Random Walkers java in a pgm

RandomWalkers.java

public class RandomWalkers

{

              public static void main(String[] args)

    {

        int N = Integer.parseInt(args[0]);

        int[] x = new int[N];        

        int[] y = new int[N];        

        int cellsToVisit = N*N;      

        int steps = 0;               

        double r;

        boolean[][] visited = new boolean[N][N]; 

        for (int i = 0; i < N; i++)

       {

            x[i] = N/2;

            y[i] = N/2;

        }

        visited[N/2][N/2] = true;

        cellsToVisit--;

                    while (cellsToVisit > 0)

        {

            steps++;

           

            for (int i = 0; i < N; i++)

            {

                r = Math.random();

                if      (r <= 0.25) {  x[i]++;  }

                else if (r <= 0.50) {  x[i]--;  }

                else if (r <= 0.75) {  y[i]++;  }

                else if (r <= 1.00) {  y[i]--;  }

                if (x[i] < N && y[i] < N && x[i] >= 0 && y[i] >= 0 && !visited[x[i]][y[i]])

               {

                    cellsToVisit--;

                    visited[x[i]][y[i]] = true;

                }

            }

        }

        System.out.println(steps);

    }

}