最近在学习JAVA线程，照着书上例子写的钟表图形程序，对线程有一定的理解，但是发觉对图形编程的掌握不够很多函数还不能掌握~~

以下是钟表例子的代码

 package hello; 
 import java.awt.*;
 import java.applet.*;
 import java.awt.event.*;
 import java.util.*;
 import java.awt.geom.*;

public class T extends Applet implements Runnable{
  Thread tHour = null,tMinute = null,tSecond = null;//表示时针，分针和秒针的线程
  int hour_a,hour_b,minute_a,minute_b,second_a,second_b;//表示时针，分针，秒针端点的整型变量
  int hour = 0,minute = 0,second = 0;//获取当前时间的整型变量
 
  //绘制时针，分针和秒针的Graphics对象
  Graphics g_second = null,g_minute = null,g_hour =null;
  //存放表盘刻度的数组，供指针走动时使用
  double  point_x[] = new double[61],point_y[] = new double[61];
  //存放表盘刻度的数组，供绘制表盘使用
  double scaled_x[] = new double[61],scaled_y[] = new double[61];
  //判断小程序是否重新开始的变量
  int start_count = 0;
 
  public void init(){
   g_hour = this.getGraphics();
   g_hour.setColor(Color.CYAN);
   g_second = this.getGraphics();
   g_second.setColor(Color.RED);
   g_minute = this.getGraphics();
   g_minute.setColor(Color.blue);
   g_second.translate(200,200);//进行坐标系统变换，将新坐标系原点设在（200，200）处
   g_minute.translate(200,200);
   g_hour.translate(200,200);
   point_x[0] = 0; point_y[0] = -120;//各个时针12点处的位置坐标（按新坐标系的坐标）
   scaled_x[0] = 0;scaled_y[0] = -140;//12点处的刻度位置坐标（按新坐标系的坐标）
   double jiaodu = 6*Math.PI/180;
   //表盘分割成60分，将分割点的坐标存放在数组中
   for(int i = 0; i < 60; i++){
    point_x[i+1] = point_x[i]*Math.cos(jiaodu)-Math.sin(jiaodu)*point_y[i];
    point_y[i+1] = point_y[i]*Math.cos(jiaodu) + point_x[i]*Math.sin(jiaodu);   
   }
   
   point_x[60] = 0; point_y[60] = -120;
   
   for(int i = 0; i < 60; i++){
    scaled_x[i+1] = scaled_x[i]*Math.cos(jiaodu)-Math.sin(jiaodu)*scaled_y[i];
    scaled_y[i+1] = scaled_y[i]*Math.cos(jiaodu) + Math.sin(jiaodu)*scaled_x[i];
   }
   scaled_x[60]= 0;
   scaled_y[60] = -140;
  }
  public void start(){
   //每当小程序重新开始时，首先消灭线程，然后重新开始创建线程
   if(start_count >= 1){
    tSecond.interrupt();
    tMinute.interrupt();
    tHour.interrupt();
   }
   tSecond = new Thread(this);
   tMinute = new Thread(this);
        tHour   = new Thread(this);
        tSecond.start();
        tMinute.start();
        tHour.start();
        start_count++;
        if(start_count >= 2) start_count = 1;
  }
 
  public void stop()
  {
   tSecond.interrupt();
   tMinute.interrupt();
   tHour.interrupt();
  }
 
