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package ciphers;
import java.util.Scanner;
/**
* A Java implementation of Caesar Cipher. /It is a type of substitution cipher in which each letter
* in the plaintext is replaced by a letter some fixed number of positions down the alphabet. /
*
* @author FAHRI YARDIMCI
* @author khalil2535
*/
public class Caesar {
/**
* Encrypt text by shifting every Latin char by add number shift for ASCII Example : A + 1 -> B
*
* @param message
* @param shift
* @return Encrypted message
*/
public static String encode(String message, int shift) {
String encoded = "";
shift %= 26;
final int length = message.length();
for (int i = 0; i < length; i++) {
// int current = message.charAt(i); //using char to shift characters because ascii
// is in-order latin alphabet
char current = message.charAt(i); // Java law : char + int = char
if (IsCapitalLatinLetter(current)) {
current += shift;
encoded += (char) (current > 'Z' ? current - 26 : current); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
current += shift;
encoded += (char) (current > 'z' ? current - 26 : current); // 26 = number of latin letters
} else {
encoded += current;
}
}
return encoded;
}
/**
* Decrypt message by shifting back every Latin char to previous the ASCII Example : B - 1 -> A
*
* @param encryptedMessage
* @param shift
* @return message
*/
public static String decode(String encryptedMessage, int shift) {
String decoded = "";
shift %= 26;
final int length = encryptedMessage.length();
for (int i = 0; i < length; i++) {
char current = encryptedMessage.charAt(i);
if (IsCapitalLatinLetter(current)) {
current -= shift;
decoded += (char) (current < 'A' ? current + 26 : current); // 26 = number of latin letters
} else if (IsSmallLatinLetter(current)) {
current -= shift;
decoded += (char) (current < 'a' ? current + 26 : current); // 26 = number of latin letters
} else {
decoded += current;
}
}
return decoded;
}
/**
* @param c
* @return true if character is capital Latin letter or false for others
*/
private static boolean IsCapitalLatinLetter(char c) {
return c >= 'A' && c = 'a' && c