Need help accessing data in LinkedList

[Clerek]

I am having trouble figuring out how to access the data that is stored inside a LinkedList. I have set the LinkedList to contain objects of type Box and Letter. These two classes extend to the super class Package. The Box constructor is made up of tracking number, weight, length, width, and height. The letter constructor is made up of tracking number, weight, length and width. What I need to do is make a getter to access all the things that make up the Box and Letter objects that i can access inside another class Truck. The whole purpose of this is to simulate the activities of a delivery truck transporting packages from one city to another. Please note that the load method in the Truck class is incomplete because I don't know how to access the data within the LinkedList. Below is the code. This is for an assignment that is VERY late so help is much appreciated...

LinkedList class

@SuppressWarnings({ "rawtypes" })

public class LinkedList
{
   protected static class Node
   {
      protected Comparable data;
      protected Node next;

      protected Node ( Comparable data )
      {
         this.data = data;
         this.next = null;
      }// end constructor

      protected Node ( Comparable data, Node next )
      {
         this.data = data;
         this.next = next;
      }// end constructor

      public void setData ( Comparable data )
      {  
			this.data = data;
		}// end setData

      public void setNext ( Node next )
      { 
			this.next = next;
		}// end setNext

      public Comparable getData ()
      {
			return this.data;
		}// end getData

      public Node getNext ()
      {
			return this.next;
		}// end getNext
      
		
   }// end Node class

   protected Node head = null;
   
   public void add(Comparable string)
   {
	   Node newNode = new Node(string);
	   if (size == 0)
	   {
		   head = newNode;
	   }
	   else
	   {
		   Node curr = head;
		   while (curr.next != null)
		   {
			   curr = curr.next;
		   }
		   curr.next = newNode;
	   }
	   size++;
   }
}// end LinkedList class

Package, Box, and Letter classes

public class Package implements Comparable <Package>
{
	String tracking, weight;
	
	public Package(String tracking, String weight)
	{
		this.tracking = tracking;
		this.weight = weight;
	}
	
	public int getTracking() {
		return Integer.parseInt(tracking);
	}

	public int getWeight() {
		return Integer.parseInt(weight);
	}

	@Override
	public int compareTo(Package arg0) 
	{
		// TODO Auto-generated method stub
		return 0;
	}
}


public class Letter extends Package
{
	private String length, width, type;
	
	public Letter(String tracking, String weight, String length, String width)
	{
		super(tracking, weight);
		this.length = length;
		this.width = width;
		this.type = "Letter";
	}

}


public class Box extends Package 
{
	private String length, width, height, type;

	public Box(String tracking, String weight, String length, String width, String height) 
	{
		super(tracking, weight);
		this.length = length;
		this.width = width;
		this.height = height;
		this.type = "Box";
	}

}

And finally the Truck class

//Try making the truck constructor just put it into a LinkedList and then when calling load method in truck class, try to load first and then cast the type

import java.io.*;
import java.util.Scanner;

public class Truck
{
	String driver;
	int maxPackages, boxWeight, letterWeight;
	LinkedList packs = new LinkedList();
	LinkedList loaded = new LinkedList();
	Scanner fin;
	
	public Truck(String string)
	{
		try{
			fin = new Scanner(new File(string));
			if(fin.hasNextLine())
			{
				this.driver = fin.nextLine();
				this.maxPackages = fin.nextInt();
				//fin.nextLine();
			}
			while(fin.hasNextLine())
			{
				String tracking = fin.next();
				fin.nextLine();
				if(tracking.endsWith("0"))
				{
					//String tracking = fin.toString();
					String weight = fin.nextLine();
					String length = fin.nextLine();
					String width = fin.nextLine();
					Package n = new Letter(tracking, weight, length, width);
					packs.add(n);
				}
				else if(tracking.endsWith("1"))
				{
					//String tracking = fin.nextLine();
					String weight = fin.nextLine();
					String length = fin.nextLine();
					String width = fin.nextLine();
					String height = fin.nextLine();
					Package m = new Box(tracking, weight, length, width, height);
					packs.add(m);
				}
				//packs.add(fin.nextLine());
			}
		}catch(IOException io){
			io.printStackTrace();
		}
	}
	
	public void load() 
	{
		//System.out.println(packs.head.getData());
		LinkedList temp = packs;
		while(temp.head.data != null)
		{
			if(temp.head.)
			{
				//temp.head.data;
				temp.head = temp.head.next;
			}
			else if(temp.head.getData().toString().contains("Box"))
			{
				System.out.println("Box");
				temp.head = temp.head.next;
			}
		}
		
		
		
	}

 
	
}// end Truck class

[Norm]

How do you execute the code for testing? I don't see a main method.

