LACS00_RandomWalk.java

/**
RandomWalk.java     MrG 2012.0525
purpose:    test StdDraw class and simulate random walk!
required files: RandomWalk.java             main class
        StdDraw.java                graphics class
translator: javac RandomWalk.java
interpreter:    java RandomWalk N
*/
public class RandomWalk
{
    public static void main(String[] args)
    {
        int N = Integer.parseInt(args[0]);
        StdDraw.setXscale(-N,N);
        StdDraw.setYscale(-N,N);
        StdDraw.clear(StdDraw.GRAY);

        int x=0;
        int y=0;
        int steps = 0;
        while(Math.abs(x)<N && Math.abs(y)<N)
        {
            StdDraw.setPenColor(StdDraw.WHITE);
            StdDraw.filledSquare(x,y,0.45);
            double r = Math.random();
            if  (r<0.25){x--;}
            else if (r<0.50){x++;}
            else if (r<0.75){y--;}
            else if (r<1.00){y++;}
            steps++;
            StdDraw.setPenColor(StdDraw.BLUE);
            StdDraw.filledSquare(x,y,0.45);
            StdDraw.show(40);
        }
        System.out.println("total steps = " + steps);
    }
}