Can someone look at this with a new set of eyes and see what I am missing.
I am new to Java and this is kicking my tail.
This is a simple inventory application. I am using an array to store the variables in the Compactdisk class, and sort on the name when done.
I implimented a sub class to that named CdwArtist class since I had never done it before. (I wanted to see inheritance in action)
I have my array now using the CdwAction class like I should, everything compiles fine, but when I run it I get a NullPointerException when I enter STOP and exit my loop.
It looks to me as if I am missing something with my array, possibly crossing the name and the artist somehow, but I have stared at this so long it is just looking like garbage to me. Any help would be welcome.
Inventory class
- import java.util.*;
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public class Inventory
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{// begin class Inventory
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public static int maxlength = 0;
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public static CdwArtist[] sort(CdwArtist[] cds)
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{
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Arrays.sort(cds, 0, maxlength);
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return cds;
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}
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public static String toString(CdwArtist[] cds)
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{
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String toSend = "\n\n";
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for(int i = 0; i < maxlength; i ++)
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toSend = toSend + cds[i].getName() + "\n";
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return toSend;
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}
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public static void main(String[] args)
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{//begin method main
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// create cd Array
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CdwArtist[] cds = new CdwArtist[100];
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float totalValue = 0;
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Scanner input = new Scanner(System.in); // create scanner
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// begin display method
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System.out.print("Enter up to 99 CD Names or STOP to Exit: ");
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String nameInput = input.nextLine(); //read cd name
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maxlength ++;
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for(int i = 1; i < cds.length && !nameInput.equalsIgnoreCase("STOP"); i++)
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{// begin main While
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cds[i] = new CdwArtist();
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cds[i].setName(nameInput);
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System.out.print("Enter CD Artist Name: "); // prompt for artist name
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CdwArtist artist = new CdwArtist(input.nextLine());
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System.out.print("Enter Price of this CD: "); // prompt for price
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cds[i].setPrice(input.nextFloat()); // price input from user.
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while (cds[i].getPrice()<= 0)
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{// begin while
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System.out.print("Price Must Be Greater Than Zero. Enter Price: ");
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cds[i].setPrice(input.nextFloat()); // cd price loop from user.
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} // End while
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System.out.print("Enter CD Item Number: "); // prompt for cd item number
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cds[i].setItemno(input.nextInt()); // cds item number input from user
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System.out.print("Enter Number of these CDs in Stock: "); // prompt for cd stock
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cds[i].setNstock(input.nextInt()); // cds in stock input from user
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System.out.print("\n\nCD "+cds[i].getName()+", Item Number "+cds[i].getItemno()+","); // display name
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System.out.printf(" is worth %c%.2f.",'$', + cds[i].getPrice());//
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System.out.print("\nWe have "+ cds[i].getNstock()+" copies in stock,");
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System.out.printf(" making our inventory for this cd worth %c%.2f.\n", '$', + cds[i].getValue()); //inventory value
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if(cds[i].getValue() != -1) totalValue = totalValue + cds[i].getValue();
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System.out.printf("Combined Inventory for all CDs is Worth %c%.2f.\n\n\n", '$', + totalValue);
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System.out.print("Enter up to 99 CD Names or STOP to Exit: ");
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input=new Scanner(System.in); // internal loop prompt
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nameInput = input.nextLine(); //name input from user
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maxlength ++;
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} // End main While
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//System.out.println(toString(cds));
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System.out.println(toString(sort(cds)));
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System.out.print("Ending Program.");
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}// end method main
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} // end class Payroll
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then the compactdisk class I first set up (even though this should require no modification at all to impliment a subclass.
- import java.lang.Comparable;
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public class Compactdisk implements Comparable
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{// begin class
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//InventoryCD class has 5 fields
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private String name; // Name of cd
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private float price; // price of cd
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private int itemno; // item number of cd
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private int nstock; // how many units in stock
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private int i; // cd counter for array
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private float value; // value for single cd inventory
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//Compact disk class constructor
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public Compactdisk()
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// 4 fields need to be set up
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{
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name = "";
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price = 0;
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itemno = 0;
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nstock = 0;
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i = 0;
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value = 0;
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}
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// set values
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public void setName(String diskName)
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{
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name = diskName;
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}
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public void setPrice(float cdPrice)
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{
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price = cdPrice;
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}
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public void setItemno(int cdItemno)
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{
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itemno = cdItemno;
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}
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public void setNstock(int cdStock)
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{
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nstock = cdStock;
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}
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public void setValue(float cdValue)
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{
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value = cdValue;
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}
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public void seti(int Count)
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{
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i = Count;
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}
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// return values
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public String getName()
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{
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return (name);
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}
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public float getPrice()
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{
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return (price);
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}
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public int getItemno()
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{
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return (itemno);
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}
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public int getNstock()
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{
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return (nstock);
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}
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public int compareTo(Object in)
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{
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return ((Comparable)name.toLowerCase()).compareTo((Comparable)((Compactdisk)in).getName().toLowerCase());
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}
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// returns indivudual inventory value for a disk
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public float getValue()
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{
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return(price * nstock);
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}
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}// end class
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and then my new subclass. everything worked fine before I did this.
- import java.util.*;
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public class CdwArtist extends Compactdisk
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{
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// CdwArtist class adds one field
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public String artist; // artist performing on cd
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// Artist constructor
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public CdwArtist()
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{
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artist = "";
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}
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public CdwArtist(String in)
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{
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artist=in;
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}
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// get value
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public void setArtist(String in)
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{
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artist=in;
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}
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// return value
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public String getArtist()
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{
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return (artist);
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}
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} //End Class
Anyone?
