Convert a non-negative integer num to its English words representation. Example 1: Input: num = 123 Output: "One Hundred Twenty Three" Example 2: Input: num = 12345 Output: "Twelve Thousand Three Hundred Forty Five" Example 3: Input: num = 1234567 Output: "One Million Two Hundred Thirty Four Thousand Five Hundred Sixty Seven"

import java.util.*;

public class Main {
  public static void main(String[] args) {
    System.out.println("Hello world!");
    
    System.out.println(numberToWords(123));
  }//end main
  
  public static String numberToWords(int num) {
  if (num == 0)
      return "Zero";
  
  int i = 0;
  String words = "";

  while (num > 0) {
    if (num % 1000 != 0)
      words = helper(num % 1000) + THOUSANDS[i] + " " + words;
    num /= 1000;
    i++;
  }
  
  return words.trim();
}

  private final static String[] LESS_THAN_20 = {"", "One", "Two", "Three", "Four", "Five", "Six", "Seven", "Eight", "Nine", "Ten", "Eleven", "Twelve", "Thirteen", "Fourteen", "Fifteen", "Sixteen", "Seventeen", "