Birthday.java

public class Birthday {
    public static void main(String[] args) {
        int n = Integer.parseInt(args[0]);
        int trials = Integer.parseInt(args[1]);
        int cumulative_sum = 0;
        int[] count = new int[n + 2];
        for (int i = 0; i < trials; i++) {
            boolean[] birthdays = new boolean[n];
            int c = 0;
            while (true) {
                int r = (int) (Math.random() * (n));
                c++;
                if (birthdays[r]) {
                    count[c]++;
                    break;
                }
                birthdays[r] = true;
            }
        }
        for (int i = 1; i < n + 2; i++) {
            cumulative_sum += count[i];
            double fraction = (double) cumulative_sum / trials;
            System.out.println(i + "\t" + count[i] + "\t" + fraction);
            if (fraction >= 0.5) break;
        }
    }
}