UPDATE:
The final version of my utility looks like this:
StringBuilder b = new StringBuilder();
for(char c : inLetters.toLowerCase(
How about simply:
String convert(String inLetters) {
String digits = "22233344455566677778889999";
String alphas = "abcdefghijklmnopqrstuvwxyz";
String result = "";
for (char c : inLetters.toLowerCase().toCharArray()) {
int pos = alphas.indexOf(c);
result += (pos == -1 ? c : digits.charAt(pos));
}
return result;
}