The Math program for applets

Here is the program in it's entirety:

• package com.blazinggames.jgd.chapter04;
• import java.applet.*;
• import java.awt.*;
• /**
• * Billy Spelchan's guide to Java Game Development
• * Chapter 4 sample applet
• * Copyright (c) 2003 Spelchan Software.
• * This source code is meant for educational purposes.
• * You may transfer and use this program for non-comercial purposes as long as
• * no fees are charged for this program.
• * The goal of this program is to demonstrate the structure of a Java applet.
• *
• * @author Billy D. Spelchan
• * @version 1.00.021118
• */
• public class Chapter04
• extends Applet
• {
  • // *********************
  • // ***** VARIABLES *****
  • // *********************
  • private int columnStart;
  • private int rowStart;

• • // ************************************
  • // ***** METHODS - Parameter Aids *****
  • // ************************************
  • /**
  • * Converts a string to a number, handling invalid numbers.
  • *
  • * @param s string to convert
  • * @param n number to return if string is invalid
  • */
  • private int stringToInt(String s, int n)
  • {
    • int result = n;
    • try
    • {
      • result = Integer.parseInt(s);
    • }
    • catch (NumberFormatException nfe)
    • {
      • result = n;
    • }
    • return result;
  • }
  • // *********************************
  • // ***** METHODS - From Applet *****
  • // *********************************
  • /**
  • * From Applet. Allows applet to initialize itself.
  • * This is the applet equivelent of a main() method.
  • */
  • public void init()
  • {
    • // print copyright info to console
    • System.out.println("Billy Spelchan's guide to Java Game Development");
    • System.out.println("Chapter 4 sample applet");
    • System.out.println("Copyright " + ((char)169) + " 2003 Spelchan Software.");
    • // get parameters
    • columnStart = stringToInt( getParameter("COLUMN_START"), 1);
    • rowStart = stringToInt( getParameter("ROW_START"), 1);
  • }
  • /**
  • * This gets called whenever the browser starts an applet.
  • */
  • public void start()
  • {
    • System.out.println("start()");
  • }
  • /**
  • * This gets called whenever the browser stops an applet.
  • */
  • public void stop()
  • {
    • System.out.println("stop()");
  • }
  • /**
  • * This gets called whenever the browser is going to destroy an applet.
  • */
  • public void destroy()
  • {
    • System.out.println("destroy()");
  • }
  • /**
  • * Draws the applet, in this case a multiplication table.
  • *
  • * @param g the graphics context to draw in
  • */
  • public void paint(Graphics g)
  • {
    • int cntrX, cntrY;
    • int math;
    • String s;
    • // draw grid
    • g.setColor(Color.blue);
    • for (cntrX = 0; cntrX < 12; ++cntrX)
    • {
      • g.drawLine(cntrX*50+45, 20, cntrX*50+45, 460);
      • g.drawLine(45, cntrX*40+20, 595, cntrX*40+20);
    • }
    • // fill in multipication table
    • FontMetrics fm = g.getFontMetrics();
    • for (cntrX = 1; cntrX < 11; ++cntrX)
    • {
      • for (cntrY = 1; cntrY < 11; ++cntrY)
      • {
        • math = ((cntrX - 1) + columnStart) * ((cntrY - 1) + rowStart);
        • s = "" + math;
        • g.drawString(s, cntrX*50+95-fm.stringWidth(s), cntrY*40+50);
      • }
    • }
    • // draw captions, in different color
    • g.setColor(Color.red);
    • for (cntrX = 1; cntrX < 11; ++cntrX)
    • {
      • math = ((cntrX - 1) + columnStart);
      • s = "" + math;
      • g.drawString(s, cntrX*50+95-fm.stringWidth(s), 50);
    • }
    • // these two loops could be combined, but separated for readablity
    • for (cntrY = 1; cntrY < 11; ++cntrY)
    • {
      • math = ((cntrY - 1) + rowStart);
      • s = "" + math;
      • g.drawString(s, 95-fm.stringWidth(s), cntrY*40+50);
    • }
  • }
• }