Program to explain Dialog class in Java

//  Program to explain Dialog class.
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
class MyDialog extends Dialog implements ActionListener
{
  Button b1;
  Label l1;
  
  MyDialog( Frame f, String s, boolean u )
  {
 super( f, s, u );
 setLayout( new FlowLayout() );
 b1 = new Button( "OK" );
 l1 = new Label();
 
 add( l1 );
 add( b1 );
 
 b1.addActionListener( this );
   }
   public void actionPerformed( ActionEvent e )
   {
 if( e.getSource() == b1 )
 {
  this.setVisible( false );
 }
}
}
class MyFrame extends Frame implements ActionListener
{
  Button b1;
  TextField t1;
  MyDialog d;
  String s1, s2;
  MyFrame()
  {
 super( " DIALOG DEMO " );
 d = new MyDialog( this, "Dialog Box", true );
 d.setSize( 200, 100 );
 d.setLocation( 300, 200 );
 setLayout( new FlowLayout() );
 
 Label l1 = new Label("Enter String: ");
 b1 = new Button( " REVERSE " );
 t1 = new TextField( 20 );
 add( l1 );
 add( t1 );
 add( b1 );  
     
 b1.addActionListener( this );
   }
   public void actionPerformed( ActionEvent e )
   {
 if( e.getSource() == b1 )
 {
  s1 = t1.getText();
  StringBuffer s = new StringBuffer( s1 );
  s2 = new String( s.reverse() );
  d.l1.setText( "Reversed String : " + s2 );
  d.l1.setVisible( true );
  d.setVisible( true );
 }
}
}
class DialogTest
{
  public static void main( String args[] )
  {
 MyFrame f = new MyFrame();
 f.setSize( 250, 200 );
 f.setLocation(300, 200);
 f.setBackground( Color.cyan );
 f.setVisible(true);
 
 f.addWindowListener( new WindowAdapter()
 {
  public void windowClosing( WindowEvent e )
  { 
   System.exit( 0 );
  }
 } );
  }
}