/* * This is a 1.3 version (thanks to JFrame.EXIT_ON_CLOSE) * but could easily be converted to work in earlier releases. * There are many valid ways to implement the exercise. */ import javax.swing.*; import java.awt.*; import java.awt.event.*; public class SwingApp2 { JButton startButton, stopButton; JLabel label; public SwingApp2() { JFrame f = new JFrame("SwingApp2"); f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //1.3+ createGUI(f); initListeners(); f.pack(); f.setVisible(true); } void initListeners() { ActionListener al = new MyActionListener(); startButton.addActionListener(al); stopButton.addActionListener(al); } class MyActionListener implements ActionListener { public void actionPerformed(ActionEvent e) { if (e.getSource() == startButton) { startButton.setEnabled(false); stopButton.setEnabled(true); label.setText("Press Stop."); } else { // e.getSource() == stopButton stopButton.setEnabled(false); startButton.setEnabled(true); label.setText("Press Start."); } } } void createGUI(JFrame f) { startButton = new JButton("Start"); stopButton = new JButton("Stop"); stopButton.setEnabled(false); label = new JLabel("Press Start.", JLabel.CENTER); Container c = f.getContentPane(); //Use the content pane's default BorderLayout layout manager. c.add(startButton, BorderLayout.WEST); c.add(stopButton, BorderLayout.EAST); c.add(label, BorderLayout.SOUTH); } public static void main(String[] args) { new SwingApp2(); } }