[Clerek]

Thanks for the response! Main is just a simple tester that instantiates a truck object:

public static void main(String [] args)
{
       Truck theTruck = new Truck("manifest.txt");
       theTruck.load();
       theTruck.drive(); //doesn't really do anything...
       theTruck.unload();
}//end main

[Norm]

I get several compiler errors. Can you fix them so the code will execute?

[Clerek]

Please note that the load method doesn't work...

Truck class

import java.io.*;
import java.util.Scanner;

public class Truck
{
	String driver;
	int maxPackages, boxWeight, letterWeight;
	LinkedList packs = new LinkedList();
	LinkedList loaded = new LinkedList();
	Scanner fin;
	
	public Truck(String string)
	{
		try{
			fin = new Scanner(new File(string));
			if(fin.hasNextLine())
			{
				this.driver = fin.nextLine();
				this.maxPackages = fin.nextInt();
				//fin.nextLine();
			}
			while(fin.hasNextLine())
			{
				String tracking = fin.next();
				fin.nextLine();
				if(tracking.endsWith("0"))
				{
					//String tracking = fin.toString();
					String weight = fin.nextLine();
					String length = fin.nextLine();
					String width = fin.nextLine();
					Package n = new Letter(tracking, weight, length, width);
					packs.add(n);
				}
				else if(tracking.endsWith("1"))
				{
					//String tracking = fin.nextLine();
					String weight = fin.nextLine();
					String length = fin.nextLine();
					String width = fin.nextLine();
					String height = fin.nextLine();
					Package m = new Box(tracking, weight, length, width, height);
					packs.add(m);
				}
				//packs.add(fin.nextLine());
			}
		}catch(IOException io){
			io.printStackTrace();
		}
	}
	
	public void load() 
	{
		//System.out.println(packs.head.getData());
		LinkedList temp = packs;
		while(temp.head.data != null)
		{
			if(temp.head.)
			{
				//temp.head.data;
				temp.head = temp.head.next;
			}
			else if(temp.head.getData().toString().contains("Box"))
			{
				System.out.println("Box");
				temp.head = temp.head.next;
			}
		}
		
		
		
	}

 
	
}// end Truck class

Main

public class TruckTester 
{

	/**
	 * @param args
	 */
	public static void main(String[] args) 
	{
		Truck theTruck = new Truck("manifest.txt");
		theTruck.load();
		//theTruck.drive();
		//theTruck.unload();

	}// end main method

}// end TruckTester class

LinkedList

@SuppressWarnings({ "rawtypes" })

public class LinkedList
{
   protected static class Node
   {
      protected Comparable data;
      protected Node next;

      protected Node ( Comparable data )
      {
         this.data = data;
         this.next = null;
      }// end constructor

      protected Node ( Comparable data, Node next )
      {
         this.data = data;
         this.next = next;
      }// end constructor

      public void setData ( Comparable data )
      {  
			this.data = data;
		}// end setData

      public void setNext ( Node next )
      { 
			this.next = next;
		}// end setNext

      public Comparable getData ()
      {
			return this.data;
		}// end getData

      public Node getNext ()
      {
			return this.next;
		}// end getNext
      
		
   }// end Node class

   protected Node head = null;
   protected int  size = 0;

   // Return the present size of the linked list
   
   public int size()
   {
	   return size;
   }// end size

   public void addFirst(Comparable s)
   {
	   Node newNode = new Node(s, head);
	   head = newNode;
	   size++;
   }

   public void addLast(Comparable node)
   {
	   Node newNode = new Node(node);
	   
	   if(size == 0)
	   {
		   head = newNode;
	   }
	   else
	   {
		   Node curr = head;
		   while(curr.next != null)
		   {
			   curr = curr.next;
		   }
		   curr.next = newNode;
	   }
	   size++;
   }
   
   public void add(Comparable string)
   {
	   Node newNode = new Node(string);
	   if (size == 0)
	   {
		   head = newNode;
	   }
	   else
	   {
		   Node curr = head;
		   while (curr.next != null)
		   {
			   curr = curr.next;
		   }
		   curr.next = newNode;
	   }
	   size++;
   }

