Convert a number (english number) to word / text

Introduction:
This program is going to convert a number (English number) to word / text by making a sentence of it.
For example:

0	zero
1	one
16	sixteen
100	one hundred
118	one hundred eighteen
200	two hundred
219	two hundred nineteen
800	eight hundred
801	eight hundred one
1316	one thousand three hundred sixteen
1000000	one million
2000000	two million
3000200	three million two hundred
700000	seven hundred thousand
9000000	nine million
9001000	nine million one thousand
123456789	one hundred twenty three million four hundred fifty six thousand seven hundred eighty nine
2147483647	two billion one hundred forty seven million four hundred eighty three thousand six hundred forty seven
3000000010L	three billion ten

Flow chart for convert a number (english number) to word / text
package com.struts2spring;

import java.text.DecimalFormat;

public class EnglishNumberToWords {

	private static final String[] tensNames = { "", " ten", " twenty", " thirty", " forty", " fifty", " sixty", " seventy", " eighty",
			" ninety" };

	private static final String[] numNames = { "", " one", " two", " three", " four", " five", " six", " seven", " eight", " nine", " ten",
			" eleven", " twelve", " thirteen", " fourteen", " fifteen", " sixteen", " seventeen", " eighteen", " nineteen" };

	private static String convertLessThanOneThousand(int number) {
		String soFar;

		if (number % 100 < 20) {
			soFar = numNames[number % 100];
			number /= 100;
		} else {
			soFar = numNames[number % 10];
			number /= 10;

			soFar = tensNames[number % 10] + soFar;
			number /= 10;
		}
		if (number == 0)
			return soFar;
		return numNames[number] + " hundred" + soFar;
	}

	public static String convert(long number) {
		// 0 to 999 999 999 999
		if (number == 0) {
			return "zero";
		}

		String snumber = Long.toString(number);

		// pad with "0"
		String mask = "000000000000";
		DecimalFormat df = new DecimalFormat(mask);
		snumber = df.format(number);

		// XXXnnnnnnnnn
		int billions = Integer.parseInt(snumber.substring(0, 3));
		// nnnXXXnnnnnn
		int millions = Integer.parseInt(snumber.substring(3, 6));
		// nnnnnnXXXnnn
		int hundredThousands = Integer.parseInt(snumber.substring(6, 9));
		// nnnnnnnnnXXX
		int thousands = Integer.parseInt(snumber.substring(9, 12));

		String tradBillions;
		switch (billions) {
		case 0:
			tradBillions = "";
			break;
		case 1:
			tradBillions = convertLessThanOneThousand(billions) + " billion ";
			break;
		default:
			tradBillions = convertLessThanOneThousand(billions) + " billion ";
		}
		String result = tradBillions;

		String tradMillions;
		switch (millions) {
		case 0:
			tradMillions = "";
			break;
		case 1:
			tradMillions = convertLessThanOneThousand(millions) + " million ";
			break;
		default:
			tradMillions = convertLessThanOneThousand(millions) + " million ";
		}
		result = result + tradMillions;

		String tradHundredThousands;
		switch (hundredThousands) {
		case 0:
			tradHundredThousands = "";
			break;
		case 1:
			tradHundredThousands = "one thousand ";
			break;
		default:
			tradHundredThousands = convertLessThanOneThousand(hundredThousands) + " thousand ";
		}
		result = result + tradHundredThousands;

		String tradThousand;
		tradThousand = convertLessThanOneThousand(thousands);
		result = result + tradThousand;

		// remove extra spaces!
		return result.replaceAll("^\\s+", "").replaceAll("\\b\\s{2,}\\b", " ");
	}

	public static void main(String[] args) {
		System.out.println("*** " + EnglishNumberToWords.convert(0));
		System.out.println("*** " + EnglishNumberToWords.convert(1));
		System.out.println("*** " + EnglishNumberToWords.convert(16));
		System.out.println("*** " + EnglishNumberToWords.convert(100));
		System.out.println("*** " + EnglishNumberToWords.convert(118));
		System.out.println("*** " + EnglishNumberToWords.convert(200));
		System.out.println("*** " + EnglishNumberToWords.convert(219));
		System.out.println("*** " + EnglishNumberToWords.convert(800));
		System.out.println("*** " + EnglishNumberToWords.convert(801));
		System.out.println("*** " + EnglishNumberToWords.convert(1316));
		System.out.println("*** " + EnglishNumberToWords.convert(1000000));
		System.out.println("*** " + EnglishNumberToWords.convert(2000000));
		System.out.println("*** " + EnglishNumberToWords.convert(3000200));
		System.out.println("*** " + EnglishNumberToWords.convert(700000));
		System.out.println("*** " + EnglishNumberToWords.convert(9000000));
		System.out.println("*** " + EnglishNumberToWords.convert(9001000));
		System.out.println("*** " + EnglishNumberToWords.convert(123456789));
		System.out.println("*** " + EnglishNumberToWords.convert(2147483647));
		System.out.println("*** " + EnglishNumberToWords.convert(3000000010L));

	}
}