效果：

代码实现：

package Clock2;

import java.awt.*;

import java.text.DateFormat;

import java.util.*;

import javax.swing.*;

//数字时钟

public class ClockDemo extends JFrame implements Runnable{

private static final long serialVersionUID = 1L;

Thread clock;

final int Xpoint=180;

final int Ypoint=180;

final int R=80;

int xHour=0,yHour=0,xSecond=0,ySecond=0,xMin=0,yMin=0;

public ClockDemo()

{

super("数字时钟"); //调用父类构造函数

setFont(new Font("宋体",Font.BOLD,20)); //设置时钟的显示字体

start(); //开始进程

setSize(400,400);  //设置窗口尺寸

setVisible(true);  //窗口可视

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);  //关闭窗口时退出程序

}

public void start()

{ //开始进程

if(clock==null)//如果进程为空值

{

clock=new Thread(this); //实例化进程

clock.start(); //开始进程

}

}

public void run()//运行进程

{

while (clock!=null)

{

repaint(); //调用paint方法重绘界面

try

{

Thread.sleep(1000);  //线程暂停一秒(1000毫秒)

}

catch (InterruptedException ex){

ex.printStackTrace();  //输出出错信息

}}}

public void stop(){ //停止进程

clock=null;

}

public void paint(Graphics g) {//重载组件的paint方法

//Graphics2D g2=(Graphics2D)g;  //得到Graphics2D对象

DateFormat dateFormat = DateFormat.getDateInstance(DateFormat.FULL);

Calendar now=new GregorianCalendar(); //实例化日历对象

now.setTime(new Date());//dateFormat.format(now.getTime())

String timeInfo=""; //输出信息

int hour=now.get(Calendar.HOUR_OF_DAY); //得到小时数

int minute=now.get(Calendar.MINUTE);   //得到分数

int second=now.get(Calendar.SECOND);  //得到秒数

if (hour<=9)

timeInfo+="0"+hour+":"; //格式化输出

else

timeInfo+=hour+":";

if (minute<=9)

timeInfo+="0"+minute+":";

else

timeInfo+=minute+":";

if (second<=9)

timeInfo+="0"+second;

else

timeInfo+=second;

g.setColor(Color.yellow);  //设置当前颜色为白色

Dimension dim=getSize();  //得到窗口尺寸

g.fillRect(0,0,dim.width,dim.height);  //填充背景色为白色

g.setColor(Color.red);  //设置当前颜色为橙色

g.drawString(timeInfo,130,340);  //显示时间字符串

g.setColor(Color.green);

g.drawString(dateFormat.format(now.getTime()),20,60);

g.setColor(Color.black);

g.setFont(new Font("SAN_SERIF",Font.BOLD,15));

for(int i=0,num=12;i<360;i+=6)

{

double alfa = Math.toRadians(i);

int xPos=Xpoint+(int)(R*Math.sin(alfa));

int yPos=Ypoint-(int)(R*Math.cos(alfa));

if(i==0)

{

if (num%3==0)

g.setColor(Color.red);  //  数字3,6,9,12为红色

else

g.setColor(Color.black);  // 其余数字为黑色

g.drawString(""+num,xPos-5,yPos+3);  // 写数字

num=(num+1);

}

else

{

g.setColor(Color.black);

g.drawString(".",xPos,yPos);

}

}

g.setColor(Color.black);

g.fillOval(Xpoint-4,Ypoint-4,10,10);

//画秒针

xSecond=(int)(Xpoint+(R-10)*Math.sin(second*(2*Math.PI/60)));

ySecond=(int)(Ypoint-(R-10)*Math.cos(second*(2*Math.PI/60)));

g.setColor(Color.black);

g.drawLine(Xpoint,Ypoint,xSecond,ySecond);

//画分针

xMin=(int)(Xpoint+(R-20)*Math.sin((minute+second/60)*(2*Math.PI/60)));

yMin=(int)(Ypoint-(R-20)*Math.cos((minute+second/60)*(2*Math.PI/60)));

g.setColor(Color.red);

g.drawLine(Xpoint,Ypoint,xMin,yMin);

//画时针

xHour=(int)(Xpoint+(R-30)*Math.sin((hour+minute/60+second/60/60)*(2*Math.PI/12)));

yHour=(int)(Ypoint-(R-30)*Math.cos((hour+minute/60+second/60/60)*(2*Math.PI/12)));

g.setColor(Color.red);

g.drawLine(Xpoint,Ypoint,xHour,yHour);

}

public static void main(String[] args)

{

new ClockDemo();}}