16b. Numbers 0..100 to Text

/**
 * Project: Simple_Conditions - created by borkins on 2017-03-25.
 */

import java.util.Scanner;

public class _16b_Numbers_0_100_toText
{
    public static void main(String[] args)
    {
        Scanner scan = new Scanner(System.in);

        int number = Integer.parseInt(scan.nextLine());

        String units = "";
        String tenths = "";

        switch (number % 10)
        {
            case 0: units = "zero"; break;
            case 1: units = "one"; break;
            case 2: units = "two"; break;
            case 3: units = "three"; break;
            case 4: units = "four"; break;
            case 5: units = "five"; break;
            case 6: units = "six"; break;
            case 7: units = "seven"; break;
            case 8: units = "eight"; break;
            case 9: units = "nine"; break;
        }

        switch ((number / 10))
        {
            case 1:
                switch (number % 10)
                {
                    case 0: tenths = "ten"; break;
                    case 1: tenths = "eleven"; break;
                    case 2: tenths = "twelve"; break;
                    case 3: tenths = "thirteen"; break;
                    case 4: tenths = "fourteen"; break;
                    case 5: tenths = "fifteen"; break;
                    case 6: tenths = "sixteen"; break;
                    case 7: tenths = "seventeen"; break;
                    case 8: tenths = "eighteen"; break;
                    case 9: tenths = "nineteen"; break;
                }
                break;

            case 2: tenths = "twenty"; break;
            case 3: tenths = "thirty"; break;
            case 4: tenths = "forty"; break;
            case 5: tenths = "fifty"; break;
            case 6: tenths = "sixty"; break;
            case 7: tenths = "seventy"; break;
            case 8: tenths = "eighty"; break;
            case 9: tenths = "ninety"; break;
        }

        if (number < 0 || number > 100) {
            System.out.println("invalid number");
        }
        // In that point we are sure that the number is in the range 0..100.
        // If true, number is between 0 and 9, then print numbers: 'zero', 'one', 'two'...'nine'.
        else if (number < 10) {
            System.out.println(units);
        }
        // If number is between 10 and 19, print numbers: 'ten', 'eleven', 'twelve'...'nineteen'.
        // OR if number is between 20..99 AND the digit in the units is 0,
        // print numbers: 'twenty', 'thirty', 'forty'...'ninety'.
        else if (number < 20 || (number < 100 && number % 10 == 0)) {
            System.out.println(tenths);
        }
        // If number is between 20 and 99, print the numbers with two words.
        else if (number < 100) {
            System.out.println(tenths + " " + units);
        }
        // The number is 100, print 'one hundred'.
        else {
            System.out.println("one hundred");
        }
    }
}