Java编写桌面时钟Applet源码解析

import java.util.*;
import java.awt.*;
import java.applet.*;
import java.text.*;

/**
 * Time!
 *
 * @author Rachel Gollub
 * @modified Daniel Peek replaced circle drawing calculation, few more changes
 */
public class Clock extends Applet implements Runnable {
    private volatile Thread timer;       // The thread that displays clock
    private int lastxs, lastys, lastxm,
                lastym, lastxh, lastyh;  // Dimensions used to draw hands 
    private SimpleDateFormat formatter;  // Formats the date displayed
    private String lastdate;             // String to hold date displayed
    private Font clockFaceFont;          // Font for number display on clock
    private Date currentDate;            // Used to get date to display
    private Color handColor;             // Color of main hands and dial
    private Color numberColor;           // Color of second hand and numbers
    private int xcenter = 80, ycenter = 55; // Center position

    public void init() {
        int x,y;
        lastxs = lastys = lastxm = lastym = lastxh = lastyh = 0;
        formatter = new SimpleDateFormat ("EEE MMM dd hh:mm:ss yyyy", 
                                          Locale.getDefault());
        currentDate = new Date();
        lastdate = formatter.format(currentDate);

        clockFaceFont = new Font("Serif", Font.PLAIN, 14);
        handColor = Color.blue;
        numberColor = Color.darkGray;

        try {
            setBackground(new Color(Integer.parseInt(getParameter("bgcolor"),
                                                     16)));
        } catch (NullPointerException e) {
        } catch (NumberFormatException e) {
        }
        try {
            handColor = new Color(Integer.parseInt(getParameter("fgcolor1"),
                                                   16));
        } catch (NullPointerException e) {
        } catch (NumberFormatException e) {
        }
        try {
            numberColor = new Color(Integer.parseInt(getParameter("fgcolor2"),
                                                     16));
        } catch (NullPointerException e) {
        } catch (NumberFormatException e) {
        }
        resize(300,300);              // Set clock window size
    }

    // Paint is the main part of the program
    public void update(Graphics g) {
        int xh, yh, xm, ym, xs, ys;
        int s = 0, m = 10, h = 10;
        String today;