Question

In this practice program you are going to practice creating graphical user interface controls and placing them on a form. You are given a working NetBeans project shell to start that works with a given Invoice object that keeps track of a product name, quantity of the product to be ordered and the cost of each item. You will then create the necessary controls to extract the user input and display the results of the invoice.

If you have any questions or need help post a question in the Practice/Programming Help in the Introduction & Resources module.

Review the Project Shell

Download the Netbeans Project WK2_Practice_Invoice - Shell.zip, unzip the project and open it up in NetBeans.

Carefully review the structure of the program and the given classes. Make sure you understand the structure before you attempt to modify the program. You can run the program, but you will see a blank form until you complete the steps below.

Modify the program code

In the program code you will see several "TODO" comments (you can select "Window|Action Items" to see a list of the TODOs, clicking on an item will jump you to the place in the code).

You will create the GUI components and add the controls to the form for: (naming of the controls as shown is important!)

Product name label

Product name textfield (name: txtProductName)

Quantity label

Quantity textfield (name: txtQuantity)

Item cost label

Item cost textfield (name: txtCost)

JButton to calculate the cost (name: btnCalculate)

Add a CalculateHandler handler object to the btnCalculate addActionListener

Your final working program will look something like the following (note this is an example only, your form will look different).

Week 2 Practice Program?-Invoice Product Name Coffee Cup Product Quantity (1 to 1000) 100 Item cost (10 to 10000) 10 Invoice Information: Product Name: Coffee Cup Number of items: 100 Price Per Item: $10.00 Total cost: $1,000.00 Total cost Calculate Total Cost

It has three class files.

Invoice.java

package business;

import java.text.NumberFormat;
import java.util.Locale;

public class Invoice {
  
private String productName;
private int quantityPurchased;
private double pricePerItem;

public Invoice() {
setProductName("");;
setQuantityPurchased(1);
setPricePerItem(10);
}
public Invoice(String productName, int quantityPurchased, double pricePerItem) {
setProductName(productName);
setQuantityPurchased(quantityPurchased);
setPricePerItem(pricePerItem);
}
public String getProductName() {
return productName;
}
public void setProductName(String productName) {
if(productName != null && !productName.trim().isEmpty()) {
this.productName = productName;
}
else {
this.productName = "Unknown product";
}
}
public int getQuantityPurchased() {
return quantityPurchased;
}
public void setQuantityPurchased(int quantityPurchased) {
if (quantityPurchased >= 1 && quantityPurchased <= 1000) {
this.quantityPurchased = quantityPurchased;
}
else if (quantityPurchased < 1) {
this.quantityPurchased = 1;
}
else {
this.quantityPurchased = 1000;
}
}
public double getPricePerItem() {
return pricePerItem;
}
public void setPricePerItem(double pricePerItem) {
if (pricePerItem >= 10 && pricePerItem <= 10000) {
this.pricePerItem = pricePerItem;
}
else if (pricePerItem < 10) {
this.pricePerItem = 10;
}
else {
this.pricePerItem = 10000;
}
}
public double getTotalCost() {
return pricePerItem * quantityPurchased;
}
@Override
public String toString() {
NumberFormat cf = NumberFormat.getCurrencyInstance(Locale.US);
StringBuilder str = new StringBuilder();
str.append("Invoice Information:");
str.append("\nProduct Name: ");
str.append(productName);
str.append("\nNumber of items: ");
str.append(quantityPurchased);
str.append("\nPrice Per Item: ");
str.append(cf.format(pricePerItem));
str.append("\nTotal cost: ");
str.append(cf.format(getTotalCost()));
return str.toString();
}
}

