Solutions to the Try It Out Exercises in Beginning Programming with Java For Dummies, 6th Edition
by Barry Burd

Chapter 20: Oooey GUI Was a Worm

In this chapter:

• Mix it up
• Copy text to a text field
• Copy text to a label
• Copy between text fields
• Create a small calculator

Mix it up

• In the main method, a variable must be declared before it's used.
• You must add everything that you're going to add to the frame before you call the frame's pack method.

// Bad code:
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JFrame frame = new JFrame();

// Bad code:
frame.pack();
frame.add(label);

Copy text to a text field

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class CopyFieldToField {
    public CopyFieldToField() {
        copyButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textField2.setText(textField1.getText());
            }
        });
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("CopyFieldToField");
        frame.setContentPane(new CopyFieldToField().jPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200, 200);
        frame.setVisible(true);
    }

    private JPanel jPanel;
    private JTextField textField1;
    private JButton copyButton;
    private JTextField textField2;
}    

Copy text to a label

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

public class CopyFieldToLabel {
    public CopyFieldToLabel() {
        copyButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                jLabel.setText(textField1.getText());
            }
        });
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("CopyFieldToLabel");
        frame.setContentPane(new CopyFieldToLabel().jPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200,200);
        frame.setVisible(true);
    }

    private JPanel jPanel;
    private JTextField textField1;
    private JButton copyButton;
    private JLabel jLabel;
}

Copy between text fields

  
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class CopyBetweenFields {
    private JPanel jpanel;

    public CopyBetweenFields() {
        a1stTo2ndButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textField2.setText(textField1.getText());
            }
        });
        a2ndTo1stButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                textField1.setText(textField2.getText());
            }
        });
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("CopyBetweenFields");
        frame.setContentPane(new CopyBetweenFields().jpanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(200,200);
        frame.setVisible(true);
    }

    private JTextField textField1;
    private JButton a1stTo2ndButton;
    private JButton a2ndTo1stButton;
    private JTextField textField2;
}

Create a small calculator

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

public class Calculator {
    private JPanel jPanel;

    public Calculator() {
        addButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                int number1 = Integer.parseInt(textField1.getText());
                int number2 = Integer.parseInt(textField2.getText());
                jLabel.setText(Integer.toString(number1 + number2));
            }
        });
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Calculator");
        frame.setContentPane(new Calculator().jPanel);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);
        frame.setVisible(true);
    }

    private JTextField textField1;
    private JTextField textField2;
    private JButton addButton;
    private JLabel jLabel;
}