Decoder Solution

import java.io.IOException;

public class Decoder
{
    public static String encrypt(String phrase, String key)
    {
        String result = "";
        for (int i = 0; i < phrase.length(); i++)
        {
            char let = encryptLetter(phrase.charAt(i), key);
            result += let;
        }
        return result;

    }

    public static String decrypt(String phrase, String key)
    {
        String result = "";
        for (int i = 0; i < phrase.length(); i++)
        {
            char ch = decryptLetter(phrase.charAt(i), key);
            result += ch;
        }
        return result;

    }

    public static char encryptLetter(char letter, String key)
    {
        char result = ' ';
        if (Character.isLetter(letter))
        {
            result = key.charAt(Character.toUpperCase(letter) - 'A');
        }
        return result;
    }

    public static char decryptLetter(char letter, String key)
    {
        int index = key.indexOf(letter);
        if (index != -1)
        {
            letter = (char) ('A' + index);
        }
        return letter;
    }

    public static void main(String[] args) throws IOException
    {
        String startSeq = "xv fpu vot ipk nk chpwindvoth tqeyditi";
        String plaintext = "";
        String ciphertext = "";
        String keySeq = "prjitgcoxbsynwdemhuvlzfqka";
        plaintext = decrypt(startSeq, keySeq);
        System.out.println("Decoded text is " + plaintext);
        ciphertext = encrypt(plaintext, keySeq);
        System.out.println("Encoded text is " + ciphertext);

    }

}