import static java.util.Calendar.HOUR;
import static java.util.Calendar.MILLISECOND;
import static java.util.Calendar.MINUTE;
import static java.util.Calendar.SECOND;
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.util.Calendar;
import javax.swing.ImageIcon;
import javax.swing.JPanel;
 
/**
 * 时钟面板
 * 
 * @author 听说你很会玩
 */
@SuppressWarnings("serial")
public class ClockPanel extends JPanel {
 // 3个指针的粗细
 private static final BasicStroke HOURS_POINT_WIDTH = new BasicStroke(4);
 private static final BasicStroke MINUETES_POINT_WIDTH = new BasicStroke(3);
 private static final BasicStroke SEC_POINT_WIDTH = new BasicStroke(2);
 ImageIcon background;// 背景图片对象
 private int centerX;// 中心坐标
 private int centerY;// 中心坐标
 private final static int secLen = 60; // 指针长度
 private final static int minuesLen = 55; // 指针长度
 private final static int hoursLen = 36; // 指针长度
  
 /**
 * 构造方法
 */
 public ClockPanel() {
 setToolTipText("小键盘+、-调整透明度，Crtl+Shift+X退出");// 提示信息
 setOpaque(false);
  
 background = new ImageIcon(getClass().getResource("clock.jpg"));// 加载图片
 int iconWidth = background.getIconWidth();// 获取图片大小
 centerX = iconWidth / 2;// 获取图片中间坐标
 int iconHeight = background.getIconHeight();
 centerY = iconHeight / 2;// 获取图片中间坐标
 setPreferredSize(new Dimension(iconWidth, iconHeight));
 }
  
 @Override
 public void paint(Graphics g) {// 重写父类方法
 Graphics2D g2 = (Graphics2D) g;
 g2.drawImage(background.getImage(), 0, 0, this);// 绘制背景图片
 Calendar calendar = Calendar.getInstance();// 获取日历对象
 int millisecond = calendar.get(MILLISECOND);// 获取毫秒值
 int sec = calendar.get(SECOND);// 获取秒值
 int minutes = calendar.get(MINUTE);// 获取分值
 int hours = calendar.get(HOUR);// 获取时值
 double secAngle = (60 - sec) * 6 - (millisecond / 150); // 秒针角度
 int minutesAngle = (60 - minutes) * 6;// 分针角度
 int hoursAngle = (12 - hours) * 360 / 12 - (minutes / 2);// 时针角度
 // 计算秒针、分针、时针指向的坐标
 int secX = (int) (secLen * Math.sin(Math.toRadians(secAngle)));// 秒针指向点的X坐标
 int secY = (int) (secLen * Math.cos(Math.toRadians(secAngle))); // 秒针指向点的Y坐标
 int minutesX = (int) (minuesLen * Math
 .sin(Math.toRadians(minutesAngle))); // 分针指向点的X坐标
 int minutesY = (int) (minuesLen * Math
 .cos(Math.toRadians(minutesAngle))); // 分针指向点的Y坐标
 int hoursX = (int) (hoursLen * Math.sin(Math.toRadians(hoursAngle))); // 时针指向点的X坐标
 int hoursY = (int) (hoursLen * Math.cos(Math.toRadians(hoursAngle))); // 时针指向点的Y坐标
 // 分别绘制时针、分针、秒针
 g2.setStroke(HOURS_POINT_WIDTH);// 设置时针的宽度
 g2.setColor(Color.BLACK);// 设置时针的颜色
 g2.drawLine(centerX, centerY, centerX - hoursX, centerY - hoursY);// 绘制时针
 g2.setStroke(MINUETES_POINT_WIDTH);// 设置分针的宽度
 if (minutesAngle != hoursAngle) // 分针、时针重叠变色
 g2.setColor(new Color(0x2F2F2F));// 设置未重叠时的颜色
 else {
 g2.setColor(Color.GREEN);// 设置重叠时的颜色
 }
 g2.drawLine(centerX, centerY, centerX - minutesX, centerY - minutesY);// 绘制分针
 g2.setStroke(SEC_POINT_WIDTH);// 设置秒针的宽度
 if (secAngle != hoursAngle && secAngle != minutesAngle)// 分针、时针、秒针重叠变色
 g2.setColor(Color.ORANGE);// 设置未重叠时的颜色
 else {
 g2.setColor(Color.GREEN);// 设置重叠时的颜色
 }
 // 绘制3个指针的中心圆和秒针
 g2.fillOval(centerX - 5, centerY - 5, 10, 10);// 绘制中心圆
 g2.drawLine(centerX, centerY, centerX - secX, centerY - secY);// 绘制秒针
 g2.drawLine(centerX + 1, centerY + 1, centerX - secX + 1, centerY
 - secY + 1);// 绘制秒针
 }
}

