complete11_5.java

程序练习中包括书中实例程序代码和练习中要用到的代码,是压缩文件

package questions.c11;
import java.awt.*;
import java.awt.event.*;

public class Complete11_5 extends Frame {
   private BallPanel redPanel;
   private BallPanel greenPanel;
   private BallPanel bluePanel;
   Complete11_5( String title ) {
      super( title );
      setLayout( new GridLayout( 3, 1 ) ); 
      redPanel = new BallPanel( Color.red );
      add( redPanel );
      greenPanel = new BallPanel( Color.green );
      add( greenPanel );
      bluePanel = new BallPanel( Color.blue );
      add( bluePanel );
      addWindowListener( new WindowAdapter () {
            public void windowClosing( WindowEvent event ) {
               dispose(); 
               System.exit( 0 );
            } 
         }
      );
      pack();
      setVisible( true );
  }
  public static void main( String[] args ) { 
     Complete11_5 area = new Complete11_5( " Moving Ball" );
     area.redPanel.dropBall();
     area.greenPanel.dropBall();
     area.bluePanel.dropBall();
   }
}

class BallPanel extends Panel implements Runnable {
   private int x = 0, y = 20;
   private Thread ballThread;
   BallPanel( Color foreground ) {
      setForeground( foreground );
      setSize( 400, 60 );
      setLayout( null );
   }
   void dropBall() {
      ballThread = new Thread( this );
      ballThread.start();
   }
   public void paint( Graphics g ) {
      g.fillArc( x, y, 20, 20, 0, 360 ); 
   }
   public void update( Graphics g ) {
      g.fillArc( x, y, 20, 20, 0, 360 ); 
   }
   public void run() {
      while ( x < (int) (getSize().getWidth() ) ) {
         x += 20;
         repaint();
         // your code goes here
      }
   }
}