import java.awt.BorderLayout ;
import java.awt.event.ActionEvent ;
import java.awt.event.ActionListener ;
import javax.swing.BorderFactory ;
import javax.swing.JButton ;
import javax.swing.JFrame ;
import javax.swing.JLabel ;
import javax.swing.JPanel ;
import javax.swing.SwingConstants ;
import javax.swing.SwingUtilities ;
public class HelloGoodbye extends JFrame {
  private static final String HELLO = "Hello!" ;
  private static final String GOODBYE = "Goodbye!" ;
  private String message = HELLO ;
  public HelloGoodbye ( ) {
    super ( "HelloGoodbye" ) ;
    final JLabel aLabel = new JLabel ( message , SwingConstants.CENTER ) ;
    final JButton aButton = new JButton ( "Click Me" ) ;
    aButton.addActionListener ( new ActionListener ( ) {
        public void actionPerformed ( final ActionEvent e ) {
          message = message.equals ( HELLO ) ? GOODBYE : HELLO ;
          aLabel.setText ( message ) ;
        }
      } ) ;
    final JPanel aPanel = new JPanel ( ) ;
    aPanel.setBorder ( BorderFactory.createEmptyBorder ( 20 , 60 , 20 , 60 ) ) ;
    aPanel.setLayout ( new BorderLayout ( ) ) ;
    aPanel.add ( aLabel , BorderLayout.CENTER ) ;
    aPanel.add ( aButton , BorderLayout.SOUTH ) ;
    add ( aPanel ) ;
    setDefaultCloseOperation ( JFrame.EXIT_ON_CLOSE ) ;
    pack ( ) ;
    setVisible ( true ) ;
  }
  public static void main ( final String[] args ) {
    SwingUtilities.invokeLater ( new Runnable ( ) {
        public void run ( ) { new HelloGoodbye ( ) ; }
      } ) ;
  }
}