Using only alphanumeric characters(a-z) inside toCharArray

Question

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();
    }
}

Please do not ever use this: catch(Throwable t). Catch (and handle!) only the type of exception that is required. — Natix
– Natix, Commented Sep 8, 2012 at 17:51
Can you explain why please? Or link me to an explanation? I would love to understand how to handle exceptions better. — ILikeTurtles
– ILikeTurtles, Commented Sep 8, 2012 at 18:21
java.dzone.com/news/the-curse-swallowed-exception, onjava.com/pub/a/onjava/2003/11/19/exceptions.html, today.java.net/pub/a/today/2006/04/06/… — Natix
– Natix, Commented Sep 8, 2012 at 19:31
Your code has an entire section apparently repeated. Is this deliberate? If so, is it necessary to an explanation of the problem? — Stewart
– Stewart, Commented Mar 27, 2014 at 9:45

Kumar Vivek Mitra · Accepted Answer · 2012-09-08 17:48:40Z

2

Use Character.isLetter() to separate out the Letters.......

See this link.....

http://docs.oracle.com/javase/1.4.2/docs/api/java/lang/Character.html

Eg:

public class Test{
   public static void main(String args[]){
      System.out.println( Character.isLetter('c'));
      System.out.println( Character.isLetter('5'));
   }
}

Output:

true false

answered Sep 8, 2012 at 17:48

Kumar Vivek Mitra

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1 Comment

ILikeTurtles Over a year ago

This didn't work for me; but I am pretty sure it could have worked. Up voting in case someone else takes this path. Thank you.

Community · Accepted Answer · 2017-05-23 11:49:07Z

1

First check each character of the array with if(Character.isLetter(letter[i])). Then with your shiftcode, check the difference between the character at letter[i] with corresponding last alphabet character i.e. uppercase or a lowercase 'z'. For a detailed explanation, see my answer for a caesar cipher at this link in this forum.

edited May 23, 2017 at 11:49

CommunityBot

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answered Sep 8, 2012 at 17:54

Victor Mukherjee

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1 Comment

ILikeTurtles Over a year ago

This worked. Sort of. I didn't use isLetter; but after seeing your use of the number 26 it led me to another website that eventually gave me the answer I wanted. Upvoting this for the lead.

ILikeTurtles · Accepted Answer · 2012-09-09 05:34:15Z

0

        // iterating
    for(i = 0; i < letter.length; i++){
        letter[i] += (shiftCode); // Start adding shiftcode to letter
        if(!(letter[i] <= 'Z')) {
            // if its bigger than Z subtract 26
            letter[i] -= (26);
        }
        // less than A?
        if(!(letter[i] >= 'A')) {
            // add 26
            letter[i] += (26);
        }
        System.out.print(letter[i]); // print it all out
    }

The above code is the correct answer to my problem. I discovered that UNICODE is numbered and by using the number 26 we could move about PRETTY well if you don't go hog wild with choosing a large number. I think a smart thing to do would be to program in a catch that forces the user to only iterate by up to -26 to 26.

answered Sep 9, 2012 at 5:34

ILikeTurtles

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1 Comment

Stewart Over a year ago

I find it funny to read the mix of char and int types. You could do it using the fact that ('Z' - 'A') == 25 e.g. final char ADJUST = ('Z' - 'A') + 1; then use ADJUST in your for loop.

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