Below you will find me using toCharArray in order to send a string to array. I then MOVE the value of the letter using a for statement...

for(i = 0; i < letter.length; i++){
               letter[i] += (shiftCode);
               System.out.print(letter[i]);
            }

However, when I use shiftCode to move the value such as...

a shifted by -1; I get a symbol @. Is there a way to send the string to shiftCode or tell shiftCode to ONLY use letters? I need it to see my text, like "aaron", and when I use the for statement iterate through a-z only and ignore all symbols and numbers. I THINK it is as simple as...

letter=codeWord.toCharArray(a,z);

But trying different forms of that and googling it didn't give me any results. Perhaps it has to do with regex or something? Below you will find a complete copy of my program; it works exactly how I want it to do; but it iterates through letters and symbols. I also tried finding instructions online for toCharArray but if there exists any arguments I can't locate them.

My program...

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

/*
 * Aaron L. Jones
 * CS219
 * AaronJonesProg3
 * 
 * This program is designed to -
 * Work as a Ceasar Cipher
 */

/**
 *
 * Aaron Jones
 */
public class AaronJonesProg3 {
    static String codeWord;
    static int shiftCode;
    static int i;
    static char[] letter;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        // Instantiating that Buffer Class
        // We are going to use this to read data from the user; in buffer
        // For performance related reasons
        BufferedReader reader;

        // Building the reader variable here
        // Just a basic input buffer (Holds things for us)
        reader = new BufferedReader(new InputStreamReader(System.in));

        // Java speaks to us here / We get it to query our user
        System.out.print("Please enter text to encrypt: ");

        // Try to get their input here
        try {    
            // Get their codeword using the reader
            codeWord = reader.readLine();

            // Make that input upper case
            codeWord = codeWord.toUpperCase();
            // Cut the white space out
            codeWord = codeWord.replaceAll("\\s","");
            // Make it all a character array
            letter = codeWord.toCharArray();
        }
        // If they messed up the input we let them know here and end the prog.
        catch(Throwable t) {
            System.out.println(t.toString());
            System.out.println("You broke it. But you impressed me because"
                    + "I don't know how you did it!");
        }

        // Java Speaks / Lets get their desired shift value
        System.out.print("Please enter the shift value: ");

        // Try for their input
        try {
               // We get their number here
               shiftCode = Integer.parseInt(reader.readLine());
        }
        // Again; if the user broke it. We let them know.
        catch(java.lang.NumberFormatException ioe) {
            System.out.println(ioe.toString());
            System.out.println("How did you break this? Use a number next time!");
        }

        for(i = 0; i < letter.length; i++){
           letter[i] += (shiftCode);
           System.out.print(letter[i]);
        }

        System.out.println();

        /****************************************************************
         ****************************************************************
         ***************************************************************/
        // Java speaks to us here / We get it to query our user
        System.out.print("Please enter text to decrypt: ");

        // Try to get their input here
        try {    
            // Get their codeword using the reader
            codeWord = reader.readLine();

            // Make that input upper case
            codeWord = codeWord.toUpperCase();
            // Cut the white space out
            codeWord = codeWord.replaceAll("\\s","");
            // Make it all a character array
            letter = codeWord.toCharArray();
        }
        // If they messed up the input we let them know here and end the prog.
        catch(Throwable t) {
            System.out.println(t.toString());
            System.out.println("You broke it. But you impressed me because"
                    + "I don't know how you did it!");
        }

        // Java Speaks / Lets get their desired shift value
        System.out.print("Please enter the shift value: ");

        // Try for their input
        try {
               // We get their number here
               shiftCode = Integer.parseInt(reader.readLine());
        }
        // Again; if the user broke it. We let them know.
        catch(java.lang.NumberFormatException ioe) {
            System.out.println(ioe.toString());
            System.out.println("How did you break this? Use a number next time!");
        }

        for(i = 0; i < letter.length; i++){
           letter[i] += (shiftCode);
           System.out.print(letter[i]);
        }

        System.out.println();
    }
}