  public void paint(Graphics g){
   this.start();
   g.drawOval(50,50,300,300);//表盘的外圈
   g.translate(200,200);
   //绘制表盘的小刻度和大刻度
   for(int i = 0 ; i < 60; i++){
    if(i%5 == 0){
     g.setColor(Color.BLACK);
     g.fillOval((int) scaled_x[i],(int) scaled_y[i],10,10);
    }
    else
     g.fillOval((int)scaled_x[i],(int)scaled_y[i],5,5);
   }
  }
  public void run(){
   //获取本地时间
   Date date = new Date();
   String s=date.toString();
   hour=Integer.parseInt(s.substring(11,13));
   minute = Integer.parseInt(s.substring(14,16));
   second = Integer.parseInt(s.substring(17,19));
   if(Thread.currentThread() == tSecond){
    second_a =(int)point_x[second];
    second_b = (int)point_x[second];
    g_second.drawLine(0,0,second_a,second_b);//秒针的初始位置
    g_second.drawString("秒",second_a,second_b);
    int i = second;
    while(true){
     try{
      tSecond.sleep(1000);
      Color c = getBackground();
      g_second.setColor(c);
      g_second.drawLine(0,0,second_a,second_b);//用背景色清除前一秒时的秒针
      g_second.drawString("秒",second_a,second_b);
      //如果秒针与分针重合，恢复分针的显示
      if((second_a == minute_a)&&(second_b == minute_b)){
       g_minute.drawLine(0,0,minute_a,minute_b);
       g_minute.drawString("分",minute_a,minute_b);
      }
      //如果秒针与时针重合，恢复时针的显示
      if((second_a == hour_a)&&(second_b == hour_b)){
       g_hour.drawLine(0,0,hour_a,hour_b);
       g_hour.drawString("时",hour_a,hour_b);
      }
     }
     catch(InterruptedException e){
      Color c = getBackground();
      g_second.setColor(c);
      g_second.drawLine(0,0,second_a,second_b);//用背景色清除秒针
      g_second.drawString("秒",second_a,second_b);
      return;
     }
     //秒针向前走一个单位
     second_a=(int)point_x[(i+1)%60];
     second_b = (int)point_y[(i+1)%60]; //每一秒走6度（一个单位格）
     g_second.setColor(Color.red);
     g_second.drawLine(0,0,second_a,second_b);
     g_second.drawString("秒",second_a,second_b);
     i++;
    }
   }
   if(Thread.currentThread() == tMinute){
    minute_a = (int)point_x[minute];
    minute_b = (int)point_y[minute];
    g_minute.drawLine(0,0,minute_a,minute_b);
    int i = minute;
    while(true){
     //第一次过60-second秒就前进一分钟，以后每过60秒前进一分钟
     try{
      tMinute.sleep(1000*60 - second*1000);
      second = 0;
      Color c = getBackground();
      g_minute.setColor(c);
      
      g_minute.drawLine(0,0,minute_a,minute_b);
      g_minute.drawString("分",minute_a,minute_b);
      
      if((hour_a == minute_a)&&(hour_b== minute_b)){
       g_hour.drawLine(0,0,minute_a,minute_b);
       g_hour.drawString("时",hour_a,hour_b);
      }   
     }
     catch(InterruptedException e){
      return;
     }
     minute_a = (int)point_x[(i+1)%60];
     minute_b = (int)point_y[(i+1)%60];
     g_minute.setColor(Color.BLUE);
     g_minute.drawLine(0,0,minute_a,minute_b);
     g_minute.drawString("分",minute_a,minute_b);
     i++; second = 0;
    }    
   }
   
   if(Thread.currentThread() == tHour){
    int h = hour%12;
    hour_a = (int)point_x[h*5 + minute/12];
    hour_b = (int)point_y[h*5 + minute/12];
    int i = h*5 + minute/12;
    g_hour.drawLine(0,0,hour_a,hour_b);
    g_hour.drawString("时",hour_a,hour_b);
    while(true){
     //第一次过12-minute%12分钟就前进一个刻度，以后每过12分钟前进一个刻度
     try{
      tHour.sleep(1000*60*12 - 1000*60*(minute%12) - second *1000);
      minute = 0;
      Color c = getBackground();
      g_hour.setColor(c);
      g_hour.drawLine(0,0,hour_a,hour_b);
      g_hour.drawString("时",hour_a,hour_b);
     }
     catch(InterruptedException e){
      return;
     }
     hour_a = (int)point_x[(i+1)%60];
     hour_b = (int)point_y[(i+1)%60];
     g_hour.setColor(Color.CYAN);
     g_hour.drawLine(0,0,hour_a,hour_b);
     g_hour.drawString("时",hour_a,hour_b);
     i++;minute = 0;
    }
   }
  }
}