Flip.java

/*************************************************************************
 *  Compilation:  javac Flip.java
 *  Execution:    java Flip N
 *  Dependencies: StdDraw.java
 *  
 *  Each experiment consists of flipping N fair coins. Plots (in real
 *  time) a histogram of the number of times i of the N coins are heads.
 *
 *  % java Flip 32
 *
 *  % java Flip 64
 *
 *  % java Flip 128
 *
 *************************************************************************/


public class Flip { 
    public static void main(String[] args) { 
        int N = Integer.parseInt(args[0]);   // number of coins to flip
        int[] freq = new int[N+1];           // freq[i] = # times you get i heads
        int freqMax = 500;                   // stop when one bucket has this many heads
 
        StdDraw.create(600, 400);
        StdDraw.setScale(0, 0, N, freqMax);

        while (true) {
            int heads = 0;

            // flip N coins and tabulate the results
            for (int j = 0; j < N; j++)
                if (Math.random() < 0.5) heads++;
            freq[heads]++;

            // plot next box in histogram
            StdDraw.go(heads, freq[heads]);
            StdDraw.spot(0.5, 1.0);
            StdDraw.pause(5);

            // stop when it goes outside window
            if (freq[heads] >= freqMax) break;
        }
        StdDraw.show();
    }
}