Cipher — Hive

import java.util.stream.*;

public class Cipher {

private String key;

public Cipher() {

    this("aaaaaaaaaa");

}

public Cipher(String key) {

    this.key = key;

}

public String getKey() {

    return key;

}

public String encode(String plainText) {

    return shift(plainText, false);

}

public String decode(String cipherText) {

    return shift(cipherText, true);

}

private String shift(String plainText, boolean down){

    StringBuilder result = new StringBuilder();

    for(int i=0; i<plainText.length(); i++){

        char currentLett = plainText.charAt(i);

        int transform = (down? -1: 1) \* (key.charAt(i% key.length()) - 'a');

        int newTrasf = ((currentLett - 'a' + transform)+26)% 26 + 'a';

        result.append((char) newTrasf);

    }

    return result.toString();

}

}