Original Life (as an application)

This is version 0. It is the version I wrote originally to run as an application.

Syntax of call	java Life size nsteps x1 y1 x2 y2 ... xn yn
Example call	java Life   8 10   3 4   4 5   5 3   5 4   5 5

Top     Version 1    

Source code:

/**
 * A Cell is one element of a two-dimensional array in John Conway's
 * "Game of Life."  It is either "alive" or "dead."
 * @author Dave Matuszek
 */

class Cell
{
  boolean alive = false;

  /**
   * Constructs a Cell in a given state (alive or dead).
   */
  Cell (boolean alive)
  {
    this.alive = alive;
  }

  /**
   * Constructs a Cell in a "dead" state.
   */
  Cell ()
  {
    this (false);
  }

  /**
   * Sets this cell to be alive or dead.
   */
  void setAlive (boolean alive)
  {
    this.alive = alive;
  }

  /**
   * Returns the state (alive or dead) of this cell.
   */
  boolean getAlive ()
  {
    return alive;
  }

  /**
   * Returns the state (alive or dead) of this cell, given its
   * coordinates in the array.
   */
  static boolean isAlive (int i, int j)
  {
    return Life.board[i][j].getAlive ();
  }

  /**
   * Count the number of living cells adjacent to this one.
   * Cells outside the array bounds are considered "dead."
   */
  static int countLiveNeighbors (int i, int j)
  {
    int limit = Life.width - 1;
    int count = 0;
    for (int ii = i - 1; ii <= i + 1; ii++)
      for (int jj = j - 1; jj <= j + 1; jj++)
      {
	if (ii == i && jj == j) continue;
	if (ii < 0 || ii > limit) continue;
	if (jj < 0 || jj > limit) continue;
	if (isAlive (ii, jj)) count++;
      }
    return count;
  }
}

/**
 * Life is the application class for John Conway's "Game of Life."
 * @author Dave Matuszek
 */
public class Life
{
  /** The size of the (square) playing board. */
  static int width;

  /** The playing board. */
  static Cell[][] board;

  /** A scratch area to use while computing the next board. */
  static Cell[][] nextBoard;

  /** Number of steps to run the game. */
  static int numberOfSteps;

  /**
   * A constructor to set up the playing board.  All cells are
   * initially set to "dead," then the cells indicated on the command
   * line are set to "alive".
   */
  Life (String args[])
  {
    width = Integer.parseInt (args[0]);
    board = new Cell[width][width];
    
    for (int i = 0; i < width; i++)
      for (int j = 0; j < width; j++)
        board[i][j] = new Cell ();

    int ii, jj;
    for (int i = 2; i < args.length; i += 2)
    {
      ii = Integer.parseInt (args[i]);
      jj = Integer.parseInt (args[i + 1]);
      board[ii][jj].setAlive (true);
    }
  }

  /**
   * Creates an empty (all cells dead) playing board of the given width.
   */
  static Cell[][] emptyBoard (int width)
  {
    Cell[][] result = new Cell[width][width];

    for (int i = 0; i < width; i++)
      for (int j = 0; j < width; j++)
        result[i][j] = new Cell ();
    return result;
  }

  /**
   * Prints out the current board.
   */
  static void print ()
  {
    for (int i = 0; i < width; i++)
    {
      for (int j = 0; j < width; j++)
        System.out.print ((Cell.isAlive (i, j) ? " *" : " ."));
      System.out.println ("");
    }
    System.out.println ("");
  }

  /**
   * Sets up and plays a game of Life.
   */

  public static void main (String args[])
  {
    Life life = new Life (args);
    print ();

    numberOfSteps = Integer.parseInt (args[1]);
    int numberOfNeighbors;

    for (int step = 0; step < numberOfSteps; step++)
    {
      // Set up an empty board and fill it with value for next step
      nextBoard = emptyBoard (width);
      for (int i = 0; i < width; i++)
        for (int j = 0; j < width; j++)
        {
          numberOfNeighbors = Cell.countLiveNeighbors (i, j);
          if (Cell.isAlive (i, j))
	  {
	    if (numberOfNeighbors == 2 || numberOfNeighbors == 3)
	      nextBoard[i][j].setAlive (true);
	  }
	  else // cell is dead
	    if (numberOfNeighbors == 3)
	      nextBoard[i][j].setAlive (true);
        }

      // Replace the current board with the new one
      board = nextBoard;
      print ();
    }
  }
}