编写程序显示一个时钟。示例输出如图所示。

代码：

package com.DisplayClock;

import javax.swing.*;

import java.awt.*;

import java.awt.geom.*;

public class DisplayClock{

Thread hourThread = null;//时针线程

Thread minuteThread = null; //分针线程

Thread secondThread = null;//秒针线程

int currentHour = 0;//获取当前时间中代表小时的数字值

int currentMinute = 0;//获取当前时间中代表分钟的数字值

int currentSecond = 0;//获取当前时间中代表秒数字值

int isRestart = 0;//判断是否重新开始

public static void main(String[] args){

EventQueue.invokeLater(new Runnable()

{

public void run()

{

DrawFrame frame = new DrawFrame();

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

frame.setVisible(true);

}

});

}

}

class DrawFrame extends JFrame{

public DrawFrame()

{

setTitle("DisplayClock");//设置显示窗的标题

setSize(DEFAULT_WIDTH,DEFAULT_HEIGHT);//设置窗口的大小

DrawComponent component = new DrawComponent();

//创建要建立的图形的对象

add(component);

//将该图形加入到面板上

}

public static final int DEFAULT_WIDTH = 500;

//设置窗口的宽度

public static final int DEFAULT_HEIGHT = 500;

//设置窗口的高度

}

//建立时钟图形

class DrawComponent extends JComponent

{

public void paintComponent(Graphics g)

{

g.setColor(Color.blue);

Graphics2D g2 = (Graphics2D) g;

Ellipse2D circle = new Ellipse2D.Double();

circle.setFrameFromCenter(200,200,300,300);

g2.draw(circle);

//用来写表盘上的刻度

g.setColor(Color.green);

double jiaodu = Math.PI / 2;

double keX[] = new double[60];//存放表盘刻度的起始X坐标

double keY[] = new double[60];//存放表盘刻度的起始Y坐标

double duX[] = new double[60];//存放表盘刻度的终止X坐标

double duY[] = new double[60];//存放表盘刻度的终止Y坐标

for(int i = 0;i < 60;i++){

if(i == 0||i%5 == 0)

{

keX[i] = 200 + 80 * Math.cos(jiaodu);

keY[i] = 200 - 80 * Math.sin(jiaodu);

}

else

{

keX[i] = 200 + 90 * Math.cos(jiaodu);

keY[i] = 200 - 90 * Math.sin(jiaodu);

}

duX[i] = 200 + 100 * Math.cos(jiaodu);

duY[i] = 200 - 100 * Math.sin(jiaodu);

jiaodu = jiaodu - Math.PI / 30;

}

for(int j =0;j < 60;j++){

g2.draw(new Line2D.Double(keX[j],keY[j],duX[j],duY[j]));

}

//画12点的指针秒针

g.setColor(Color.black);

g2.draw(new Line2D.Double(200,200,200,130));

//画出分针

g.setColor(Color.BLUE);

g2.draw(new Line2D.Double(200,200,200,140));

//画出时针

g.setColor(Color.PINK);

g2.draw(new Line2D.Double(200,200,200,150));

}

}