Class and Sub Class

I thought I understood how this worked, but maybe I do not.
I intentionally left a field out of my compactdisk class (artist) so that I could create a sub class later, impliment it, and see how that whole thing worked.
Sounded simple, I still think it is, I just think I am doing something wrong.
Here is my original class:
[CODE][import java.lang.Comparable;

public class Compactdisk implements Comparable
{// begin class

//InventoryCD class has 5 fields
private String name; // Name of cd
private float price; // price of cd
private int itemno; // item number of cd
private int nstock; // how many units in stock
private int i; // cd counter for array
private float value; // value for single cd inventory

//Compact disk class constructor
public Compactdisk()

// 4 fields need to be set up
{
name = "";
price = 0;
itemno = 0;
nstock = 0;
i = 0;
value = 0;
}

// set values
public void setName(String diskName)
{
name = diskName;
}
public void setPrice(float cdPrice)
{
price = cdPrice;
}
public void setItemno(int cdItemno)
{
itemno = cdItemno;
}
public void setNstock(int cdStock)
{
nstock = cdStock;
}
public void setValue(float cdValue)
{
value = cdValue;
}
public void seti(int Count)
{
i = Count;
}

// return values
public String getName()
{
return (name);
}
public float getPrice()
{
return (price);
}
public int getItemno()
{
return (itemno);
}
public int getNstock()
{
return (nstock);
}
public int compareTo(Object in)
{
return ((Comparable)name.toLowerCase()).compareTo((Comparable)((Compactdisk)in).getName().toLowerCase());
}

// returns indivudual inventory value for a disk
public float getValue()
{
return(price * nstock);
}

}// end class
/CODE]
It works ok, does what I want it to do.
I then created this sub class just for cd artist that I thought would just add to it.

import java.util.*;

public class Cdartist extends Compactdisk
{
 private String artist; // artist performing on cd
 
 // Artist constructor
 public Cdartist()
 {
 artist = "";
 }
 
 // set value
 public void setCdArtist(String cdArtist)
 	{ 
 	artist = cdArtist;
	}
		
	// return value
	public String getCdArtist()
	{
	return (artist);
	}
	
	
} //End Class

My understanding was that this new sub class is just an extention of the original and could be used with little or no extra effort. So I changed my Inventory application to include this object accordingly.

import java.util.*;

public class Inventory 
{// begin class Inventory

 public static int maxlength = 0;
  public static Compactdisk[] sort(Compactdisk[] cds)
   { 
	Arrays.sort(cds, 0, maxlength); 
	return cds;
	}
	
 public static String toString(Compactdisk[] cds)
  { 
  	String toSend = "\n\n"; 
	
	for(int i = 0; i < maxlength; i ++)
	toSend = toSend + cds[i].getName() + "\n";
	return toSend;
  } 
  
  public static void main(String[] args)
  {//begin method main
  
   // create cd Array 
	Compactdisk[] cds = new Compactdisk[100];
	
	cds[0] = new Compactdisk(); 
	float totalValue = 0; 
	
	Scanner input = new Scanner(System.in); // create scanner 
	
	// begin display method 
	System.out.print("Enter up to 99 CD Names or STOP to Exit: "); 
	String nameInput = input.nextLine(); //read cd name 
	
	maxlength ++; 
	
	 for(int i = 1; i < cds.length && !nameInput.equalsIgnoreCase("STOP"); i++)
	 {// begin main While
	  cds[i] = new Compactdisk();
	  cds[i].setName(nameInput);
	  
<strong>	  System.out.print("Enter CD Artist Name: "); // prompt for artist name
	 // input=new Scanner(System.in); 
	  cds[i].setCdArtist(input.nextLine()); // artist name input from user
	  </strong>
	  
	  System.out.print("Enter Price of this CD: "); // prompt for price
	  cds[i].setPrice(input.nextFloat()); // price input from user. 
	  while (cds[i].getPrice()<= 0) 
	 	{// begin while 
	   	System.out.print("Price Must Be Greater Than Zero. Enter Price: ");
			cds[i].setPrice(input.nextFloat()); // cd price loop from user.
	  	} // End while 
	  
	  System.out.print("Enter CD Item Number: "); // prompt for cd item number
	  cds[i].setItemno(input.nextInt()); // cds item number input from user 
	  
	  System.out.print("Enter Number of these CDs in Stock: "); // prompt for cd stock 
	  cds[i].setNstock(input.nextInt()); // cds in stock input from user
	  
	  System.out.print("\n\nCD "+cds[i].getName()+", Item Number "+cds[i].getItemno()+","); // display name 
	  System.out.printf(" is worth %c%.2f.",'$', + cds[i].getPrice());//
	  System.out.print("\nWe have "+ cds[i].getNstock()+" copies in stock,");
	  System.out.printf(" making our inventory for this cd worth %c%.2f.\n", '$', + cds[i].getValue()); //inventory value 
	 
	  if(cds[i].getValue() != -1) totalValue = totalValue + cds[i].getValue();
	  System.out.printf("Combined Inventory for all CDs is Worth %c%.2f.\n\n\n", '$', + totalValue);
	  
	  System.out.print("Enter up to 99 CD Names or STOP to Exit: "); 
	  input=new Scanner(System.in); // internal loop prompt 
	  nameInput = input.nextLine(); //name input from user 
	  
	  maxlength ++; 
	  } // End main While
	  
	   //System.out.println(toString(cds));
		System.out.println(toString(sort(cds))); 
		System.out.print("Ending Program."); 

   }// end method main 
} // end class Payroll

I am getting a cannot find symbol error on the new code. This usually means there is a problem with that object, I am guessing Inventory cannot find it. Do I have it set up wrong, or is my logic screwy?
Thanks for any help.

no1zson

Posting Whiz in Training

226 posts since Jul 2007

Reputation Points: 59

Solved Threads: 1

Class and Sub Class

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