Solution for Mock Test (Available only until 10 Nov 2006)

import javax.swing.*;

public class VendingMachine {

  public static int readChoice() {
    String inputString;
    int choice;
    do {
      inputString = JOptionPane.showInputDialog(null,
                                                "Enter your choice of drink:\n"
                                                + "1. Coke (60 cents)\n"
                                                + "2. Pepsi (60 cents)\n"
                                                + "3. Soya Bean (50 cents)\n"
                                                + "4. Green Tea (70 cents)\n"
                                                + "5. Ice Coffee (80 cents)\n",
                                                "SP Vendimatic Vending Machine",
                                                JOptionPane.QUESTION_MESSAGE);
      choice = Integer.parseInt(inputString);

      if (choice < 1 || choice > 5) {
        JOptionPane.showMessageDialog(null,
                                      "Invalid input ! Please enter in the range from 1 to 5.",
                                      "Error",
                                      JOptionPane.ERROR_MESSAGE);
      }
    } while (choice < 1 || choice > 5);

    return choice;
  }

  public static int computeAndDisplayPrice(int choice) {
    int price = 0;
    switch (choice) {
      case 1:
      case 2:
        price = 60;
        break;
      case 3:
        price = 50;
        break;
      case 4:
        price = 70;
        break;
      case 5:
        price = 80;
    }
    JOptionPane.showMessageDialog(null,
                                  "Price is " + price + " cents");
    return price;
  }

  public static int readPayment(int price) {
    String inputString;
    int payment;
    do {
      inputString = JOptionPane.showInputDialog(null,
                                                "Please enter your payment ("
                                                + price + " - 100 cents):\n",
                                                "SP Vendimatic Vending Machine",
                                                JOptionPane.QUESTION_MESSAGE);
      payment = Integer.parseInt(inputString);

      if (payment < price) {
        JOptionPane.showMessageDialog(null,
                                      "Invalid input ! Please enter a minimum payment of " +
                                      price + " cents.",
                                      "Error",
                                      JOptionPane.ERROR_MESSAGE);
      } else if (payment > 100) {
        JOptionPane.showMessageDialog(null,
                                      "Invalid input ! Please do not enter more than 100 cents.",
                                      "Error",
                                      JOptionPane.ERROR_MESSAGE);
      }
    } while (payment < price || payment > 100);

    return payment;
  }

  public static int computeAndDisplayChange(int payment, int price) {
    int change;
    change = payment - price;
    JOptionPane.showMessageDialog(null, "Change is " + change + " cents.");
    return change;
  }

  public static void dispenseChange(int change) {
    int num50cents, num20cents, num10cents;
    int balance;

    num50cents = change / 50;
    balance = change % 50;

    num20cents = balance / 20;
    balance = balance % 20;

    num10cents = balance / 10;
    String s = "Dispensing...\n"
                                   + num50cents + " x 50c coin\n"
                                   + num20cents + " x 20c coin\n"
                                   + num10cents + " x 10c coin";

    JOptionPane.showMessageDialog(null, s );

  }

  public static void main(String[] args) {
    int choice;
    int price;
    int payment;
    int change;

    String inputString;

    char cont;

    do {
      choice = readChoice();
      price = computeAndDisplayPrice(choice);
      payment = readPayment(price);
      change = computeAndDisplayChange(payment, price);

      if (change > 0) {
        dispenseChange(change);
      }

      do {
        inputString = JOptionPane.showInputDialog(null,
                                                  "Do you want another drink (Y/N)?");
        cont = inputString.charAt(0);

        if (! (cont == 'Y' || cont == 'N' || cont == 'y' || cont == 'n')) {
          JOptionPane.showMessageDialog(null,
                                        "Invalid input ! Please enter Y or N.",
                                        "Error",
                                        JOptionPane.ERROR_MESSAGE);
        }
      }
      while (! (cont == 'Y' || cont == 'N' || cont == 'y' || cont == 'n'));

    }
    while (cont == 'Y' || cont == 'y');
    JOptionPane.showMessageDialog(null,
                                  "VendingMachine class program terminated.");

  } //end main

} //end class