Question

JAVA. Threading the Game of Life

Write a Java program to implement the Game of Life, as defined by John Conway:

Any live cell with fewer than two live neighbors dies, as if caused by under-population.

Any live cell with two or three live neighbors lives on to the next generation.

Any live cell with more than three live neighbors dies, as if by overpopulation.

Any dead cell with exactly three live neighbors becomes a live cell, as if by reproduction.

Your program should use a 20 x 20 grid, and accept the initial grid configuration from a text file named "startinggrid.txt", in a form similar to the following (this example would be for a 4 x 4 grid):

OOOO

OXXO

OXXO

OOOO

Where ‘X’ indicates and inhabited square and ‘O’ indicates an empty square. The last line of the text file (the 21st line) will contain a single integer, indicating the number of generations to compute, and show the final configuration in the same format as the input.

****THIS IS AN EXERCISE IN THREADING. USE A SEPARATE THREAD FOR EACH SQUARE IN YOUR GRID!****

Answer 1

Code:

import java.io.File;
import java.util.Scanner;

/**
*
* @author pc
*/
//Implement Runnable in this class MyThread to overwrite the run method from Runnable
class MyThread implements Runnable
{
private char grid[][],inter[][];
int x, y;
//initialize all the variables in the constructor like square index , grid,inter
public MyThread(int x,int y,char [][]grid,char [][]inter)
{
this.x=x;
this.y=y;
this.grid=grid;
this.inter=inter;
}
//find the status for x,y square for next generation
public boolean makeAlive()
{
int neigh=0;
for(int i=x-1;i<=x+1;i++)
{
for(int j=y-1;j<=y+1;j++)
{
if((i!=x || j!=y) && i>=0 && j>=0 && i<20 && j<20 && grid[i][j]=='X')
{
neigh++;
}
}
}
//if this sqare is dead and it has exact three neighbur then make it alive
if(grid[x][y]=='O' && neigh==3)
return true;
if(grid[x][y]=='X' && (neigh==2||neigh==3))//if it is alive and it has either 2 or 4 neighbours then keep it alive for next generation
return true;
return false;//otherwise make it dead
}
//every thread on calling start() willl call run() method and will update value in intermediate grid(inter) by extracting input from grid[][]
@Override
public void run() {
boolean alive=makeAlive();
if(alive)//if it is supposed to be alive for next generation then mak it alive in next generation
inter[x][y]='X';
else
inter[x][y]='O';
}
}

class GameofLife
{
//to store grid
private char grid[][]=new char[20][20];
//to store intermediate values for next generation
private char inter[][]=new char[20][20];
//read file into grid and generation value
public int readFile()
{
int index=0,gen=1;
try{
File file=new File("E:\\startinggrid.txt");
Scanner sc=new Scanner(file);
while(sc.hasNext())
{
String str=sc.next();
//if length is 20 then read it in array
if(str.length()==20)
{
for(int j=0;j<20;j++)
{
grid[index][j]=str.charAt(j);
  
}
index++;
}
else{
gen=Integer.parseInt(str);
break;
}
}
sc.close();
}catch(Exception e)
{
System.out.println(e);
}
return gen;//return gen
}
//copy inter into grid at end of each generation
public void copyInterIntoGrid()
{
for(int i=0;i<20;i++)
{
for(int j=0;j<20;j++)
{
grid[i][j]=inter[i][j];
}
}
}
//process data for generation one at a time
public void process()
{
//create 20*20 thread for each square
Thread t[]=new Thread[400];
int index=0;//index
//instantiate thread
for(int i=0;i<20;i++)
{
for(int j=0;j<20;j++){
t[index] = new Thread(new MyThread(i,j,grid,inter));
t[index].start();//start
index++;
}
}
try{
//keep this main thread on hold untill all the other threads finish their work
for(int i=0;i<400;i++)
t[i].join();
}catch(Exception e)
{
System.out.println(e);
}
copyInterIntoGrid();//copy inter into grid
}
public static void main(String[] args) {
GameofLife gof=new GameofLife();
int gen=gof.readFile();
//process for each generation
for(int i=0;i<gen;i++)
{
gof.process();
}
//printing process
System.out.println("Final output after at last generation");
for(int i=0;i<20;i++)
{
for(int j=0;j<20;j++)
{
System.out.print(String.valueOf(gof.grid[i][j]));
}
System.out.println("");
}
}
  
  
}

Input File (startinggrid.txt):

OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOXXXXOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOXXXOOXXOOXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXOOXXOXXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OXXOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
XOXOOOOOOXXXXXOOOXXO
OOOOOXXXOXXXXXOOOXXO
OOOOOOOOOXXXXXOOOXXO
XXXXXXXXXXXXXXOOOXXO
1