fail-encrypt-decrypt

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String input = "aaaaaaaa";
		
		String codes = "slyckies";
        StringBuilder result = new StringBuilder();

        char[] codeList = codes.toCharArray();
        char[] keyList  = input.toCharArray();

        int maxCount = input.length();
        System.out.println("The length is "+maxCount);
        int i = 0;

        for (Character code : codeList) {
            int key = Character.getNumericValue(keyList[i]);
            System.out.println("Process input " + keyList[i] + " (" + key + ") with salt " + code + "(" + ((int) code) + ")");

            if (key % 2 == 0) {
                int res = code+key;
                System.out.println("Output " +  ((int) code) + " + " + key + " = " + res);
                result.append((char)res);
            } else {
                int res = code-key;
                System.out.println("Output " +  ((int) code) + " + " + key + " = " + res);
                result.append((char)res);
            }
            i++;
            if(i>maxCount) {
                i = 0;
            }
        }
        System.out.println("The result is "+result.toString());
         
		// Input is the encrypted result
		String encryptedInput = result.toString();
		keyList = encryptedInput.toCharArray();
		System.out.println("The length is "+keyList.length());
		result = new StringBuilder();
		
		i = 0;
		for (Character code : codeList) {
		
		     int key = Character.getNumericValue(keyList[i]);
		
		     // Create temporary value, to determine it's modulus
		     // Either subtract or add, no problem
		     // Due to (a + a) % 2 or (a - a) % 2 always 0
		     int temp = code + key;
		     if (temp % 2 == 0) {
		         // Switch to substraction
		         int res = code-key;
		         result.append((char)res);
		     } else {
		         // Switch to addition
		         int res = code+key;
		         result.append((char)res);
		     }
		     i++;
		     if (i>maxCount) {
		         i = 0;
		     }
		 }
		 System.out.println("The decryp is "+result.toString());
	}
}