rollingmessage.java

这是《Java 2 简明教程(第2版)》一书配套的源代码。

import java.applet.Applet;
import java.awt.Image;
import java.awt.Graphics;
import java.awt.Font;
import java.awt.Color;
import java.awt.*;

public class RollingMessage extends Applet implements Runnable
{
    Thread runThread;
    String s="Welcome to Tsinghua University!";
    int s_length=s.length();
    int x_character=0;
    Font wordFont=new Font("Arial",Font.BOLD,36);
    public void start()
    {
       if(runThread==null)
       {
          runThread=new Thread(this);
          runThread.start();
       }
    }
    public void stop()
    {
      if(runThread!=null)
      {
         runThread.stop();
         runThread=null;
      }
    }
    public void run()
    {
      while(true){
        if(x_character++>s_length)
           x_character=0;
      repaint(); 
      try{
         Thread.sleep(300);
      }
      catch(InterruptedException e) {}
    }
  }
    public void paint(Graphics g)
    {
      g.setFont(wordFont);
      g.setColor(Color.blue);
      g.drawString(s.substring(0,x_character),8,50);
    }
    public static void main(String args[])
    {
       Frame f=new Frame("DongHua Program");
       RollingMessage drawText=new RollingMessage();
       drawText.init();
       drawText.start();
       f.add("Center",drawText);
       f.setSize(400,100);
       f.show();
    }
}