做一个时钟

import java.util.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.Timer;

public class Clock extends JFrame implements ActionListener
 {
 private static final long serialVersionUID = 6790815213225162093L;
 Timer timer;
    int x,y,old_X,old_Y, r,x0,y0,w,h,ang;
    int sdo,mdo,hdo,old_M,old_H;
    TimeZone tz =TimeZone.getTimeZone("JST");
    final double RAD=Math.PI/180.0;
   
public Clock()
  {
     super("时钟");
      setSize(300,300);
        setBackground(new Color(0,0,192));
        setResizable(false);   
        Dimension scr=Toolkit.getDefaultToolkit().getScreenSize();
        Dimension fra=this.getSize();
        if(fra.width>scr.width)
        {
            fra.width=scr.width;
        }
        if(fra.height>scr.height)
        {
            fra.height=scr.height;
        }
  this.setLocation((scr.width-fra.width)/2,(scr.height-fra.height)/2);
     setVisible(true);
     int delay = 1000; 
     ActionListener taskPerformer = new ActionListener()
     {
        public void actionPerformed(ActionEvent evt)
        {
           repaint();
        }
     };
     new Timer(delay, taskPerformer).start();
  }
 
  public void actionPerformed(ActionEvent e)
  {
        timer.restart();
  }

  public void paint( Graphics g )
  {
  Insets insets = getInsets();
      int L0 = (insets.left)/2, T0 = (insets.top)/2;
      int hh,mm,ss;
      String st;
      h=getSize().height;
      g.setColor(Color.white);
      g.drawOval(L0+30,T0+30,h-60,h-60);
      g.drawOval(L0+32,T0+32,h-64,h-64);
      r=h/2-30;
      x0=30+r-5+L0;
      y0=30+r-5-T0;
      ang=60;
      for (int i=1; i<=12; i++)
      {
         x=(int)((r+10)*Math.cos(RAD*ang)+x0);
         y=(int)((r+10)*Math.sin(RAD*ang)+y0);
         g.drawString(""+i,x,h-y);
         ang-=30;
      }
      x0=30+r+L0; y0=30+r+T0;
      Calendar now=Calendar.getInstance();
      hh=now.get(Calendar.HOUR_OF_DAY);
      mm=now.get(Calendar.MINUTE);
      ss=now.get(Calendar.SECOND);
      g.setColor(Color.pink);
      g.fillRect(L0,T0,60,28);
      g.setColor(Color.blue);
      if (hh < 10) st="0"+hh;     else st=""+hh;
      if (mm < 10) st=st+":0"+mm; else st=st+":"+mm;
      if (ss < 10) st=st+":0"+ss; else st=st+":"+ss;
      g.drawString(st,L0,T0+25);
      sdo=90-ss*6;
      mdo=90-mm*6;
      hdo=90-hh*30-mm/2;
      if (old_X > 0)
      {
         g.setColor(getBackground());
         g.drawLine(x0,y0,old_X,(h-old_Y));
      } else
      {
         old_M=mdo;
         old_H=hdo;
      }
      g.setColor(Color.yellow);
      x=(int)((r-8)*Math.cos(RAD*sdo)+x0);
      y=(int)((r-8)*Math.sin(RAD*sdo)+y0)-2*T0;
      g.drawLine(x0,y0,x,(h-y));
    
      old_X=x;
      old_Y=y;
      if (mdo != old_M)
      {
         line(g,old_M,(int)(r*0.7),getBackground());
         old_M=mdo;
      }
      if (hdo != old_H)
      {
         line(g,old_H,(int)(r*0.5),getBackground());
         old_H=hdo;
     }
      line(g,mdo,(int)(r*0.7),Color.green);
      line(g,hdo,(int)(r*0.5),Color.red);
  }

 public void line(Graphics g, int t, int n, Color c)
    {
  int [] xp = new int[4];
       int [] yp = new int[4];
       xp[0]=x0;
  yp[0]=y0;
       xp[1]=  (int)((n-10)*Math.cos(RAD*(t-4))+x0);
       yp[1]=h-(int)((n-10)*Math.sin(RAD*(t-4))+y0);
       xp[2]=  (int)( n    *Math.cos(RAD* t   )+x0);
       yp[2]=h-(int)( n    *Math.sin(RAD* t   )+y0);
       xp[3]=  (int)((n-10)*Math.cos(RAD*(t+4))+x0);
       yp[3]=h-(int)((n-10)*Math.sin(RAD*(t+4))+y0);
       g.setColor(c);
       g.fillPolygon(xp,yp,4);
   }
  
 public static void main(String args[])
    {
     new Clock();
    }
 }