Description
Part 1: Compile and Run a Java Console Program
Type in (or copy and paste) the program listed below and save it as Add1.java. The file name is case-sensitive and must match the class name in the program below.
import java.util.Scanner;
/*
* Add1.java
*
* Console program to add two numbers.
*/
public class Add1 {
public static void main(String[] args) {
String amountStr;
double num1, num2;
Scanner sc = new Scanner(System.in);
// Read the first number as a String.
System.out.println(“Enter the first number: “);
amountStr = sc.next();
// Try to convert String to double for calculation.
try {
num1 = Double.parseDouble(amountStr);
}
catch (NumberFormatException nfe) {
System.out.println(“1st number invalid.”);
return;
}
// Read the second number as a String.
System.out.println(“Enter the second number: “);
amountStr = sc.next();
// Try to convert String to double for calculation.
try {
num2 = Double.parseDouble(amountStr);
}
catch (NumberFormatException nfe) {
System.out.println(“2nd number invalid.”);
return;
}
// Compute and print the sum.
System.out.printf(“Sum is: %.2f\n”, num1 + num2);
}
}
Part 2: Build and Run a Java Swing GUI Program
Type in (or copy and paste) the following program, and then build and run it.
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
/*
* Add2
*
* Swing program to find the sum of two numbers.
*/
public class Add2 extends JFrame implements ActionListener {
private static final long serialVersionUID = 1L;
private JButton addButton = new JButton(“Add Numbers”);
private JButton clearButton = new JButton(“Clear Numbers”);
private JTextField num1Field = new JTextField(10);
private JTextField num2Field = new JTextField(10);
private JLabel sumLabel = new JLabel();
public static void main(String[] args) {
EventQueue.invokeLater(() -> {
Add2 frame = new Add2(“Sum of Two Numbers”);
frame.createAndShowGUI();
});
}
private Add2(String title) {
super(title);
}
/*
* Create the GUI and show it. For thread safety, this method should
* be invoked from the event-dispatch thread.
*/
private void createAndShowGUI() {
initComponents();
// Add listeners for the buttons.
addButton.addActionListener(this);
clearButton.addActionListener(this);
// Display the window.
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
pack();
setVisible(true);
}
/*
* Set the frame’s layout, create the UI components, and add them to the
* layout.
*/
private void initComponents() {
JPanel panel = new JPanel(new GridLayout(4, 2, 5, 5));
panel.setBorder(BorderFactory.createEmptyBorder(10, 10, 10, 10));
panel.add(new JLabel(“First number:”));
panel.add(num1Field);
panel.add(new JLabel(“Second number:”));
panel.add(num2Field);
panel.add(new JLabel(“Sum:”));
panel.add(sumLabel);
panel.add(addButton);
panel.add(clearButton);
add(panel, BorderLayout.CENTER);
}
/*
* Handle ActionEvents from the buttons.
*/
@Override
public void actionPerformed(ActionEvent e) {
double num1, num2;
if (e.getSource() == clearButton) {
num1Field.setText(“”);
num2Field.setText(“”);
sumLabel.setText(“”);
}
else {
// Try to convert String to double for calculation
try {
num1 = Double.parseDouble(num1Field.getText());
}
catch (NumberFormatException nfe) {
sumLabel.setText(“1st number invalid.”);
return;
}
// Try to convert String to double for calculation
try {
num2 = Double.parseDouble(num2Field.getText());
}
catch (NumberFormatException nfe) {
sumLabel.setText(“2nd number invalid.”);
return;
}
// Compute and display the sum.
sumLabel.setText(String.format(“%.2f”, num1 + num2));
}
}
}
