Thread: Dorm and Meal Plan Calculator

I'm a bit confused about my program. I have it all working great, but my professor is expecting a different output. He wants a box where you select your dormitory and meal plan, with "Calculate charges" and "Exit" buttons. When you click "Calculate charges," a second box comes up with a message with your total charges. I've tried other stuff like:

		JOptionPane.showMessageDialog(total,
			    "Total Charges For the Semester: ");

But with no luck. Any tips or suggestions on how to rewrite my code to satisfy my professor will be greatly appreciated. Thanks

Here's my code:

import java.awt.*;	        // Import common GUI elements.
import java.awt.event.*;	// Import common GUI event listeners.
import javax.swing.*;		// Import more common GUI elements.
 
/** DormAndMealPlanCalculator class. */
public class DormAndMealPlanCalculator extends JFrame
{
	private static final long serialVersionUID = 1L;
	private JLabel label;				// Display a message.
	private JPanel dormPanel;			// To hold dorm panel components.
	private JPanel selectedDormPanel;		// To hold selected dorm panel components.
	private JComboBox dormBox;			// List of dorms.
	private JTextField selectedDorm;		// Selected dorm.
	private JPanel mealPanel;			// To hold meal panel components.
	private JPanel selectedMealPanel;		// To hold selected meal panel components.
	private JComboBox mealBox;			// List of meal plans.
	private JTextField selectedMeal;		// Selected meal plan.
	private JPanel totalPanel;			// To hold total panel component.
	private JTextField total;			// Total plan.
 
	/** Array to hold the values of the dormitory
	    combo box. */
	private String[] dorm =
		{
			"Allen Hall $" + 1500, "Pike Hall $" + 1600, 
			"Farthing Hall $" + 1200, "University Suites $" + 1800
		};
 
	/** Array to hold the dormitory rate. */
	double[] dRate = {1500, 1600, 1200, 1800};
 
	/** Array to hold the values of the meal
	    combo box. */
	private String[] meal =
		{
			"7 Meals Per Week $" + 560,
			"14 Meals Per Week $" + 1095,
			"Unlimited Meals $" + 1500
		};
 
	/** Array to hold the meal plan rate. */
	double[] mRate = {560, 1095, 1500};
 
	/** Constructor. */
	public DormAndMealPlanCalculator()
	{
		setTitle("Dorm and Meal Plan Calculator.");		// Set the title.
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);		// Specify action for close button.
		setLayout(new GridLayout(3,2));				// Create a border layout manager.
 
		// Build panels.
		buildDormPanel();
		buildMealPanel();
		buildTotalPanel();
 
		// Add panels to content pane.
		add(dormPanel);
		add(mealPanel);
		add(totalPanel);
 
		// Pack and display.
		pack();
		setVisible(true);
	}
 
	/** buildDormPanel function that adds a combo box
	    with the dormitories to the panel. */
	private void buildDormPanel()
	{
		dormPanel = new JPanel();	// Create panel to hold combo box.
		dormBox = new JComboBox(dorm);	// Create the combo box.
 
		// Register an action listener. 
		dormBox.addActionListener(new ComboBoxListener());
		dormPanel.add(dormBox);
	}
 
 
	/** buildMealPanel function that adds a combo box
	    with the types of meals to the panel. */
	private void buildMealPanel()
	{
		mealPanel = new JPanel();		// Create panel to hold combo box.
		mealBox = new JComboBox(meal);	// Create the combo box.
 
		// Register an action listener.
		mealBox.addActionListener(new ComboBoxListener());
		mealPanel.add(mealBox);
	}
 
	/** buildSelectedDormPanel function adds a
	    read-only text field to the panel. */
	public void buildSelectedDormPanel()
	{
		selectedDormPanel = new JPanel();		// Create panel to hold components.
		label = new JLabel("Your Dormitory Is: ");	// Create the label.
 
		// Create the uneditable text field.
		selectedDorm = new JTextField(20);
		selectedDorm.setEditable(false);
 
		// Add the label and text field
		// to the panel.
		selectedDormPanel.add(label);
		selectedDormPanel.add(selectedDorm);
	}
 
	/** buildSelectedMealPanel function adds a
	    read-only text field to the panel. */
	public void buildSelectedMealPanel()
	{
		selectedMealPanel = new JPanel();		// Create panel to hold components.
		label = new JLabel("Your Meal Plan Is: ");	// Create the label.
 
		// Create the uneditable text field.
		selectedMeal = new JTextField(20);
		selectedMeal.setEditable(false);
 
		// Add the label and text field
		// to the panel.
		selectedMealPanel.add(label);
		selectedMealPanel.add(selectedMeal);
	}
 
	/** buildTotalPanel function adds a
	  read-only text field to the panel. */
	private void buildTotalPanel()
	{
		totalPanel = new JPanel();						// Create the panel.
		label = new JLabel("Your Total Charges For the Semester Is: $");	// Create the label.
 
		// Create the uneditable text field.
		total = new JTextField(15);
		total.setEditable(false);
 
		// Add the label and text field
		// to the panel.
		totalPanel.add(label);
		totalPanel.add(total);
	}
 
	/** Private inner class that handles the event when the
	    user selects an item from the combo box. */
	private class ComboBoxListener implements ActionListener
	{
		public void actionPerformed(ActionEvent e)
		{
			// Declare variables.
			int dorm;
			int meal;
			double total1;		// String total.
 
			// Get the selected dormitory.
			dormBox.getSelectedItem();
			dorm = dormBox.getSelectedIndex();
 
			// Get the selected meal plan.
			mealBox.getSelectedItem();
			meal = mealBox.getSelectedIndex();
 
			// Add the selections.
			total1 = dRate[dorm] + mRate[meal];
			total.setText("$" + total1);
		}
	}
 
	/** Main function. */
	public static void main(String[] args) 
	{
		new DormAndMealPlanCalculator();
	}
 
}

What do you mean, "But with no luck." Do you mean it didn't meet your professor's requirements, or is it not working?

A JDialog is similar to a JFrame, but it provides the option of choosing its modality. It's an excellent choice for a child dialog to a main JFrame. Perhaps that's what your professor is looking for if s/he's not thrilled with the JOptionPane.

When I tried using the

JOptionPane.showMessageDialog(total,
			    "Total Charges For the Semester: ");

,

that box pops up but without the total charges and then I get errors in the console like:

Exception in thread "main" java.lang.NullPointerException
	at java.awt.Container.addImpl(Unknown Source)
	at java.awt.Container.add(Unknown Source)
	at chapter12.DormAndMealPlanCalculator.buildTotalPanel(DormAndMealPlanCalculator.java:149)
	at chapter12.DormAndMealPlanCalculator.<init>(DormAndMealPlanCalculator.java:62)
	at chapter12.DormAndMealPlanCalculator.main(DormAndMealPlanCalculator.java:181)

Oh, and it's not meeting his requirements. See if I run my code now, everything displays in one box/pane with the total charges for the semester. He is not looking for that, he is looking for this:

You have most of the needed parts, not all in the right places, and you're missing the two buttons.

Create and add two JButtons to the JFrame, perhaps in another JPanel replacing the total JPanel, add the appropriate action listeners to the JButtons, and then use a JDialog to display the existing total panel in response to selection of the calculate button.

Okay, I'll try that, thanks for the tips.