Caesar Cipher

import java.util.*;

public class CaesarCipher

{
    public static void main (String args[]){
        StringBuilder sb = new StringBuilder();
        Scanner reader = new Scanner(System.in);
        System.out.println("Enter a word to encrypt.");
        String word = reader.next().toUpperCase();

        System.out.println("Enter key");
        int key = reader.nextInt();
        int position;
        char character;
        String letters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

        for (int x=0; x<word.length();x++){
            character=word.charAt(x);
            position=letters.indexOf(character);
            position+=key;
            sb.append(letters.charAt(position));
        }

        System.out.println(sb);

    }
}