Java编程——数字时钟

//ClockDemo.java

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package newpackage;
import java.awt.*;
import java.util.*;
import javax.swing.*;

//数字时钟
public class ClockDemo extends JFrame implements Runnable{
Thread clock;    

public ClockDemo(){
super("数字时钟");    //调用父类构造函数    
setFont(new Font("Times New Roman",Font.BOLD,60));    //设置时钟的显示字体
start(); //开始进程
setSize(280,100); //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
Calendar now=new GregorianCalendar(); //实例化日历对象
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.white); //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.orange); //设置当前颜色为橙色
g.drawString(timeInfo,20,80); //显示时间字符串
}

public static void main(String[] args){
new ClockDemo();
}
}