parameter passing (very beginner)

[Brian Rush]

Hi,
I'm trying to get the variable qty that was returned from the getUserInput method passed into the computeTotals method. It doesn't see the var qty being passed in. What am I doing wrong here? TIA!
Brian

 
import java.io.*;

class tvBill3 {
 // DataInputStream numberEntered = new DataInputStream (system.in);
  //String [] input = new String[5];
  double [] price = { 400, 220, 35.2, 300, 150 };
  double TAXRATE = 0.0825;

// main method...
  public static void main (String[] args)
    {
      getUserInput();
      computeTotals(qty);
    }

// getting user input and converting to integer...
   static int[] getUserInput()
    {
      String [] howManyCategory = { "TV's", "VCR's", "remote controllers", "CD's", "Tape Recorders" };
      int [] qty = new int [howManyCategory.length];
      for(int i=0; i < howManyCategory.length; i++)
       {
        String input = javax.swing.JOptionPane.showInputDialog("How many " + howManyCategory[i] + " were sold?");
        System.out.println("Input was " + input);
        qty[i]= Integer.parseInt(input);
        System.out.println("Quantity " + i + " was " + qty[i]);
       }
        return (qty);
     }

// Compute totals...
   static double computeTotals()
    {
      double [] extension = new double [qty.length];
      double [] price = { 400, 220, 35.2, 300, 150 };
      for(int i=0; i<qty.length; i++)
        {
          extension[i] = qty[i] * price[i];
        }
    }
}

[Ron Newman]

This doesn't compile. I get these errors:
tvBill3.java:17: cannot resolve symbol
symbol : variable qty
location: class tvBill3
computeTotals(qty);
^
tvBill3.java:45: cannot resolve symbol
symbol : variable qty
location: class tvBill3
double [] extension = new double [qty.length];
^
tvBill3.java:48: cannot resolve symbol
symbol : variable qty
location: class tvBill3
for(int i=0; i<qty.length; i++)
^
tvBill3.java:50: cannot resolve symbol
symbol : variable qty
location: class tvBill3
extension[i] = qty[i] * price[i];
^
Are you sure that you posted the exact source code that you are running?

[Brian Rush]

Those are the errors I get as well. The caret is pointing to the qty variable in each error. This is where my problem lies. I thought qty was returned back to the main method. Then it gets passed to the computeTotals method as a parameter. It is not being seen in the computeTotals method.
Thanks,
Brian

[Ron Newman]

You are referring to a variable called "qty" in your main() method, but there is no such variable declared in either the tvBill3 object or in the main() method.
You are calling computeTotals() with a "qty" parameter, but you have declared this method to take no arguments. You're also referring to "qty" inside the function, but you haven't declared it as either a variable or a parameter.

[Richard de Boer]

Originally posted by Brian Rush:
[QB]Hi,
I'm trying to get the variable qty that was returned from the getUserInput method passed into the computeTotals method. It doesn't see the var qty being passed in. What am I doing wrong here? TIA!
Brian
Good morning Brian,
In java a variable lives between the enclosing {}.
So you cannot ask for it outside the brackets.
There is a way around that called a return type. This is what you used in the correct way.
But when something is returned it loses it's name. So you have to store it again. And you are free to choose a new name!!!
A compile-able version of your code:

import java.io.*;
public class tvBill3 { 
// DataInputStream numberEntered = new DataInputStream (system.in);  //
private String [] input = new String[5];  
private double [] price = { 400, 220, 35.2, 300, 150 };  
private double TAXRATE = 0.0825;
// main method...  
public static void main (String[] args)    {  
// step 1 create an object of the class
    tvBill3 a =new tvBill3();
    
