Java Convert Numeric Values to English Words Equivalent

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package convertnumbers;

/**
 *
 * @author k
 */

interface ConvertNumbersToWords {

    public void convertNumber(int number);

    public String getNumberValue();

    public void clearValues();

}

public class ConvertNumbers {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        //Your original arrays
        String[] ones = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "teb", "eleven", "twelve", "thirteen",
            "fourteen", "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
        //For this to work properly, you have to have two empty strings for the first two values
        String[] tens = {"", "", "twenty", "thirty", "fourty",
            "fifty", "sixty", "seventy", "eighty", "ninety"};

        /* Anonymous inner class that convert Tens and Ones to the word equivalence
         If you cannot use anonymous Inner classes you can take what is between the { }
         and create a new class the implements the ConvertNumbersToWords interface  */
        ConvertNumbersToWords convertTensAndOnes = new ConvertNumbersToWords() {

            private String numberValue = "";

            @Override
            public void convertNumber(int number) {

                if (number < 20) {
                    numberValue = ones[number];
                } else {

                    String numberString = String.valueOf(number);

                    if (numberString.length() >= 2) {
                        String lastDigit = numberString.substring(numberString.length() - 1);
                        String secondToLastDigit = numberString.substring(numberString.length() - 2, numberString.length() - 1);
                        int lastDigitAsInt = Integer.parseInt(lastDigit);
                        int secondToLastDigitAsInt = Integer.parseInt(secondToLastDigit);
                        numberValue = tens[secondToLastDigitAsInt] + "-"+ ones[lastDigitAsInt];
                    }
                }
            }

            @Override
            public String getNumberValue() {
                return numberValue;
            }

            @Override
            public void clearValues() {
                this.numberValue = "";
            }
        };

        /* anonymous inner class that convert Hundres to the word equivalence, again
         if you cannot use anonymous Inner classes just take what is between the { }
         and create a new class the implements the ConvertNumbersToWords interface  */
        ConvertNumbersToWords convertHundreds = new ConvertNumbersToWords() {

            private String numberValue = "";

            @Override
            public void convertNumber(int number) {
                String numberString = String.valueOf(number);
                if (numberString.length() >= 3) {
                    String hundredsDigitString = numberString.substring(numberString.length() - 3, numberString.length() - 2);
                    int hundredsDigit = Integer.parseInt(hundredsDigitString);
                    numberValue = ones[hundredsDigit];
                }
            }

            @Override
            public String getNumberValue() {
                if (numberValue != null && numberValue.length() > 0) {
                    return numberValue + "-Hundred ";
                } else {
                    return "";
                }
            }

            @Override
            public void clearValues() {
                this.numberValue = "";
            }
        };

        //TODO: create convertThousands anonymous inner class to covert the thousands place its word value


        ConvertNumbersToWords[] convertNumbersToWords = new ConvertNumbersToWords[2];
        convertNumbersToWords[0] = convertTensAndOnes;
        convertNumbersToWords[1] = convertHundreds;
        //TODO: add covertThousands anonymous inner class to ConvertNumbersToWords array

        // Begin Test with a few different numeric values
        int myInt = 242;
        int myInt2 = 9;
        int myInt3 = 998;
        int myInt4 = 47;

        StringBuilder sb = new StringBuilder();
        for (int i = (convertNumbersToWords.length - 1); i >= 0; i--) {
            convertNumbersToWords[i].convertNumber(myInt);
            sb.append(convertNumbersToWords[i].getNumberValue());
        }
        System.out.println(sb.toString());

        sb = new StringBuilder();
        for (int i = (convertNumbersToWords.length - 1); i >= 0; i--) {
            convertNumbersToWords[i].clearValues();
            convertNumbersToWords[i].convertNumber(myInt2);
            sb.append(convertNumbersToWords[i].getNumberValue());
        }
        System.out.println(sb.toString());

        sb = new StringBuilder();
        for (int i = (convertNumbersToWords.length - 1); i >= 0; i--) {
            convertNumbersToWords[i].clearValues();
            convertNumbersToWords[i].convertNumber(myInt3);
            sb.append(convertNumbersToWords[i].getNumberValue());
        }
        System.out.println(sb.toString());

        sb = new StringBuilder();
        for (int i = (convertNumbersToWords.length - 1); i >= 0; i--) {
            convertNumbersToWords[i].clearValues();
            convertNumbersToWords[i].convertNumber(myInt4);
            sb.append(convertNumbersToWords[i].getNumberValue());
        }
        System.out.println(sb.toString());
        //End Test

    }

}