/*
   public void clear()
   {
	   head = null;
	   size = 0;
   }
	
   public String toString()
   {
	   String s = "";
	   if(head == null)
	   {
		   System.out.println("List is Empty!");
	   }
	   else
	   {
		   for(Node curr = head; curr != null; curr = curr.next)
		   {
			   s = s + curr.data + "\n";
		   }
	   }			
	   return s;
   }
	
   public void sort()
   {
	   Node position;
	   Node start;
		
	   if(size > 0)
	   {
		   for(position = head; position != null; position = position.next)
		   {
			   Node smallest = position;
			   for(start = position.next; start != null; start = start.next)
			   {
				   if((Integer)start.data < (Integer)smallest.data)
				   {
					   smallest = start;
				   }
			   }
			   Comparable temp = position.data;
			   position.data = smallest.data;
			   smallest.data = temp;
		   }
	   }
   }
	
   public void reverse()
   {
	   if(head == null)
	   {
		   System.out.println("The list is empty.");
	   }
	   reverse(head);
   }
	
   public void reverse(Node node)
   {
	   if(node != null)
	   {
		   reverse(node.next);
		   System.out.println(node.data);
	   }
		
   }
	
   public void listEven()
   {
	   for(Node curr = head; curr != null; curr = curr.next)
	   {
		   if((Integer)curr.data % 2 == 0)
		   {
			   System.out.println(curr.data);
		   }
	   }
   }
	
   public Node listEvery(int amt)
   {
	   Node curr;
		
	   for(curr = head; curr.next != null; curr = curr.next)
	   {
			
	   }
	   return curr;
   }
	
   public boolean removeN(int contains)
   {
	   Node prev = null;
	   Node curr = head;
	   while(curr != null)
	   {
		   if(curr.data.equals(contains))
		   {
			   curr = curr.next;
			   if(prev == null)
				   prev = curr;
			   else
				   prev.next = curr;
			   size--;
			   return true;
		   }
		   else
		   {
			   prev = curr;
			   curr = curr.next;
		   }
	   }
	   return false;
   }
	*/
}// end LinkedList class

Package

public class Package implements Comparable <Package>
{
	String tracking, weight;
	
	public Package(String tracking, String weight)
	{
		this.tracking = tracking;
		this.weight = weight;
	}
	
	public int getTracking() {
		return Integer.parseInt(tracking);
	}

	public int getWeight() {
		return Integer.parseInt(weight);
	}

	@Override
	public int compareTo(Package arg0) 
	{
		// TODO Auto-generated method stub
		return 0;
	}
	
	public String getType()
	{
		return this.getType();
	}

}

Box class

public class Box extends Package 
{
	private String length, width, height, type;

	public Box(String tracking, String weight, String length, String width, String height) 
	{
		super(tracking, weight);
		this.length = length;
		this.width = width;
		this.height = height;
		this.type = "Box";
	}

}

Letter

public class Letter extends Package
{
	private String length, width, type;
	
	public Letter(String tracking, String weight, String length, String width)
	{
		super(tracking, weight);
		this.length = length;
		this.width = width;
		this.type = "Letter";
	}

}

[Norm]

Does this code compile for you? I get errors.

Also will need the contents of the manifest.txt file.


Can you explain what the problem is?

[Clerek]

There is no problems with the code as far as I can tell, but I need to access the data in the linkedlist. I setup the linkedlist to contain objects of type package (some being box and some being letter). I just don't know how to access the data within the objects (tracking number, weight, length, width, height...)

Thanks

manifest.txt contents are:

Chris "King of the Road" Peters
3
123450
10
12
12
5555551
99
36
36
36
123890
25
10
10
656561
50
36
36
37
3456541
abc
5
5
5
879880
1
1
1
890980
2
2
2

[Norm]

There is no problems with the code as far as I can tell

How are you compiling the code? It will not compile for me.
See line 58 in Truck:
if(temp.head.)

I just don't know how to access the data within the objects

Use the classes's get... methods (or add some as needed)

[Clerek]

Thats the load class that I was working on before I got stuck. As far as the getters, how would you write the get? Ive got the singly linkedlist that contains the package (box and letter) objects. Which class should I put the getters in? Box and Letter? or Package?

Thanks again!

[Clerek]

That sounded like I can't write the get methods. I can, but am just confused as to where to put them...

[Norm]

The Package class already has get methods for its data. Add the class specific getters to the other classes where you need to get their data.

[Clerek]

Seriously? Jeez, I feel like I should have known that. I guess I've been working on it too much. Fresh set of eyes helps! I'll try that and post my results.

Thanks again for the help!