WillYouChangeYourChoice.java

import java.util.*;

/**
 * Created by master Alish on 4/19/17.
 */
public class WillYouChangeYourChoice {
    private static final int TRIES = 1000;
    private static final int VARS = 3;
    private static boolean[] choices = new boolean[VARS];
    private static int myChoice;
    private static int totallyWrongChoiceThatIsNotChosenByMe;
    private static Random rnd = new Random();

    public static void main(String[] args) {
        checkWhenIDoNotChangeMyChoice();
        checkWhenIChangeMyChoice();
    }

    private static void checkWhenIDoNotChangeMyChoice() {
        int iWinCounts = 0;
        for(int i=0; i<TRIES; i++) {
            choices = generateRandomVariants();
            myChoice = chooseRandomVariant();
            totallyWrongChoiceThatIsNotChosenByMe = getTotallyWrongChoiceThatIsNotChosenByMe(myChoice, choices);
            myChoice = myChoice;
            if (choices[myChoice]){
                iWinCounts ++;
            }
        }

        System.out.println(String.format("I win %d times of %d tries when I did not change my choice", iWinCounts, TRIES));
    }

    private static void checkWhenIChangeMyChoice() {
        int iWinCounts = 0;
        for(int i=0; i<TRIES; i++) {
            choices = generateRandomVariants();
            myChoice = chooseRandomVariant();
            totallyWrongChoiceThatIsNotChosenByMe = getTotallyWrongChoiceThatIsNotChosenByMe(myChoice, choices);
            myChoice = changeChoice(myChoice, totallyWrongChoiceThatIsNotChosenByMe);
            if (choices[myChoice]){
                iWinCounts ++;
            }
        }

        System.out.println(String.format("I win %d times of %d tries when I change my choice", iWinCounts, TRIES));
    }

    private static int changeChoice(int myChoice, int totallyWrongChoiceThatIsNotChosenByMe) {
        Set<Integer> allChoices = new HashSet<>();

        allChoices.add(0);
        allChoices.add(1);
        allChoices.add(2);

        allChoices.remove(myChoice); // not my choice
        allChoices.remove(totallyWrongChoiceThatIsNotChosenByMe); //not wrong choice

        return (int) allChoices.toArray()[0]; // last choice
    }

    private static boolean[] generateRandomVariants() {
        boolean[] vars = new boolean[VARS];
        vars[rnd.nextInt(VARS)] = true;
        return vars;
    }

    private static int chooseRandomVariant() {
        return rnd.nextInt(VARS);
    }

    private static int getTotallyWrongChoiceThatIsNotChosenByMe(int myChoice, boolean[] choices) {
        for(int i=0;i<choices.length; i++){
            if(choices[i] == false && myChoice != i){
                return i;
            }
        }
        throw new RuntimeException("Something went wrong");
    }
}