Character Combination For Numbers

Question: Suppose you represent every number with a character like
0 –> a, 1 –> b, 2 –> c, ………………24 –> y, 25 –> z

Now given a number, give words combinations for it.

Example: 1234
=> 1-2-3-4, 12-2-4, 1-23-4
=> bcde, mde, bxe

Java code for simple backtracking approach : 

public class CharCombinationWithNumbers {

 private static char[] alphabet = "abcdefghijklmnopqrstyuvxyz".toCharArray();

 public static void main(String[] args) {
  printPossibilities("", "1234");
 }

 private static void printPossibilities(String partialString, String string) {
  if (string == null || string.length() < 1) {
   System.out.println(partialString);
   return;
  }
  int digit = Integer.parseInt(string.substring(0, 1));
  printPossibilities(partialString + alphabet[digit], string.substring(1));
  if (string.length() > 1) {
   digit = Integer.parseInt(string.substring(0, 2));
   if (digit >= 10 && digit < alphabet.length) {
    printPossibilities(partialString + alphabet[digit], string
      .substring(2));
   }
  }
 }
}

Refer : http://tech-queries.blogspot.com/2011/03/character-combination-for-numbers.html