOR->name.c_str());
I much prefer printf over any I/O formatting in C++. See the printf man page for more information. I recommend using Bwana: http://www.bruji.com/bwana/
I do think it is a good idea to verify your code on the platform it will be tested against. That means Visual Studio. However, you don't want to use Visual Studio. As you have found out, it gets people into too many bad habits. Linux is much the same way. Both development platforms are designed to build anything, whether or not it is syntactically correct. Both GNU and Microsoft have a long history of changing the language standards just to suit themselves.
I don't know what level you are in the class, but I have a few tips for you. I'll phrase them so that they answers are a good exercise for the student
* Look into const-correctness.
* You don't need to compare a bool to 1. You can just use bool. Plus, any integer or pointer type has an implicit cast to bool.
* Don't reuse your CURSOR pointer as a temporary index. Create a new pointer inside the for loop.
* In C++, a struct is the same thing as a class, with all of its members public by default. You can create constructors and member functions in a struct.
* Optimize your function arguments. Pass by const reference instead of by copy. You will need to use pass by copy at a later date, but don't worry about that now.
* Look into initializer lists.
* In C++ NULL and 0 are always the same.
* Return the result of an expression instead of true or false. Technically this isn't officially Return Value Optimization, but it is a good habit.
Of course, get it running first, then make it fancy.

Remove element in linked list linked list

here's my codes
public class Student
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public class LinkedList extends java.util.LinkedList
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        firstNode = lastNode = currNode = null;
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        else
            firstNode = new ListNode(insertItem, firstNode);
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        else
            lastNode = lastNode.next = new ListNode(insertItem);
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        removeItem = lastNode.data;
        if (firstNode.equals(lastNode))
            firstNode = lastNode = null;
        else {
            ListNode current = firstNode;
            while (current.next != null)
                current = current.next;
            lastNode = current;
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    { return firstNode == null;}
    public synchronized Object getFirst() {
        if (isEmpty())
            return null;
           else {
                currNode = firstNode;
                return currNode.data;
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        if (currNode != lastNode) {
            currNode = currNode.next;
            return currNode.data;
        else
            return null;
    public synchronized String print() {
        String out = "";
        if (isEmpty()) {
            out = "Empty "+ name;
        out = "The "+ name+ " is:\n";
        ListNode current = firstNode;
        while (current != null) {
            out += ""+ current.data.toString();
            current = current.next;
        return out;
    public synchronized Object getLast() {
        if (isEmpty())
            return null;
        else {
            currNode = lastNode;
            return currNode.data;
}// end LinkedListand the application class
import java.io.*;
import java.util.*;
import javax.swing.*;
public class StudentAppLL
    public static void main(String[] args) throws IOException {
        LinkedList std = new LinkedList();
        BufferedReader br = new BufferedReader(new FileReader("studentIn.txt"));
        PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("studentOut.txt")));
        String line = br.readLine();
        while (line != null) {
            StringTokenizer tk = new StringTokenizer(line);
            while (tk.hasMoreTokens()) {
                String n = tk.nextToken();
                String m = tk.nextToken();
                Student a = new Student(n, m);
                std.insertAtFront(a);
                line = br.readLine();
        std.print();
        System.out.print(std.getFirst());
        Student data = (Student)std.getFirst();
        String matric;
        String nm = "Zaki";
        while (data != null) {
            if (data.getName().equalsIgnoreCase(nm)) {
                System.out.print(data.getName()+ " ada\n");
                //std.re
                data = (Student)std.getNext();
        Student b = new Student("Umar","2004163943");
        std.insertAtBack(b);
        String name = "", matric = "", s = "";
        boolean stop = false;
        int size = std.size();
        JOptionPane.showMessageDialog(null, size);
        s = JOptionPane.showInputDialog("A: Add Student\nR: Remove Student" +
                                       "\nV: View Sorted Student List\nS: Stop ");
        while(!stop){
            if (s.equalsIgnoreCase("A")){
                name = JOptionPane.showInputDialog("Enter student name: ");
                matric = JOptionPane.showInputDialog("Matric number: ");
                Student student = new Student(name, matric);
                std.insertAtBack(student);
                s = JOptionPane.showInputDialog("A: Add Student\nR: Remove Student" +
                                       "\nV: View Sorted Student List\nS: Stop ");
            else if (s.equalsIgnoreCase("R")){
                Student data = (Student)std.getFirst();
                Student first = (Student)std.getFirst();
                Student last = (Student)std.getLast();
                JOptionPane.showMessageDialog(null, "First: "+ first+ "\nLast: "+ last);
                String ns = JOptionPane.showInputDialog("Enter the student's name");
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                    // buang kalau pd bhgn dpn
                    if (data.getName().equalsIgnoreCase(ns) && ns.equalsIgnoreCase(first.getName())) {
                        JOptionPane.showMessageDialog(null, first.getName());
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                        //std.removeFromFront();
                        std.remove(data);
                        s = JOptionPane.showInputDialog("A: Add Student\nR: Remove Student" +
                                       "\nV: View Sorted Student List\nS: Stop ");
                     if (data.getName().equalsIgnoreCase(ns) && ns.equalsIgnoreCase(last.getName())) {
                        std.removeFromBack();
                        JOptionPane.showMessageDialog(null, data.getName()+ " kena buang");
                         s = JOptionPane.showInputDialog("A: Add Student\nR: Remove Student" +
                                       "\nV: View Sorted Student List\nS: Stop ");
                     data = (Student)std.getNext();
                }// habis while loop
            // keluar jika pilih 's'
            else if (s.equalsIgnoreCase("S")){ stop = true;}
            else { JOptionPane.showMessageDialog(null, "Wrong input"); }
        JOptionPane.showMessageDialog(null, std.print());
        br.close();
        pw.close();
    }// end main class
}and here's the studentIn.txt data
Ahmad 2004199877
Hanif 2005378219
Zaki 2004456790
how can i do it? i mean to remove other than first element?
Message was edited by:
ikki_72