//step 2 let the object do things
a.getUserInput();      
System.out.println("***computeTotals();*** "+a.computeTotals());
//removed qty because the method is static double computeTotals() 
//and not static double computeTotals(qty) 
//second way...
System.out.println("***computeTotals(getUserInput());*** "+a.computeTotals(a.getUserInput()));
//In order to end the program 
System.exit(0);
}
// getting user input and converting to integer...   
 private int[] getUserInput()    {      
String [] howManyCategory = { "TV's", "VCR's", "remote controllers", "CD's", "Tape Recorders" }; 
     int [] qty = new int [howManyCategory.length];
     for(int i=0; i < howManyCategory.length; i++)     { 
       String input = javax.swing.JOptionPane.showInputDialog("How many " + howManyCategory[i] + " were sold?");
       System.out.println("Input was " + input); 
       try{
       qty[i]= Integer.parseInt(input); 
      }catch (NumberFormatException NFE){ 
        System.out.println("Sorry, I prefer numbers only");
        qty[i]=0;
      }
       System.out.println("Quantity " + i + " was " + qty[i]);
         }        
        return (qty);     
}// Compute totals...   
                                          
/**
 *The qty only exists in the method: static int[] getUserInput()
 *(a variable only lives between the 2 enclosing brackets)
 *The method returns an object of type int[]. But does not know how it is called.
 *So in the compuTotals i will give it a name...
 **/ 
                                          
 private double computeTotals()    { 
int []qty=getUserInput();
double [] extension = new double [qty.length]; 
    double [] price = { 400, 220, 35.2, 300, 150 };
    for(int i=0; i<qty.length; i++)        { 
        extension[i] = qty[i] * price[i];
    }  
    //let get the money calculated:
    double money=0.0d;
    for(int i=0; i<qty.length; i++)  
    money+=  extension[i];     
    return (money);  
}

//a differend way with the use of overloading
private double computeTotals(int []qty)    { 
double [] extension = new double [qty.length]; 
    double [] price = { 400, 220, 35.2, 300, 150 };
    for(int i=0; i<qty.length; i++)        { 
        extension[i] = qty[i] * price[i];
    }  
    //let get the money calculated:
    double money=0.0d;
    for(int i=0; i<qty.length; i++)  
    money+=  extension[i];
    return (money);  
}
}                                                   

Enjoy java,
Richard
(edited by Cindy to format code . . . hint, hint)
[ November 18, 2002: Message edited by: Cindy Glass ]

[Sam Zou]

Hi !

I'd like to known if this line works !
String input = javax.swing.JOptionPane.showInputDialog("How many " + howManyCategory[i] + " were sold?");
I try it and nothing happened ! The program just hang.

By the way, here is a working version of your program but without the Swing dialog box.

import java.io.*;
 
class ParameterPassing {
 
    // DataInputStream numberEntered = new DataInputStream (system.in);
    //String [] input = new String[5];
    double [] price = { 400, 220, 35.2, 300, 150 };
    double TAXRATE = 0.0825;
 
    // main method...
    public static void main (String[] args){
 
        System.out.println("Totals is :"+computeTotals(getUserInput()));
 
    }
 
    // getting user input and converting to integer...
    static int[] getUserInput()
    {
        String [] howManyCategory = { "TV's", "VCR's", "remote controllers", "CD's", "Tape Recorders" };
        int [] qty = new int [howManyCategory.length];
        for(int i=0; i < howManyCategory.length; i++){
            //String input = javax.swing.JOptionPane.showInputDialog("How many " + howManyCategory[i] + " were sold?");
            String input = "How many " + howManyCategory[i] + " were sold?";
            System.out.print(input);
            BufferedReader d = new BufferedReader(new InputStreamReader(System.in));
            try{
                qty[i]= Integer.parseInt(d.readLine());
            } catch(IOException ex){
                System.err.println(ex);
            }
            System.out.println("Quantity " + i + " was " + qty[i]);
        }
        return qty;
    }
 
    // Compute totals...
    static double computeTotals(int [] qty){
        double [] extension = new double [qty.length];
        double [] price = { 400, 220, 35.2, 300, 150 };
        for(int i=0; i<qty.length; i++){
            extension[i] = qty[i] * price[i];
        }
        double temp =0.0d;
        for(int i=0; i<extension.length; i++){
            temp += extension[i];
        }
        return temp;
    }
 
}//class

Thanks
[ edited to surround code with the [code] and [/code] UBB Tags so as to help preserve formatting and make the code easier to read -ds ]
[ November 18, 2002: Message edited by: Dirk Schreckmann ]