Prints the textual representation of integer in English.

NumberWords.java

/**
 * The program takes 2 parameters for the main method:
 * 	- first parameter is the number to be converted
 * 	- second parameter is either 1 or 2. 1 represents question 1 and 2 represents question 2
 * 
 * @author armaan
 *
 */
public class NumberWords {

	/**
	 * The output should be this file which, when run, will output your answers to the following problems.
	 * 
	 *    1. When passed a single integer between 0 and 10 the program should print out the textual representation
	 *       of that integer in English.  E.g. given the integer 4 your program should print 'four'.
	 *    
	 *    2. Extend your solution in Q1 to support all integers between 0 and 99999.  Consider all cases necessary; 
	 *       for example
	 *          - '10001' should print 'Ten Thousand and One'. 
	 *          - '6415'  should print 'Six Thousand Four Hundred and Fifteen'.
	 *          - '93467' should print 'Ninety Three Thousand Four Hundred and Sixty Seven'.
	 *          
	 * Program should compile and will be passed each of the integers below as the first entry in the args array passed to the main method.
	 * It should print out each one in the form '1234 : One Thousand Two Hundred and Thirty Four'.
	 *    
	 * Question 1 Test Numbers: 0, 2, 4, 6, 8, 10
	 * Question 2 Test Numbers: 0, 2, 11, 17, 23, 100, 114, 756, 1010, 5500, 10000, 10001, 14389, 99999
	 * 
	 */
	
	private static final String[] numberNames = {
		    "",
		    "one",
		    "two",
		    "three",
		    "four",
		    "five",
		    "six",
		    "seven",
		    "eight",
		    "nine",
		    "ten",
		    "eleven",
		    "twelve",
		    "thirteen",
		    "fourteen",
		    "fifteen",
		    "sixteen",
		    "seventeen",
		    "eighteen",
		    "nineteen"
		  };
	
	private static final String[] tenNames = {
		    "",
	        "ten",
	        "twenty",
	        "thirty",
	        "forty",
	        "fifty",
	        "sixty",
	        "seventy",
	        "eighty",
	        "ninety"	
	};
	
	
	/**
	 * This method handles the solution to Question 1.
	 * @param number	number to be converted to it's word representation.
	 * @return String	converted word string from a number
	 */
	public String convert1To10(int number) {
		if(number < 0 || number > 10) {
			return "Number entered is out of bounds";
		}
		else if(number == 0){
			return "Zero";
		}
		else {
			String input = numberNames[number];
			return input.substring(0, 1).toUpperCase() + input.substring(1);
		}
	}
	
	/**
	 * Private utility function that handles numbers upto 99
	 * @param number
	 * @return String	string representation of the number
	 */
	private String convertUpto99(int number){
		if(number <= 0 || number > 99) {
			return "Number entered is out of bounds";
		}
		else if(number < 20) {
			return numberNames[number];
		}
		else {
			return tenNames[number/10] + " " + numberNames[number%10];
		}
	}
	
	/**
	 * Private utility function that handles numbers upto 999
	 * @param number
	 * @return String	string representation of the number
	 */
	private String convertUpto999(int number) {
		StringBuilder word = new StringBuilder("");
		if(number <= 0 || number > 999) {
			return "Number entered is out of bounds";
		}
		else if(number < 100) {
			return convertUpto99(number);
		}
		else{
			word.append(numberNames[number/100]);
			number %= 100;
			if(number == 0){
				word.append(" hundred");
				return word.toString();
			}
			word.append(" hundred ");
			return word.append("and " + convertUpto99(number).toString()).toString();
		}
	}
	
	/**
	 * Private utility function that handles numbers upto 99999
	 * @param number
	 * @return String	string representation of the number
	 */
	private String convertUpto99999(int number){
		StringBuilder word = new StringBuilder("");
		if(number <= 0 || number > 99999) {
			return "Number entered is out of bounds";
		}
		else if(number < 1000) {
			return convertUpto999(number);
		}
		else{
			word.append(convertUpto99(number/1000));
			number %= 1000;
			if(number == 0){
				word.append(" thousand");
				return word.toString();
			}
			else if(number < 100 || number/100 < 9) {
				word.append(" thousand and ");
			}
			else{
				word.append(" thousand ");
			}
			return word.append(convertUpto999(number).toString()).toString();
		}
	}
	
	/**
	 * Represents the solution to question 2.
	 * @param number	number to be converted to it's word representation.
	 * @return String	converted word string from a number
	 */
	public String convert(int number) {
		if(number < 0 || number > 99999) {
			return "Number entered is out of bounds";
		}
		else if (number == 0){
			return "Zero";
		}
		else{
			String input = convertUpto99999(number);
			return input.substring(0, 1).toUpperCase() + input.substring(1);
		}
	}
	
	
	public static void main(String[] args) {
		NumberWords obj = new NumberWords();
	
		int input = 0;
		String param = null;
		try{
			input = Integer.parseInt(args[0]);
			param = args[1];
		}
		catch(Exception ex){
			System.err.println(ex);
		}
		
		if(param.equals("1")){
			System.out.println(Integer.toString(input) + ": " + obj.convert1To10(input));
		}
		else if(param.equals("2")){
			System.out.println(Integer.toString(input) + ": " + obj.convert(input));
		}
		else{
			System.out.println("Check arguments. 2nd argument needs to be 1 or 2.");
		}

	}
	

}