NinetyNineProblem.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;

/**
 * Created by Gergo on 2014.09.19..
 */
public class NinetyNineProblem {

    static Integer[] riddleArray = new Integer[99];
    static Random random = new Random();

    static void initRiddle(){
        int rand = random.nextInt(101);
        final int missingNum;
        if (rand == 0) {
            missingNum = rand + 1;
        } else {
            missingNum = rand;
        }
        System.out.println(missingNum);
        for (int i = 1; i < missingNum; i++) {
            riddleArray[i-1] = i;
        }

        for (int j = missingNum; j < 100; j++) {
            riddleArray[j-1] = j+1;
        }
    }

    static int findMissingNumber(Integer... array) {
        ArrayList<Integer> va = new ArrayList<>();
        Collections.addAll(va, riddleArray);
        int counter = 1;
        Boolean notFound = true;
        while (notFound) {
            if (va.contains(counter)){
                counter++;
            } else {
                notFound = false;
                return counter;
            }
        }
        return 0;
    }

    public static void main(String[] args) {
        initRiddle();
        System.out.println(findMissingNumber(riddleArray));
    }
}