//RecursionDemo.java

import java.util.Scanner;

public class RecursionDemo
{
    public static void main(String[] args)
    {
        System.out.println("Enter an integer:");
        Scanner keyboard = new Scanner(System.in);
        int number = keyboard.nextInt();
        System.out.println("The digits in that number are:");
        displayAsWords(number);
        System.out.println();

        System.out.println("If you add ten to that number, ");
        System.out.println("the digits in the new number are:");
        number = number + 10;
        displayAsWords(number);
        System.out.println();
    }

    /**
     * Precondition: number >= 0.
     * Displays the digits in number as words.
     */
    public static void displayAsWords
    (
        int number
    )
    {
        if (number < 10)
            System.out.print(getWordFromDigit(number) + " ");
        else //number has two or more digits
        {
            displayAsWords(number / 10);
            System.out.print(getWordFromDigit(number % 10) + " ");
        }
    }

    /**
     * Precondition: 0 <= digit <= 9.
     * Returns the word for the argument digit.
     */
    private static String getWordFromDigit
    (
        int digit
    )
    {
        String result = null;
        switch (digit)
        {
        case 0:
            result = "zero";
            break;
        case 1:
            result = "one";
            break;
        case 2:
            result = "two";
            break;
        case 3:
            result = "three";
            break;
        case 4:
            result = "four";
            break;
        case 5:
            result = "five";
            break;
        case 6:
            result = "six";
            break;
        case 7:
            result = "seven";
            break;
        case 8:
            result = "eight";
            break;
        case 9:
            result = "nine";
            break;
        default:
            System.out.println("Fatal Error.");
            System.exit(0);
            break;
        }
        return result;
    }
}