Thread: Code Simplification

Ladies and Gentlemen,

I am writing a program for my Java 1 class. My code compiles and the end result is exactly what the professor wants. However, I don't think I did it exactly how it was wanted.

The instructions say "You will modify this problem to run for three salesmen. You will have the user enter each salesman’s name, the item number and the quantity for each item number. All input/output is through dialog boxes. You will use a for loop and a while loop."

I used a while loop with a switch statement (forgive me if that's the wrong way to say that), but I don't see how to incorporate a for loop in there.

Any help would be appreciated.

import javax.swing.JOptionPane;
import java.util.Scanner;
 
public class CalculatingSales
{
	public static void main(String args[])
	{
		Scanner input = new Scanner(System.in);
 
		int quantity;
		int itemNumber;
		String e1;
		String e2;
		String e3;
		double sales1 = 0.0;
		double sales2 = 0.0;
		double sales3 = 0.0;
		double product1 = 2.98;
		double product2 = 4.50;
		double product3 = 9.98;
		double product4 = 4.49;
		double product5 = 6.87;
 
		e1 =
			JOptionPane.showInputDialog("Enter salesman name");
 
		itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
		while (itemNumber != 0)
		{
			switch(itemNumber)
			{
				case 1: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales1 = sales1 + (quantity * product1);
					break;	
 
				case 2: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales1 = sales1 + (quantity * product2);
					break;	
 
				case 3: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales1 = sales1 + (quantity * product3);
					break;	
 
				case 4: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales1 = sales1 + (quantity * product4);
					break;	
 
				case 5: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales1 = sales1 + (quantity * product5);
					break;
 
				default: JOptionPane.showMessageDialog(null, "Invalid item number", "Error",
							JOptionPane.ERROR_MESSAGE);
			}
 
			itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));						
		}
 
		e2 =
			JOptionPane.showInputDialog("Enter salesman name");
 
		itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
		while (itemNumber != 0)
		{
			switch(itemNumber)
			{
				case 1: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales2 = sales2 + (quantity * product1);
					break;	
 
				case 2: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales2 = sales2 + (quantity * product2);
					break;	
 
				case 3: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales2 = sales2 + (quantity * product3);
					break;	
 
				case 4: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales2 = sales2 + (quantity * product4);
					break;	
 
				case 5: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales2 = sales2 + (quantity * product5);
					break;
 
				default: JOptionPane.showMessageDialog(null, "Invalid item number", "Error",
							JOptionPane.ERROR_MESSAGE);
			}
 
			itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));						
		}
 
		e3 =
			JOptionPane.showInputDialog("Enter salesman name");
 
		itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
		while (itemNumber != 0)
		{
			switch(itemNumber)
			{
				case 1: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales3 = sales3 + (quantity * product1);
					break;	
 
				case 2: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales3 = sales3 + (quantity * product2);
					break;	
 
				case 3: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales3 = sales3 + (quantity * product3);
					break;	
 
				case 4: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales3 = sales3 + (quantity * product4);
					break;	
 
				case 5: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
							sales3 = sales3 + (quantity * product5);
					break;
 
				default: JOptionPane.showMessageDialog(null, "Invalid item number", "Error",
							JOptionPane.ERROR_MESSAGE);
			}
 
			itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));						
		}
 
		String msg = 
					String.format("%s %s $%,.2f\n%s %s $%,.2f\n%s %s $%,.2f\n", 
					e1, "sales are", sales1, e2, "sales are", sales2,
					e3, "sales are", sales3);
 
		JOptionPane.showMessageDialog(null, msg);	
	}
}

Have you learned arrays yet? Maybe it doesn't matter.

Anytime you're repeating the exact same code, you should wonder, "How can I put this in a loop?" or "How can I write a method to do this?" In this case, you could do something like:

for ( int i = 0 ; i < 3 ; i++ )
{
	e1 =
		JOptionPane.showInputDialog("Enter salesman name");
 
	itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
	while (itemNumber != 0)
	{
		switch(itemNumber)
		{

But the salesman's info, name and sales, would have to either be stored or output each time through the for loop. This would be best accomplished using a class to hold each salesman's info, but I'm not sure what you're able to do.

We haven't learned arrays yet, and we are not allowed to build a class. I just can't figure out how the loop would switch to the different employee variables to hold the new information. Is this even possible?

You could use an if statement to record the correct data based on the value of the for loop's control variable, but that's almost (not quite) as much trouble as repeating the same code 3 times.

I ended up figuring it out. The part that I couldn't wrap my head around was how the final display message was going to remember the names and such. Once I understood how that would work it all just fell into place.

Thanks for your assistance.

import javax.swing.JOptionPane;
import java.util.Scanner;
 
public class CalculatingSales
{
	public static void main(String args[])
	{
		Scanner input = new Scanner(System.in);
 
		int quantity;
		int itemNumber;
		double sales = 0;
		double product1 = 2.98;
		double product2 = 4.50;
		double product3 = 9.98;
		double product4 = 4.49;
		double product5 = 6.87;
		String msg = "";
		String salesman;
 
		for (int i = 1; i <= 3; i++)
		{
			salesman = JOptionPane.showInputDialog("Enter salesman name");
 
			itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
			while (itemNumber != 0)
			{
				switch(itemNumber)
				{
					case 1: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
								sales = sales + (quantity * product1);
						break;	
 
					case 2: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
								sales = sales + (quantity * product2);
						break;	
 
					case 3: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
								sales = sales + (quantity * product3);
						break;	
 
					case 4: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
								sales = sales + (quantity * product4);
						break;	
 
					case 5: quantity = Integer.parseInt(JOptionPane.showInputDialog("Enter quantity"));
								sales = sales + (quantity * product5);
						break;
 
					default: JOptionPane.showMessageDialog(null, "Invalid item number", "Error",
								JOptionPane.ERROR_MESSAGE);
				}
 
				itemNumber = Integer.parseInt(JOptionPane.showInputDialog("Enter item number"));
 
			}
 
			msg = msg +
				String.format("%s %s $%,.2f\n", salesman, "sales are", sales);
 
		}
 
		JOptionPane.showMessageDialog(null, msg);	
 
	}
}

Good job! In summary, add the results of each loop to a String object and output the completed String object after exiting the loop.