> public class LinkedList extends java.util.LinkedList
// instance variables - replace the example below with your own
private ListNode firstNode;
private ListNode lastNode;
private ListNode currNode;
private String name;
[ ... ]Eeeeeeeeeew! Don't do that ever again! A java.util.LinkedList is very
well capable of managing a linked list (it is a linked list after all).
Either build your own linked list mechanics or use a LinkedList as
one of the member variables of your class, but please don't do this.
kind regards,
Jos ( ... that was scary ... )

Linked Lists

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Sorry, after rereading your initial post a third time, I see there is more to what you are asking and displaying than is easily discernable.
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null

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Thanks in Advance.
Message was edited by:
Vertix
Message was edited by:
Vertix
Message was edited by:
Vertix
Message was edited by:
Vertix
Message was edited by:
Vertix

Well, I tried to remove Node b, and just use the Node
m to set up my LinkedList.[ code snipped ]
But it's giving NullPointerExceptions everytime I try to run it. I already
created a Node m at the begging, so I don't see where it's getting the
nullpointer.That's not how you should create that list. You need a new node per
element in the rdata[] array. There are two possible states:
1) there isn't a list yet, i.e. the 'root' element equals null
2) there's a list already and 'm' points to the last element of the list.
This is how you do it:m= root; // both are null; see 1)
for (int i= 0; i < rdata.length; i++) { // build the list
   Node b= new Node(); // build a new node
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if (root == null) // first list element?
root= b;
else // no, hookup to last element
m.left= b;
m= b; // m points to last element
kind regards,
Jos

*** glibc detected *** corrupted double-linked list: 0x004ec848 ***

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I have an issue with Report Builder and linking to a report.
I have a Matrix report with two Row Groups of Area and Sub Area. It simply shows a total by area and subarea of our property stock.
I have a detail report that I want to link to. I want the matrix to work that when you click on either the area or the sub area it shows you those properties on a separate report.
On my detail report I have created two parameters. One called area_parameter and one called subarea_parameter. These are then added to the filter od the dataset.
On the matrix report – on the subarea total - I have an action to open the detail report when area_parameter = Area and subarea_parameter = subarea. That works perfectly.
The issue I have when I add an action to area. I have just placed area_parameter = Area in the action and I keep getting an error –
The ‘subarea_parameter’ parameter is missing a value.
What do I need to do to get this to work. As I’m only clicking on the Area, the Sub Area shouldn’t matter?
I’m lost at how to get this to work. Is there a way round this.
Both report have the same shared dataset

Hi ikilledbill,
According to your description, there is a matrix with two row groups: Area and Sub Area. You want to jump to detail report when you click either the area or the sub area. It works fine when you click sub area, but when you add Go to report action to area,
the error occurred.
When we click area, we could not pass values of sub area to detail report by design. As a workaround, we can set default values for subarea parameter. For detail information, please refer to the following steps:
Create a dataset for subarea parameter.
Right-click subarea parameter and open Parameter Properties dialog box.
Type name and prompt, select Allow multiple values check box.
Click Default Values in left pane, select Get values from the query, then select dataset and value field from drop down list, then click OK.
Right-click area and click Text Box Properties.
Click Action in left pane, select Go to report and select a subreport from drop down list.
Click Add button to add parameter to run the detail report.
The following screenshot is for your reference:
If you have any more questions, please feel free to ask.
Thanks,
Wendy Fu
Wendy Fu
TechNet Community Support

Strange error message - linked lists (again)

I have to keep at this linked list thing if I'm ever going to really understand it!!
I have created a method to create a linked list via user input. I'm receiving only one strange ERROR, which states:
"This method must return a result of of type ListADT.Node."
And I have just started building my class ListADT...
class ListADT{
public Node createList(int aNumber){     // THIS IS WHERE THE ERROR POINTS
      * integer variable aNumber is the length of the list user wishes to create.
     Scanner console = new Scanner(System.in);
     int number;                    // declare variable number as an integer.
     Node newNode = new Node();          // declare and initialize newNode.
     Node first = new Node();          // declare and initialize first.
     Node last = new Node();               // delcare and initizlize last.
     try
          for(int i = 0; i <= aNumber; i++){               // for loop to enter numbers to build list.
          System.out.println("Please enter an integer: ");     // prompt user.
          number = console.nextInt();                    // assign user input to variable number.
          newNode.info = number;          // assign number to newNode;
          if(first == null){               // checks to see if Node first is a null value.
               first = newNode;          // if true, then this node is the first and last node in the list.
               last = newNode;
          else{                              // if first is not null, then newNode is placed at the end of the list.
               last.link = newNode;
               last = newNode;
          return first;
     catch (InputMismatchException imeRef)     //Catches non-integer values
          System.out.println("You entered a non-Integer! " + imeRef.toString());     //Prints error message

Now why can't the error messages help
out a little more? I would have never guessed that
there was a problem with the catch block not
returning anything!!The message was pretty informative -- it told you what was wrong. If the compiler could be so smart as to be able to tell you exactly what to fix, then the compiler would be able to write code all by itself -- and then you'd be out of a job.

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

Building a linked list

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