How do I use a (boolean?) token to reject user input?

[Michael Fraczek]

I have a program in which a user buys an item at a store. I have the user input the itemName, quantity, unitPrice, and whether it is taxable or not in a String which is tokenized into four parts, delimited by the "|" character.
Example: itemName|quantity|unitPrice|N
The N or n in the fourth token tells whether the purchase is taxable.
How can I use Java to reject the input and display an error message to the user if the fourth token is not input as a "n" or a "N"?
Any help is greatly appreciated!

[Michael Fraczek]

Here is a sample of the code I have written so far:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import javax.swing.JOptionPane;
class MorePurchases
{
    public static void main (String [] args)
    {
        double TAX_RATE = 0.05;
        boolean taxable;
        String itemName = null;
        int quantity = 0;
        double unitPrice = 0.0;
        double cost = 0.0;
        char n;
        char N;
        JOptionPane.showMessageDialog(null,
           "This program processes information about the purchase of one \nitem " +
           "at a retail store using JOptionPane for input and output\n" +
           "while validating data and implemention conditional options.");
        String nameQuantUPriceString = JOptionPane.showInputDialog(
           "Please enter the name of the item being purchased, the quantity desired\n" +
           "(as an integer), the unit price, and if the item is not subject to sales tax" +
           ", using the form:\n\n" + "itemName|quantity|unitPrice|N\n\n" +
           "Example:  3-ring notebook paper, pkg|6|0.95" + "      (for a taxable item)\n" +
           "or\n" + "MSDN MAgazine|4|5.95|N" + "                                        " +
           "  (for a non-taxable item)\n\n");
        StringTokenizer nameQuantUPrice = new StringTokenizer (nameQuantUPriceString, "|$");
        if (nameQuantUPrice.countTokens() == 3)
        {
        itemName = nameQuantUPrice.nextToken();
        String quantityString = nameQuantUPrice.nextToken();
        quantity = Integer.parseInt(quantityString);
        String unitPriceString = nameQuantUPrice.nextToken();
        unitPrice = Double.parseDouble(unitPriceString);
        }
        else
        {
            if (nameQuantUPrice.countTokens() == 4)
            {
                itemName = nameQuantUPrice.nextToken();
                String quantityString = nameQuantUPrice.nextToken();
                quantity = Integer.parseInt(quantityString);
                String unitPriceString = nameQuantUPrice.nextToken();
                unitPrice = Double.parseDouble(unitPriceString);
                String taxableBoolean = nameQuantUPrice.nextToken();
                
            }
            else
            {
                JOptionPane.showMessageDialog(null,
                  "Sorry, you entered too many or too few item charactaristics.\n\n" + "Next time"+
                  ":\n\nPlease enter the name of the item being purchased, the quantity desired\n" +
                  "(as an integer), the unit price, and if the item is not subject to sales tax" +
                  ", using the form:\n\n" + "itemName|quantity|unitPrice|N\n\n" +
                  "Example:  3-ring notebook paper, pkg|6|0.95" + "      (for a taxable item)\n" +
                  "or\n" + "MSDN MAgazine|4|5.95|N" + "                                        " +
                  "  (for a non-taxable item)\n\n");
                System.exit(0);
            }
        }
        cost = quantity * unitPrice * (1.00 + TAX_RATE);
        cost = (int) (cost * 100.0 + 0.5) / 100.0;
        JOptionPane.showMessageDialog(null,
           "Item:                            " + itemName + "\n" +
           "Quantity:                                          " + quantity + "\n" +
           "Unit price:                                $" + unitPrice + "\n" +
           "Subtotal:                                  $" + cost + "\n" +
           "Discount:                                 $" + "\n" +
           "Pre-tax total:                          $" + "\n" +
           "Sales tax:                                $" + "\n" +
           "Total:                                        $ ");

    }
}

[ November 30, 2002: Message edited by: Marilyn de Queiroz ]

[Ruben Steins]

Perhaps you could use:
[QOUTE]

public boolean endsWith(String suffix)

Tests if this string ends with the specified suffix.

of you could use:

public boolean matches(String regex)

if you're into regular expressions...