Invoice_GUI.java

package presentation;

import business.Invoice;
import java.awt.Dimension;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.GridLayout;
import java.awt.Insets;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Invoice_GUI extends JFrame {
  
public static final int WINDOW_WIDTH = 450;
public static final int WINDOW_HEIGHT = 400;
  
private Invoice aInvoice;
  
private JButton btnCalculate;
private JButton btnClear;
private JButton btnExit;
  
private JTextField txtProductName;
private JTextField txtQuantity;
private JTextField txtCostPerItem;
private JTextArea txtTotalCost;
  
public Invoice_GUI() {
super();
createPanel();
setFrame();
}
  
private void createPanel() {
super.setLayout(new GridLayout(0, 2));
//TODO: create the GUI components and add them to the form for:
/*
1. Product name label
2. Product name textfield (name: txtProductName)
3. Quantity label
4. Quanitity textfield (name: txtQuantity)
5. Item cost label
6. Item cost textfield (name: txtCost)
7. JButton to calculate the cost (name: btnCalculate
8. Add a CalculateHandler handler object to the btnCalculate addActionListener
*/
}
private void setFrame() {
Dimension windowSize = new Dimension(WINDOW_WIDTH, WINDOW_HEIGHT);

super.setTitle("Week 2 Practice Program--Invoice");
super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

super.setSize(windowSize);
super.setMinimumSize(windowSize);
super.setMaximumSize(windowSize);

super.setLocationRelativeTo(null);
super.setVisible(true);
}
private class CalculateHandler implements ActionListener {
@Override
public void actionPerformed(ActionEvent ae) {
boolean valid;
if (aInvoice == null) {
//TODO: create a new invoice object
aInvoice = new Invoice();
}
aInvoice.setProductName(txtProductName.getText());

try {
int quanity = Integer.parseInt(txtQuantity.getText());
aInvoice.setQuantityPurchased(quanity);
valid = true;
}
catch (NumberFormatException ex) {
JOptionPane.showMessageDialog(null, "Quantity needs to be a number between 1 and 1000",
"Illegal Quanity value",
JOptionPane.ERROR_MESSAGE);
valid = false;
txtQuantity.setText("");
txtQuantity.requestFocus();
}
if (valid) {
try {
double cost = 0;
//TODO: write the state to extract the double value from the txtCost field
aInvoice.setPricePerItem(cost);
}
catch (NumberFormatException ex) {
valid = false;
JOptionPane.showMessageDialog(null, "Costs needs to be a number between 10 and 10000",
"Illegal Cost value",
JOptionPane.ERROR_MESSAGE);
valid = false;
txtCostPerItem.setText("");
txtCostPerItem.requestFocus();
}
}
if (valid) {
//TODO: using the toString method of the invoice object to set the output text
}
}
}

@Override
public String toString() {
return "Invoice_GUI{" + "aInvoice=" + aInvoice + ", btnCalculate=" + btnCalculate + ", btnClear=" + btnClear + ", btnExit=" + btnExit + ", txtProductName=" + txtProductName + ", txtQuantity=" + txtQuantity + ", txtCostPerItem=" + txtCostPerItem + ", txtTotalCost=" + txtTotalCost + '}';
}
  
}

Invoice_Main.java

package presentation;

import java.util.Scanner;

public class Invoice_Main {

  

public static void main(String[] args) {

new Invoice_GUI();

Scanner sc = new Scanner(System.in);

System.out.println("Enter the name of the Product");

invoice.setProductName(sc.nextLine());

System.out.println("Enter the Quantity Purchased");

invoice.setQuantityPurchased(sc.nextInt());

System.out.println("Enter the price of the item");

invoice.setPricePerItem(sc.nextDouble());

System.out.println("\nProduct Purchased : " + invoice.getProductName());

System.out.println("Total Cost : " + invoice.invoiceAmount());

}

}

  

Answer 1

I have completed the required program for you. Added all the labels, textfields, and registered the button click listener to find and set the cost appropriately. Thanks

