CaesarCode

package com.company;

import java.util.Scanner;

public class Main {

    final static String ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        System.out.print("Въведете криптиране (1) или декриптиране (2): ");
        int cryptOrDecrypt = Integer.parseInt(scan.nextLine());

        System.out.print("Въведете код: ");
        int code = Integer.parseInt(scan.nextLine());

        if(cryptOrDecrypt == 1){
            System.out.print("Въведете текст за криптиране: ");
            String input = scan.nextLine();
            System.out.println(crypt(input, code));
        }else{
            System.out.print("Въведете текст за декриптиране: ");
            String input = scan.nextLine();
            System.out.println(decrypt(input, code));
        }
    }

    public static String crypt(String input, int code){
        String cryptedAlphabet = ALPHABET.substring(code) + ALPHABET.substring(0, code);
        String upperInput = input.toUpperCase();
        StringBuilder cryptedInput = new StringBuilder();
        for(int i = 0; i < upperInput.length(); i++){
            for (int j = 0; j < ALPHABET.length(); j++) {
                if(upperInput.toCharArray()[i] == ALPHABET.toCharArray()[j]) cryptedInput.append(cryptedAlphabet.toCharArray()[j]);
            }
        }
        return cryptedInput.toString();
    }

    public static String decrypt(String input, int code){
        String cryptedAlphabet = ALPHABET.substring(code) + ALPHABET.substring(0, code);
        StringBuilder decryptedInput = new StringBuilder();
        for (int i = 0; i < input.length(); i++) {
            for (int j = 0; j < cryptedAlphabet.length(); j++) {
                if(input.toCharArray()[i] == cryptedAlphabet.toCharArray()[j]) decryptedInput.append(ALPHABET.toCharArray()[j]);
            }
        }
        return decryptedInput.toString();
    }
}