// Fig. 13.6: DrawShapes.java Draw random lines, rectangles and ovals
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class DrawShapesApplet extends JApplet {
   private JButton choices[];
   private String names[] = { "Line", "Rectangle", "Oval" };
   private JPanel buttonPanel;
   private DrawPanel drawingArea;
   private int width = 300, height = 200;
   public void init()
   {
      drawingArea = new DrawPanel( width, height );
      choices = new JButton[ names.length ];
      buttonPanel = new JPanel();
      buttonPanel.setLayout(
         new GridLayout( 1, choices.length ) );
      ButtonHandler handler = new ButtonHandler();

      for ( int i = 0; i < choices.length; i++ ) {
         choices[ i ] = new JButton( names[ i ] );
         buttonPanel.add( choices[ i ] );
         choices[ i ].addActionListener( handler );
      }

      Container c = getContentPane();
      c.add( buttonPanel, BorderLayout.NORTH );
      c.add( drawingArea, BorderLayout.CENTER );
   }

   private class ButtonHandler implements ActionListener {
      public void actionPerformed( ActionEvent e )
      {
         for ( int i = 0; i < choices.length; i++ )
            if ( e.getSource() == choices[ i ] ) {
               drawingArea.setCurrentChoice( i );
               break;
            }
      }
   }
}
// subclass of JPanel to allow drawing in a separate area
class DrawPanel extends JPanel {
   private int currentChoice = -1;  // don't draw first time
   private int width = 100, height = 100;

   public DrawPanel( int w, int h )
   {
      width = ( w >= 0 ? w : 100 );
      height = ( h >= 0 ? h : 100 );
   }
   public void paintComponent( Graphics g )
   {
      super.paintComponent( g );
      switch( currentChoice ) {
         case 0:
            g.drawLine( randomX(), randomY(),randomX(), randomY() );
            break;
         case 1:
            g.drawRect( randomX(), randomY(),randomX(), randomY() );
            break;
         case 2:
            g.drawOval( randomX(), randomY(),randomX(), randomY() );
            break;
      }
   }
   public void setCurrentChoice( int c )
   {
      currentChoice = c;
      repaint();
   }
   private int randomX()
      { return (int) ( Math.random() * width ); }
   private int randomY()
      { return (int) ( Math.random() * height ); }
}