// Invoice_GUI.java

import java.awt.Dimension;

import java.awt.GridBagConstraints;

import java.awt.GridBagLayout;

import java.awt.GridLayout;

import java.awt.Insets;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JOptionPane;

import javax.swing.JTextArea;

import javax.swing.JTextField;

public class Invoice_GUI extends JFrame {

                public static final int WINDOW_WIDTH = 450;

                public static final int WINDOW_HEIGHT = 400;

                private Invoice aInvoice;

                private JButton btnCalculate;

                private JButton btnClear;

                private JButton btnExit;

                private JTextField txtProductName;

                private JTextField txtQuantity;

                private JTextField txtCost;

                private JTextArea txtTotalCost;

                public Invoice_GUI() {

                                super();

                                createPanel();

                                setFrame();

                }

                private void createPanel() {

                                super.setLayout(new GridLayout(0, 2));

                                // creating the GUI components and adding them to the form for:

                                /*

                                * 1. Product name label 2. Product name textfield (name:

                                * txtProductName) 3. Quantity label 4. Quanitity textfield (name:

                                * txtQuantity) 5. Item cost label 6. Item cost textfield (name:

                                * txtCost) 7. JButton to calculate the cost (name: btnCalculate 8. Add

                                * a CalculateHandler handler object to the btnCalculate

                                * addActionListener

                                */

                                add(new JLabel("Product Name"));

                                txtProductName = new JTextField();

                                add(txtProductName);

                                add(new JLabel("Product Quantity (1 to 1000)"));

                                txtQuantity = new JTextField();

                                add(txtQuantity);

                                add(new JLabel("Item cost (10 to 10000)"));

                                txtCost = new JTextField();

                                add(txtCost);

                                add(new JLabel("Total Cost"));

                                txtTotalCost = new JTextArea();

                                txtTotalCost.setEditable(false);

                                add(txtTotalCost);

                                btnCalculate = new JButton("Calculate total cost");

                                add(btnCalculate);

                                //adding button click handler

                                btnCalculate.addActionListener(new CalculateHandler());

                }

                private void setFrame() {

                                Dimension windowSize = new Dimension(WINDOW_WIDTH, WINDOW_HEIGHT);

                                super.setTitle("Week 2 Practice Program--Invoice");

                                super.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                                super.setSize(windowSize);

                                super.setMinimumSize(windowSize);

                                super.setMaximumSize(windowSize);

                                super.setLocationRelativeTo(null);

                                super.setVisible(true);

                }

                private class CalculateHandler implements ActionListener {

                                @Override

                                public void actionPerformed(ActionEvent ae) {

                                                boolean valid;

                                                if (aInvoice == null) {

                                                                //creating a new invoice object

                                                                aInvoice = new Invoice();

                                                }

                                                aInvoice.setProductName(txtProductName.getText());

                                                try {

                                                                int quanity = Integer.parseInt(txtQuantity.getText());

                                                                aInvoice.setQuantityPurchased(quanity);

                                                                valid = true;

                                                } catch (NumberFormatException ex) {

                                                                JOptionPane.showMessageDialog(null,

                                                                                                "Quantity needs to be a number between 1 and 1000",

                                                                                                "Illegal Quanity value", JOptionPane.ERROR_MESSAGE);

                                                                valid = false;

                                                                txtQuantity.setText("");

                                                                txtQuantity.requestFocus();

                                                }

                                                if (valid) {

                                                                try {

                                                                                double cost = 0;

                                                                                // extracting the double value from

                                                                                // the txtCost field

                                                                                cost = Double.parseDouble(txtCost.getText());

                                                                                aInvoice.setPricePerItem(cost);

                                                                } catch (NumberFormatException ex) {

                                                                                valid = false;

                                                                                JOptionPane.showMessageDialog(null,

                                                                                                                "Costs needs to be a number between 10 and 10000",

                                                                                                                "Illegal Cost value", JOptionPane.ERROR_MESSAGE);

                                                                                valid = false;

                                                                                txtCost.setText("");

                                                                                txtCost.requestFocus();

                                                                }

                                                }

                                                if (valid) {

                                                                // using the toString method of the invoice object to set

                                                                // the output text

                                                                txtTotalCost.setText(aInvoice.toString());

