Version 5

This is a trivial change. I pulled out some comments, and added calls to the Canvas method getSize. This might not work for you. If you get a gray area where the Life board should be (instead of blue and white ovals), your browser probably doesn't understand getSize. You need a more modern browser, or you need to view this applet using appletviewer. To see why this is a cool thing to do, run the applet using appletviewer, and change the size of the applet window. Everything is automatically resized to fit.

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Source code:

import java.awt.*;
import java.applet.Applet;

public class Life extends Applet
{
  int boardSize = 10;
  boolean[][] board = new boolean[boardSize][boardSize];
  Button stepButton;
  MyCanvas canvas;

  public void init ()
  {
    setLayout (new BorderLayout ());

    stepButton = new Button ("Step");
    add (BorderLayout.NORTH, stepButton);

    canvas = new MyCanvas (board, boardSize);
    add (BorderLayout.CENTER, canvas);

    for (int i = 0; i < boardSize; i++)
      for (int j = 0; j < boardSize; j++)
        board[i][j] = (i + j) % 3 == 0; // diagonal pattern
  }
}

class MyCanvas extends Canvas
{
  int boardSize;
  boolean board[][];

  MyCanvas (boolean[][] board, int boardSize)
  {
    this.board = board;
    this.boardSize = boardSize;
  }

  public void paint (Graphics g)
  {
    // Get the size, not of the applet, but of the canvas itself.
    // Among other reasons, this looks nicer if the window is resized.
    Dimension d = getSize ();
    int cellWidth = d.width / boardSize;
    int cellHeight = d.height / boardSize;

    for (int i = 0; i < boardSize; i++) {
      for (int j = 0; j < boardSize; j++) {
        if (board[i][j])
	  g.setColor (Color.blue);
	else
	  g.setColor (Color.white);
	g.fillOval (i * cellWidth, j * cellHeight, cellWidth, cellHeight);
      }
    }
  }
}