IOapalooza5.java

/*
    IOapalooza5.java
    CIS 260
    David Klick
    2006-01-18

This program demonstrates how to do I/O using a basic, but
    complete GUI.
*/

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class IOapalooza5 {
    public static void main(String[] args) {
        JFrame fra = new JFrame("Adding Application");
        fra.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Container c = fra.getContentPane();
        c.setLayout(new GridLayout(2, 2, 2, 5));
        final JTextField txt = new JTextField();
        txt.addFocusListener(new FocusListener() {
            public void focusGained(FocusEvent e) {
                txt.setSelectionStart(0);
                txt.setSelectionEnd(txt.getText().length());
            }
            public void focusLost(FocusEvent e) {}
        });

final JLabel lbl = new JLabel();
 JButton btnAdd = new JButton("<html>Add</html>");
 btnAdd.setMnemonic('a');
 btnAdd.addActionListener(new ActionListener() {
 public void actionPerformed(ActionEvent e) {
 double sum = 0.0, num = 0.0;
 String strSum = lbl.getText();
 if (strSum.length() > 0) sum = Double.parseDouble(strSum);
 try {
 String strNum = txt.getText();
 num = Double.parseDouble(strNum);
 sum += num;
 txt.setText("");
 } catch (NumberFormatException e2) {
 txt.setSelectionStart(0);
 txt.setSelectionEnd(txt.getText().length());
 }
 lbl.setText("" + sum);
 txt.requestFocusInWindow();
 }
 });
 fra.getRootPane().setDefaultButton(btnAdd);

JButton btnExit = new JButton("Exit");
        btnExit.setMnemonic('x');
        btnExit.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                System.exit(0);
            }
        });
        c.add(txt);
        c.add(lbl);
        c.add(btnAdd);
        c.add(btnExit);
        fra.setSize(200, 110);
        fra.setVisible(true);
    }
}