ConvertMoneyToEnglish

ConvertMoneyToEnglish.java

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.HashMap;
import java.util.Map;

import org.junit.jupiter.api.Test;

public class ConvertMoneyToEnglish {

    public static String convertMoneyToEnglish(int i) {
        Map<Integer, String> firstDigit = new HashMap<>();
        firstDigit.put(0, "zero ");
        firstDigit.put(1, "one ");
        firstDigit.put(2, "two ");
        firstDigit.put(3, "three ");
        firstDigit.put(4, "four ");
        firstDigit.put(5, "five ");
        firstDigit.put(6, "six ");
        firstDigit.put(7, "seven ");
        firstDigit.put(8, "eight ");
        firstDigit.put(9, "nine ");
        //
        Map<Integer, String> tensDigit = new HashMap<>();
        tensDigit.put(0, "");
        tensDigit.put(1, "ten ");
        tensDigit.put(2, "twenty ");
        tensDigit.put(3, "thirty ");
        tensDigit.put(4, "forty ");
        tensDigit.put(5, "fifty ");
        tensDigit.put(6, "sixty ");
        tensDigit.put(7, "seventy ");
        tensDigit.put(8, "eighty ");
        tensDigit.put(9, "ninety ");
        //
        Map<Integer, String> teens = new HashMap<>();
        teens.put(10, "ten ");
        teens.put(11, "eleven ");
        teens.put(12, "twelve ");
        teens.put(13, "thirteen ");
        teens.put(14, "fourteen");
        teens.put(15, "fifteen ");
        teens.put(16, "sixteen ");
        teens.put(17, "seventeen ");
        teens.put(18, "eighteen ");
        teens.put(19, "nineteen ");
        //

        int ones;
        int tens;
        int hundreds;

        if (i < 10) {
            return firstDigit.get(i) + (i == 1 ? "dollar" : "dollars");
        } else if (i < 19) {
            return teens.get(i) + "dollars";
        } else if (i < 99) {
            ones = i % 10;
            tens = i / 10;
            return tensDigit.get(tens) + firstDigit.get(ones) + "dollars";
        } else if (i > 100) {
            ones = i % 10;
            tens = (i / 10) % 10;
            hundreds = i / 100;
            return firstDigit.get(hundreds) + "hundred and " + tensDigit.get(tens) + firstDigit.get(ones) + "dollars";
        }

        return null;

    }


    @Test
    public void test789() {
        String string = convertMoneyToEnglish(789);
        assertEquals(string, "seven hundred and eighty nine dollars");
    }

    @Test
    public void test101() {
        String string = convertMoneyToEnglish(101);
        assertEquals(string, "one hundred and one dollars");
    }

    @Test
    public void test21() {
        String string = convertMoneyToEnglish(21);
        assertEquals(string, "twenty one dollars");
    }

    @Test
    public void test16() {
        String string = convertMoneyToEnglish(16);
        assertEquals(string, "sixteen dollars");
    }

    @Test
    public void test9() {
        String string = convertMoneyToEnglish(9);
        assertEquals(string, "nine dollars");
    }

    @Test
    public void test1() {
        String string = convertMoneyToEnglish(1);
        assertEquals(string, "one dollar");
    }

    @Test
    public void test0() {
        String string = convertMoneyToEnglish(0);
        assertEquals(string, "zero dollars");
    }

}