// Project: UnitTests
// Module: phoneletters2digits
// Source code file: GetDigits.java
// The phoneLettersToDigits method of the GetDigits class,
// convert letters to the digits of a phone number.
// The GetDigitsTest class contains unit tests for
// the GetDigits class method.

public class GetDigits {

    static String phoneLettersToDigits(String number) {
        String[ ] letters =
                {"", "", "ABC", "DEF", "GHI", "JKL",
                         "MNO", "PQRS", "TUV", "WXYZ"};

        // Look up each letter in the letters array,
        // the index of the letter is the corresponding
        // digit, which is concatenated to the output
        // string digits.
        String digits = "";
        for(int i = 0; i < number.length( ); i++) {
            char letter = number.charAt(i);
            for(int j = 0; j < letters.length; j++) {
                if(letters[j].indexOf(letter) > -1) {
                    digits += String.valueOf(j);
                    break;
                }
            }
        }
        return digits;
    }
}