                                                                pack();

                                                }

                                }

                }

                @Override

                public String toString() {

                                return "Invoice_GUI{" + "aInvoice=" + aInvoice + ", btnCalculate="

                                                                + btnCalculate + ", btnClear=" + btnClear + ", btnExit="

                                                                + btnExit + ", txtProductName=" + txtProductName

                                                                + ", txtQuantity=" + txtQuantity + ", txtCostPerItem="

                                                                + txtCost + ", txtTotalCost=" + txtTotalCost + '}';

                }

}

// Invoice.java

import java.text.NumberFormat;

import java.util.Locale;

public class Invoice {

                private String productName;

                private int quantityPurchased;

                private double pricePerItem;

                public Invoice() {

                                setProductName("");

                                setQuantityPurchased(1);

                                setPricePerItem(10);

                }

                public Invoice(String productName, int quantityPurchased,

                                                double pricePerItem) {

                                setProductName(productName);

                                setQuantityPurchased(quantityPurchased);

                                setPricePerItem(pricePerItem);

                }

                public String getProductName() {

                                return productName;

                }

                public void setProductName(String productName) {

                                if (productName != null && !productName.trim().isEmpty()) {

                                                this.productName = productName;

                                } else {

                                                this.productName = "Unknown product";

                                }

                }

                public int getQuantityPurchased() {

                                return quantityPurchased;

                }

                public void setQuantityPurchased(int quantityPurchased) {

                                if (quantityPurchased >= 1 && quantityPurchased <= 1000) {

                                                this.quantityPurchased = quantityPurchased;

                                } else if (quantityPurchased < 1) {

                                                this.quantityPurchased = 1;

                                } else {

                                                this.quantityPurchased = 1000;

                                }

                }

                public double getPricePerItem() {

                                return pricePerItem;

                }

                public void setPricePerItem(double pricePerItem) {

                                if (pricePerItem >= 10 && pricePerItem <= 10000) {

                                                this.pricePerItem = pricePerItem;

                                } else if (pricePerItem < 10) {

                                                this.pricePerItem = 10;

                                } else {

                                                this.pricePerItem = 10000;

                                }

                }

                public double getTotalCost() {

                                return pricePerItem * quantityPurchased;

                }

                @Override

                public String toString() {

                                NumberFormat cf = NumberFormat.getCurrencyInstance(Locale.US);

                                StringBuilder str = new StringBuilder();

                                str.append("Invoice Information:");

                                str.append("\nProduct Name: ");

                                str.append(productName);

                                str.append("\nNumber of items: ");

                                str.append(quantityPurchased);

                                str.append("\nPrice Per Item: ");

                                str.append(cf.format(pricePerItem));

                                str.append("\nTotal cost: ");

                                str.append(cf.format(getTotalCost()));

                                return str.toString();

                }

}

// Invoice_Main.java

import java.util.Scanner;

public class Invoice_Main {

                public static void main(String[] args) {

                                new Invoice_GUI();

                                /*

                                * The below codes are unnecessary for this program, Scanner sc = new

                                * Scanner(System.in);

                                *

                                * System.out.println("Enter the name of the Product");

                                *

                                * invoice.setProductName(sc.nextLine());

                                *

                                * System.out.println("Enter the Quantity Purchased");

                                *

                                * invoice.setQuantityPurchased(sc.nextInt());

                                *

                                * System.out.println("Enter the price of the item");

                                *

                                * invoice.setPricePerItem(sc.nextDouble());

                                *

                                * System.out.println("\nProduct Purchased : " +

                                * invoice.getProductName());

                                *

                                * System.out.println("Total Cost : " + invoice.invoiceAmount());

                                */

                }

}

/*OUTPUT*/

Week 2 Practice Program--Invoice Product Name Mobile Phone 3 Item cost (10 to 10000) 299 Invoice Information: Product Name: Mobile Phone Total Cost Price Per Item: $299.00 Total cost: $897.00 Calculate total cost