libraryclock.java

这是一个简单的图书管理系统,适用于教学中演示,讲解java高级编程语言

package lib_source;
import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.*;
import javax.swing.*;
public class LibraryClock extends JFrame implements Runnable{
	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;
	Thread clock;	
	public LibraryClock(){
		super("系统时钟");
	setResizable(false);
		start(); 
		setFont(new Font("Times New Roman",Font.BOLD,60));	//设置时钟的显示字体
		setSize(280,100);  //设置窗口尺寸
		setVisible(true);  
		setDefaultCloseOperation(WindowConstants.DO_NOTHING_ON_CLOSE);
		addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				dispose();
			}
		});
		Dimension screen = getToolkit().getScreenSize();
		
		setLocation((screen.width - getSize().width) / 2,
				(screen.height - getSize().height) / 2);
	}
	public void start(){ 
		if (clock==null){ 
			clock=new Thread(this); 
			clock.start(); 
		}
	}
	public void run(){  
		while (clock!=null){ 
		repaint();
			try{
				Thread.sleep(1000); 
			}
			catch (InterruptedException ex){
				JOptionPane.showMessageDialog(this,
				"多线程错误!");		
			}
		}	
	}
	public void stop(){  
		clock=null;
	}
	public void paint(Graphics g){  
	//	Graphics2D g2=(Graphics2D)g;  
		Calendar now=new GregorianCalendar();
		String timeInfo=""; 
		int hour=now.get(Calendar.HOUR_OF_DAY); 
		int minute=now.get(Calendar.MINUTE);   
		int second=now.get(Calendar.SECOND);  
		if (hour<=9) 
			timeInfo+="0"+hour+":";
		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 LibraryClock();
	}
}