Algorithm Implementation/Simulation/Conway's Game of Life

Conway's Game of Life is a cellular automaton with two states for each cell. The following implementation(s) calculate the next generation.

Java

import java.io.*;
public class GOL{

	public static String boardToString (boolean[][] board, int xsize, int ysize){
		StringBuffer sb= new StringBuffer();  // used to print out the board at the end
		for (int i=0;i<xsize;i++){
			for (int j=0;j<ysize;j++){
				if (board [i][j]){
					sb.append('*');
				}else{
					sb.append(' ');
				}
			}
		sb.append("\n");	
		}
		return sb.toString();
	}
	
	public static boolean[][] strToBoolMatrix (String str, int xsize, int ysize){
		boolean [][] board = new boolean[xsize][ysize];  // converts an input string into the
		for (int i=0;i<xsize; i++){                      // boolean[][] used internally
			for (int j=0; j<ysize; j++){
				board[i][j] = str.charAt((i*xsize)+j) != '0';
			}
		}
		return board;
	}

	public static int mod (int x, int m){ // deals with java's % returning negative vals for 
		m = Math.abs(m);                   // negative inputs
		return (x % m + m) % m;
	}

	public static int getNeighborCount(boolean[][] board, int x, int y, int xsize, int ysize){
		int nc = 0;   // this function rather messily counts up the neighbors
		
		if (board[mod(x+1,xsize)][y]){
			nc++;
		}
		if (board[mod(x+1,xsize)][mod(y+1, ysize)]){
			nc++;
		}
		if (board[x][mod(y+1,ysize)]){
			nc++;
		}
		if (board[x][mod(y-1,ysize)]){
			nc++;
		}
		if (board[mod(x+1,xsize)][mod(y-1,ysize)]){
			nc++;
		}
		if (board[mod(x-1,xsize)][y]){
			nc ++;
		}
		if (board[mod(x-1,xsize)][mod(y-1,ysize)]){
			nc ++;
		}
		if (board[mod(x-1,xsize)][mod(y+1,ysize)]){
			nc ++;
		}
		return nc;
	}

	public static boolean getDot(boolean[][] board, int x, int y, int xsize, int ysize){
		// this function applies the rules of the game on one square
			
		return board[x][y] && getNeighborCount(board, x,y,xsize,ysize) == 2
			|| getNeighborCount(board,x,y,xsize,ysize) == 3;
	}

	
	public static void main(String[] args) throws java.io.FileNotFoundException, java.io.IOException{
		int xsize = Integer.parseInt(args[0]);  // takes board size off command line
		int ysize = Integer.parseInt(args[1]);
		int gen = Integer.parseInt(args[2]);    // number of generations
		FileReader fr = new FileReader(args[3]); // will read in board from a file
		BufferedReader br= new BufferedReader(fr);
		StringBuffer sb = new StringBuffer();
		String line = new String(br.readLine());
		while(line != null){ // reading file
			sb.append(line);
			line = br.readLine();
		}
		String s = sb.toString();
		boolean[][] board = strToBoolMatrix(s,xsize,ysize); // this is the game board
		for (int i=0; i<gen; i++){  // loops through the generations
			boolean[][] next = new boolean[xsize][ysize];  // empty board
			for (int j=0;j<xsize;j++){     // loops through x-axis for computing the next generation
				for (int k=0; k< ysize; k++){ // loops through y-axis
					next[j][k] = getDot(board,j,k,xsize,ysize); 
				}
			}
			board = next;    // use the 'next' array as the new 'board' array
		}
		System.out.println(boardToString(board,xsize,ysize)); // prints the board
	}
}