I would suggest creating a hashtable with the initial
string as the key and the string you wish to convert to as the value. For example, if a converts to t,
Hashtable table = new Hashtable();
table.put("a", "t");
You can then take each letter from the word and us it to extract the value you wish to convert to. For example,
String currentLetter = "a";
String convertedLetter = (String)table.get(currentLetter);
Hope this helps.