Java編程——數字時鍾

//ClockDemo.java

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

//數字時鍾
public class ClockDemo extends JFrame implements Runnable{
Thread clock;    

public ClockDemo(){
super("數字時鍾");    //調用父類構造函數    
setFont(new Font("Times New Roman",Font.BOLD,60));    //設置時鍾的顯示字體
start(); //開始進程
setSize(280,100); //設置窗口尺寸
setVisible(true); //窗口可視
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //關閉窗口時退出程序
}

public void start(){ //開始進程
if (clock==null){ //如果進程為空值
clock=new Thread(this); //實例化進程
clock.start(); //開始進程
}
}

public void run(){ //運行進程
while (clock!=null){ 
repaint(); //調用paint方法重繪界面
try{
Thread.sleep(1000); //線程暫停一秒(1000毫秒)
}
catch (InterruptedException ex){
ex.printStackTrace(); //輸出出錯信息
}
}    
}

public void stop(){ //停止進程
clock=null;
}

public void paint(Graphics g){ //重載組件的paint方法
Graphics2D g2=(Graphics2D)g; //得到Graphics2D對象
Calendar now=new GregorianCalendar(); //實例化日歷對象
String timeInfo=""; //輸出信息
int hour=now.get(Calendar.HOUR_OF_DAY); //得到小時數
int minute=now.get(Calendar.MINUTE); //得到分數
int second=now.get(Calendar.SECOND); //得到秒數

if (hour<=9) 
timeInfo+="0"+hour+":"; //格式化輸出
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); //設置當前顏色為白色
Dimension dim=getSize(); //得到窗口尺寸
g.fillRect(0,0,dim.width,dim.height); //填充背景色為白色
g.setColor(Color.orange); //設置當前顏色為橙色
g.drawString(timeInfo,20,80); //顯示時間字符串
}

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