RollSimulation.java

import java.util.Random;

public class RollSimulation {
    public static void main(String[] args) {
        Random rand = new Random();

        for (int f = 1; f <= 6; f++) {
            int[] rolls1 = new int[8];
            int[] rolls2 = new int[8];

            // use both methods to generate rolls, one million iterations each
            for (int i = 0; i < 1e5; i++) {
                rolls1[nextRoll1(f, rand)]++;
                rolls2[nextRoll2(f, rand)]++;
            }

            // print out method 1
            System.out.print("r1 f=" + f + ", ");
            for (int i = 1; i <= 6; i++) {
                double prob = rolls1[i]/1e5*100;
                System.out.printf("%d: %s%.2f%%", i, prob == 0 ? " " : "", prob);
                System.out.print(i == 6 ? "\n" : "   ");
            }

            // print out method 2
            System.out.print("r2 f=" + f + ", ");
            for (int i = 1; i <= 6; i++) {
                double prob = rolls2[i]/1e5*100;
                System.out.printf("%d: %s%.2f%%", i, prob == 0 ? " " : "", prob);
                System.out.print(i == 6 ? "\n" : "   ");
            }

            System.out.print("\n");
        }
    }

    public static int nextRoll1(int forbidden, Random rand) {
        int r = rand.nextInt (5) + 1;

        if (r >= forbidden)
            r = r + 1;

        return r;
    }

    public static int nextRoll2 (int forbidden, Random rand) {
        int r = rand.nextInt (6) + 1;

        while (r == forbidden)
            r = rand.nextInt (6) + 1;

        return r;
    }
}