Four (updated)

import java.util.Scanner;

public class Numbers {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int theNum = 0;

        do{
            System.out.println("Input a number between 0 and " + (words.length-1));
            theNum = sc.nextInt();
        }while(theNum<0 || theNum>(words.length-1));

        while(theNum != 4){
            int temp = numToStr(theNum).length();
            System.out.println(numToStr(theNum) + " is " + numToStr(temp));
            theNum = temp;
        };

        System.out.println("Four is the magic number.");

    }

    private final static String[] words = {
        "Zero",
        "One",
        "Two",
        "Three",
        "Four",
        "Five",
        "Six",
        "Seven",
        "Eight",
        "Nine",
        "Ten",
        "Eleven",
        "Twelve",
        "Thirteen",
        "Fourteen",
        "Fifteen",
        "Sixteen",
        "Seventeen",
        "Eighteen",
        "Nineteen",
        "Twenty",
        "Twentyone",
        "Twentytwo",
        "Twentythree",
        "Twentyfour",
        "Twentyfive",
        "Twentysix",
        "Twentyseven",
        "Twentyeight",
        "Twentynine",
        "Thirty",
        "Thirtyone",
        "Thirtytwo",
        "Thirtythree",
        "Thirtyfour",
        "Thirtyfive",
        "Thirtysix",
        "Thirtyseven",
        "Thirtyeight",
        "Thirtynine",
        "Forty",
        "Fortyone",
        "Fortytwo",
        "Fortythree",
        "Fortyfour",
        "Fortyfive",
        "Fortysix",
        "Fortyseven",
        "Fortyeight",
        "Fortynine",
        "Fifty"
    };

    public static String numToStr(int num){
        if(num<0 || num>words.length){
            throw new RuntimeException("Invalid number");
        }
        return words[num];
    }

}