This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
The variable 'new_letter' is a char primative. Primative values are not objects, they have no member variables or methods. Perhaps you meant to us the Character wrapper class? Perhaps... new_letter = Character.toLowerCase( letters[(int)x] );