A queue using a linked list..having troubles with the rest

Question

ok...
this is the assignment ( [http://jessehardesty.com/uploads/p2.JPG] ) picture is kind of big...
I have to have a "queue" class, but I will have to remove some people from the line that are in the middle (which is why i put it in quotes).
this is the queue class I have as of now...
public class Queue
       private static class Node
          int item;
          Node next;
       private Node head = null;  // Points to first Node in the queue.
                                  // The queue is empty when head is null.
       private Node tail = null;  // Points to last Node in the queue.
       void enqueue( int N ) {
             // Add N to the back of the queue.
          Node newTail = new Node();  // A Node to hold the new item.
          newTail.item = N;
          if (head == null) {
                // The queue was empty.  The new Node becomes
                // the only node in the list.  Since it is both
                // the first and last node, both head and tail
                // point to it.
             head = newTail;
             tail = newTail;
          else {
                // The new node becomes the new tail of the list.
                // (The head of the list is unaffected.)
             tail.next = newTail;
             tail = newTail;
       int dequeue() {
              // Remove and return the front item in the queue.
              // Note that this can throw a NullPointerException.
          int firstItem = head.item;
          head = head.next;  // The previous second item is now first.
          if (head == null) {
                // The queue has become empty.  The Node that was
                // deleted was the tail as well as the head of the
                // list, so now there is no tail.  (Actually, the
                // class would work fine without this step.)
             tail = null;
          return firstItem;
       boolean isEmpty() {
              // Return true if the queue is empty.
          return (head == null);
    }my problem is that I don't know how to go about doing the units of time. We are given a data file with the time of arrival, length of transaction, amt bought, and money spent.
it's kind of long or I'd post it...but they are all ints. I'll have to read from the file. My problem (for now) is that I don't know what kind of loop to do, and how to read them in correctly...it is 4 ints per line in the file, spaces in between of course. What kind of loop should be used?...and how do I go about keeping track of all the "people" in line without using 40+ counters (one for each "person").
thanks, and hopefully that makes some sense.
Edited by: Taco_John on Mar 23, 2008 5:08 PM

Answer 1

* Queue.java
* Created on March 24, 2008, 3:12 PM
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
package test;
import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;
* @author Rajesh
public class Queue <T>
private static class Node<T>
int item;
int custArrive;
int transTime;
int amtBought;
int dollSpent;
Node next;
private Node head, tail;
private int count;
public Queue()
count = 0;
head = tail = null;
public void enqueue( T element ,int a,int b,int c,int d) {
// Add N to the back of the queue.
Node<T> newTail = new Node<T>(); // A Node to hold the new item.
if (head == null)
head = newTail;
head.custArrive = a;
head.transTime = b;
head.amtBought = c;
head.dollSpent = d; tail = newTail;
else
tail.next = newTail;
tail = newTail;
tail.custArrive = a;
tail.transTime = b;
tail.amtBought = c;
tail.dollSpent = d;
private int dequeue()
int firstItem = head.item;
head = head.next; // The previous second item is now first.
if (head == null)
tail = null;
return firstItem;
public void showElement()
Node<T> newTail = new Node<T>();
for(newTail=head; ;newTail=newTail.next)
System.out.println(""+newTail.custArrive+"\t"+newTail.transTime+"\t"+newTail.amtBought+"\t"+newTail.dollSpent);
if(newTail == tail)
break;
*}* boolean isEmpty()
// Return true if the queue is empty.
return (head == null);
public static void main (String [] args)throws IOException
int custArrive;
int transTime;
int amtBought;
int moneySpent;
FileReader infile = new FileReader ("C:/Documents and Settings/pb46627/Desktop/prog3.txt");
Scanner fin = new Scanner (infile);
Queue myQueue = new Queue();
int i=0;
while (fin.hasNextInt())
custArrive = fin.nextInt();
transTime = fin.nextInt();
amtBought = fin.nextInt();
moneySpent = fin.nextInt();
myQueue.enqueue(i++,custArrive,transTime,amtBought,moneySpent);
*//fin.next();*
i++;
myQueue.showElement();
*// System.out.println(""+myQueue.count);*
And this is the Input file i used.......
10     20     30     40
50     60     70      80
90     100     110     120
prog3.txt
Now you can able to see the output as
10     20     30     40
50     60     70      80
90     100     110     120
i use BOLD FONT_ , indicates my changes
just try with this and comment.......
i'm waiting for your reply.....
thank you
rajesh