How to add buttons and panels in frame in java?

How would you change the program below so that it would work right?

• Does anybody know what class is MessagePanel-class? It does not appear in the http://docs.oracle.com/javase/6/docs/api/ or even 7 version. How would you change the program below so that it would work right? import java.awt.*; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import javax.swing.*; public class ButtonDemo extends JFrame { // Create a panel for displaying message protected MessagePanel messagePanel = new MessagePanel("Welcome to Java"); // Declare two buttons to move the message left and right private JButton jbtLeft = new JButton("<="); private JButton jbtRight = new JButton("=>"); public static void main(String[] args) { ButtonDemo frame = new ButtonDemo(); frame.setTitle("ButtonDemo"); frame.setLocationRelativeTo(null); // Center the frame frame.setDefaultCloseOperation(JFrame.… frame.setSize(250, 100); frame.setVisible(true); } public ButtonDemo() { // Set the background color of messagePanel messagePanel.setBackground(Color.white… // Create Panel jpButtons to hold two Buttons "<=" and "right =>" JPanel jpButtons = new JPanel(); jpButtons.add(jbtLeft); jpButtons.add(jbtRight); // Set keyboard mnemonics jbtLeft.setMnemonic('L'); jbtRight.setMnemonic('R'); // Set icons and remove text // jbtLeft.setIcon(new ImageIcon("image/left.gif")); // jbtRight.setIcon(new ImageIcon("image/right.gif")); // jbtLeft.setText(null); // jbtRight.setText(null); // Set tool tip text on the buttons jbtLeft.setToolTipText("Move message to left"); jbtRight.setToolTipText("Move message to right"); // Place panels in the frame setLayout(new BorderLayout()); add(messagePanel, BorderLayout.CENTER); add(jpButtons, BorderLayout.SOUTH); // Register listeners with the buttons jbtLeft.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { messagePanel.moveLeft(); } }); jbtRight.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { messagePanel.moveRight(); } }); } }

• Answer:

  MessagePanel is a custom class defined in Chapter 15. Put the code for the MessagePanel class in the same package as ButtonDemo, and it should compile fine.