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
 
/**
 * @author 张振坤
 */
@SuppressWarnings("serial")
public class ClockFrame extends JDialog {
 private float opqua = 0.7f;
 private ClockPanel clockPanel;
 private Point fp; // 拖曳窗体之前的鼠标位置
  
 public static void main(String args[]) {
 EventQueue.invokeLater(new Runnable() {
  public void run() {
  try {
   ClockFrame frame = new ClockFrame();// 创建窗体对象
   frame.setVisible(true);// 显示窗体
  } catch (Exception e) {
   e.printStackTrace();
  }
  }
 });
 }
  
 /**
 * 布局窗体的构造方法
 */
 public ClockFrame() {
 super();
 setUndecorated(true);// 取消窗体修饰
 setAlwaysOnTop(true);// 窗体置顶
 setTitle("石英钟");// 设置窗体标题
 getContentPane().setLayout(new BorderLayout());
 setBounds(100, 30, 217, 257);
 setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);
 clockPanel = new ClockPanel();// 创建时钟面板
 getContentPane().add(clockPanel);
 // 为时钟面板添加鼠标按键事件监听器
 clockPanel.addMouseListener(new MouseAdapter() {
  public void mousePressed(final MouseEvent e) {
  fp = e.getPoint();
  if (e.getButton()==MouseEvent.BUTTON3){
   System.exit(0);// 右键退出
  }
  }
 });
 // 在时钟面板的鼠标拖曳事件中移动窗体
 clockPanel.addMouseMotionListener(new MouseMotionAdapter() {
  public void mouseDragged(final MouseEvent e) {
  JDialog frame = (JDialog) getRootPane().getParent();
  Point point = e.getLocationOnScreen();
  frame.setLocation(point.x - fp.x, point.y - fp.y);
  }
 });
 pack();
  
 addKeyListener(new KeyAdapter() {// 为窗体添加键盘事件监听器
  public void keyPressed(final KeyEvent e) {
  int code = e.getKeyCode();
  switch (code) {// 判断按键编码
   case KeyEvent.VK_ADD:// +符号按键会降低透明图
   opqua += 0.05;
   opqua = opqua > 0.95f ? 1f : opqua;
   break;
   case KeyEvent.VK_SUBTRACT:// -符号按键会提升透明度
   opqua -= 0.05;
   opqua = opqua < 0.1f ? 0.1f : opqua;
   break;
  }
  // 如果按Ctrl+Shift+X組合鍵，将退出程序
  if (code == KeyEvent.VK_X
   && e.getModifiersEx() == (KeyEvent.CTRL_DOWN_MASK | KeyEvent.SHIFT_DOWN_MASK))
   System.exit(0);
  }
 });
  
 Dimension screenSize = getToolkit().getScreenSize();
 double width = screenSize.getWidth();
 int x = (int) (width - getWidth() - 30);
 setLocation(x, 30);
  
 new Thread() {// 创建线程对象，更新时钟面板界面
  @Override
  public void run() {
  try {
   while (true) {
   sleep(1000);// 休眠1秒
   clockPanel.repaint();// 重新绘制时钟面板界面
   }
  } catch (InterruptedException e) {
   e.printStackTrace();
  }
  }
 }.start();
 }
}