Question

Java homework problem:

I need the code to be able to have a message if I type in a letter instead of a number. For example, " Please input only numbers". Then, I should be able to go back and type a number.

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.JPanel;
import javax.swing.JTextField;

public class LoginGui {
   static JFrame frame = new JFrame("JFrame Example");

   public static void main(String s[]) {
       JPanel panel = new JPanel();
       panel.setLayout(null);
       final JLabel label3 = new JLabel("Adult ticket $50.Children ticket $25");
       label3.setBounds(150, 15, 500, 30);
       JLabel label1 = new JLabel("Enter the number of adult ticket: ");
       label1.setBounds(200, 50, 300, 30);

       final JTextField adult = new JTextField(10);
       adult.setBounds(400, 50, 100, 30);

       JLabel label2 = new JLabel("Enter the number of children ticket: ");
       label2.setBounds(200, 100, 250, 30);
       // password field
       final JTextField children = new JTextField(10);
       children.setBounds(400, 100, 100, 30);

       JButton login = new JButton();
       login.setText("Calculate total cost");
       login.setBounds(200, 150, 250, 20);

       JLabel total = new JLabel("Total Price: ");
       total.setBounds(200, 200, 300, 30);

       final JTextField totalPrice = new JTextField(10);
       totalPrice.setBounds(400, 200, 100, 30);
       totalPrice.setEditable(false);

       JButton exit = new JButton();
       exit.setText("Exit");
       exit.setBounds(320, 150, 100, 20);

      

       login.addActionListener(new ActionListener() {

           @Override
           public void actionPerformed(ActionEvent aE) {
               String a = adult.getText();
               String c = children.getText();
               int ad = 0;
               if (a.trim().length() != 0)
                   ad = Integer.parseInt(a);
               int ac = 0;
               if (c.trim().length() != 0)
                   ac = Integer.parseInt(c);
               totalPrice.setText((ac * 25 + ad * 50) + "");

           }
       });

       panel.add(label1);
       panel.add(label2);
       panel.add(label3);
       panel.add(adult);
       panel.add(children);
       panel.add(login);
       panel.add(exit);
       panel.add(totalPrice);
       panel.add(total);
       frame.add(panel);

       frame.setSize(600, 300);
       frame.setLocationRelativeTo(null);
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
       frame.setVisible(true);
   }
}

Answer 1

import java.awt.Color;
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.JPanel;
import javax.swing.JTextField;

public class LoginGui {
static JFrame frame = new JFrame("JFrame Example");
static JLabel error = new JLabel("");
public static void main(String s[]) {
JPanel panel = new JPanel();
panel.setLayout(null);
final JLabel label3 = new JLabel("Adult ticket $50.Children ticket $25");
label3.setBounds(150, 15, 500, 30);
JLabel label1 = new JLabel("Enter the number of adult ticket: ");
label1.setBounds(200, 50, 300, 30);

final JTextField adult = new JTextField(10);
adult.setBounds(400, 50, 100, 30);

JLabel label2 = new JLabel("Enter the number of children ticket: ");
label2.setBounds(200, 100, 250, 30);
// password field
final JTextField children = new JTextField(10);
children.setBounds(400, 100, 100, 30);

JButton login = new JButton();
login.setText("Calculate total cost");
login.setBounds(200, 250, 250, 20);

JLabel total = new JLabel("Total Price: ");
total.setBounds(200, 150, 300, 30);
error.setBounds(250, 200, 300, 30);
error.setForeground(Color.red);

final JTextField totalPrice = new JTextField(10);
totalPrice.setBounds(400, 150, 100, 30);
totalPrice.setEditable(false);

JButton exit = new JButton();
exit.setText("Exit");
exit.setBounds(320, 250, 100, 20);

  

login.addActionListener(new ActionListener() {

@Override
public void actionPerformed(ActionEvent aE) {
String a = adult.getText();
String c = children.getText();
error.setText("");
int ad = 0;
try {
if (a.trim().length() != 0)
ad = Integer.parseInt(a);
int ac = 0;
if (c.trim().length() != 0)
ac = Integer.parseInt(c);
totalPrice.setText((ac * 25 + ad * 50) + "");
}catch(Exception e) {
   error.setText("Please enter numbers only: ");
}

}
});

panel.add(label1);
panel.add(error);

panel.add(label2);
panel.add(label3);
panel.add(adult);
panel.add(children);
panel.add(login);
panel.add(exit);
panel.add(totalPrice);
panel.add(total);
frame.add(panel);

frame.setSize(600, 400);
frame.setLocationRelativeTo(null);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
}

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