Integer_to_English_words_273.java

public class Integer_to_English_words_273 {
        private static final String[] belowTwenty = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine",
                "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "Eighteen", "Nineteen"};
        private static final String[] tens = {"", "", "Twenty", "Thirty", "Forty", "Fifty", "Sixty", "Seventy", "Eighty", "Ninety"};

        public static String numberToWords(int num) {
            if (num == 0) {
                return "Zero";
            }
            return helper(num);
        }

        private static String helper(int num) {
            StringBuilder result = new StringBuilder();
            if (num < 20) {
                result.append(belowTwenty[num]);
            } else if (num < 100) {
                result.append(tens[num / 10]).append(" ").append(belowTwenty[num % 10]);
            } else if (num < 1000) {
                result.append(helper(num / 100)).append(" Hundred ").append(helper(num % 100));
            } else if (num < 1000000) {
                result.append(helper(num / 1000)).append(" Thousand ").append(helper(num % 1000));
            } else if (num < 1000000000) {
                result.append(helper(num / 1000000)).append(" Million ").append(helper(num % 1000000));
            } else {
                result.append(helper(num / 1000000000)).append(" Billion ").append(helper(num % 1000000000));
            }
            return result.toString().trim();
        }

    public static void main(String[] args) {
        int num=1000000;
        String ans=numberToWords(num);
        System.out.println(ans);
    }
}