Need help with a class project

Question

I'm new to Java and I'm having problems converting a small program to be more functional. Here is my original codeimport java.util.Arrays;
public class Product
// initialize arrays
   private int cdNums[] = { 0,0,0,0 };
   private String cdNames[] = { "null", "null", "null", "null" };
   private int cdUnits[] = { 0,0,0,0 };
   private double cdValue[] = { 0.0, 0.0, 0.0, 0.0 };
   private double inventoryValue[] = { 0.0, 0.0, 0.0, 0.0 };
// initialize instance variable
   private double totalValue = 0;
   private int count;
   public Product( int invNumber[], String albumName[], int invUnits[], double invValue[] )
         cdNums = invNumber;  // store inventory number
         cdNames = albumName;  //store album name
         cdUnits = invUnits;  //store number of units
         cdValue = invValue; // store unit price
   public double calcInventoryValue()
         // calculate Inventory value
            for ( int count = 0; count < cdNums.length; count++ )
                   totalValue =0; // initialize totalValue
                   totalValue =( cdUnits[ count ] * cdValue [ count ] );
           System.out.printf( "%s%d%s%s%s%d%s%.2f%s%.2f\n", "Item #", cdNums[ count ], " is: ", cdNames[ count ], " with ", cdUnits [ count ], " units priced at $", cdValue [ count ], " gives value of $", totalValue );
         return totalValue;
      } // end calcinventoryValue method
} // end classand the test application: import java.util.Arrays;
public class ProductTest
   public static void main( String args[] )
        int invNumber [] = { 1,2,3,4 };
        String albumName[] = { "Wish You Were Here", "Abacab", "Animals", "Security" };
        int invUnits[] = { 200, 150, 50, 500 };
        double invValue[] = { 14.99, 9.99, 23.49, 12.99 };
     Product myProduct = new Product (invNumber, albumName, invUnits, invValue );       
        myProduct.calcInventoryValue();
     } // end main
} // end class ProductTestWhat I want to do is convert it to read in user input instead of static lists. Here is what I have so far:
import java.util.Arrays;
public class Product
// initialize arrays
   private int cdNums[];
   private String cdNames[];
   private int cdUnits[];
   private double cdValue[];
   private double inventoryValue[];
// initialize instance variable
   private double runValue = 0;
   private double totalValue = 0;
   private int count;
   public Product( int invNumber[], String albumName[], int invUnits[], double invValue[] )
         cdNums = invNumber;  // store inventory number
         cdNames = albumName;  //store album name
         cdUnits = invUnits;  //store number of units
         cdValue = invValue; // store unit price
   public double calcInventoryValue()
         // calculate Inventory value
            totalValue = 0; // Initialize totalValue variable
            for ( int count = 0; count < cdNums.length; count++ )
                   runValue =0; // initialize runValue
                   runValue =( cdUnits[ count ] * cdValue [ count ] );
           System.out.printf( "%s%d%s%s%s%d%s%.2f%s%.2f\n", "Item #", cdNums[ count ], " is: ", cdNames[ count ], " with ", cdUnits [ count ], " units priced at $", cdValue [ count ], " gives value of $", runValue );
                 totalValue = totalValue += runValue;
          calcTotalValue( totalValue );
         return totalValue;
      } // end calcinventoryValue method
    public double calcTotalValue( double totalValue )
         System.out.printf( "%s%.2f\n", "The total value of the inventory is: $", totalValue );
          return totalValue;
       } // end calcTotalValue method
} // end classand the new test application:
import java.util.Arrays;
import java.util.Scanner;
public class ProductTest
   public static void main( String args[] )
        double totalValue = 0;
      do 
        { //  open dowhile
         int count = 0; // initialize counter
         Scanner input = new Scanner( System.in ); // call scanner to get input
         for ( int count = 0; count > 0; count++ )
           {  // open for loop
                     System.out.printf ( "%s%d%s\n", "Please enter the inventory # of Item ", count, " or 0 to quit: " );  // prompt for inventory number or sentinel value
                      int invNumber[ count ] = input.nextInt();  // get user input of Item Number
             if ( invNumber[ count ] != 0 )  // check for sentinel
               {  // open if
                     System.out.printf ( "%s%d\n","Please enter the album name of Item #", invNumber[ count ] );  // prompt for album name
                     String albumName[ count ] = input.nextLine();  // get input album name
                     System.out.printf ( "%s%d\n", "Please enter the number of units in stock for Item #", invNumber[ count ] );  // prompt for number of units in stock
                     int invUnits[ count ] = input.nextint();  // input rate of payment
                     System.out.printf ( "%s%.2f\n", "Please enter the unit price for Item #", invNumber[ count ] );  // prompt for unit price
                     double unitValue = input.nextDouble();  // input rate of payment
                     System.out.println();  // print blank line for readability
               } // close if
            else
               {  // open else
                  Product myProduct = new Product (invNumber, albumName, invUnits, invValue );       
                     myProduct.calcInventoryValue();
               } // close else
           } // close for loop           
       } while ( invNumber != 0 );  // loop back to inputting employee name and close dowhile
    } // end main
} // end class ProductTestthe compiler is telling me for ProductTest that it is expecting "]" for the following line: int invNumber[ count ] = input.nextInt();Do I need to store the data in a variable first and then feed it into the array? What do I need to do to complete this code?

Answer 1

OK, yeah. Change the Product constructor so that it takes scalar values (as opposed to arrays) -- a single int for units in stock, and single String for name, etc.
Then you can create multiple objects of that class, one for each CD or whatever.
It makes sense to hardcode values in the ProductTest class, but not really in the Product class. Your ProductTest class is almost there. You know how in the main method you create a single Product object with those arrays? Change it so that you have a loop. Loop through the prices, album names, etc., and create a Product for each set of values. Then put the Product objects in an array, or better yet (and if you've covered it in class) into a Collection like a java.util.HashSet or a java.util.ArrayList.
You said you wanted to make it take values from user input, rather than hardcoded lists. Once you've made the above change, move on to doing that. You can read user input with a java.util.Scanner. Or you can use a java.io.BufferedReader. Did the prof say to use one particular method or another?