algorithm/Java
1
0
Fork 0
mirror of https://github.com/TheAlgorithms/Java.git synced 2025-07-07 09:45:04 +08:00
Code Issues Packages Projects Releases Wiki Activity

Merge pull request #412 from khalil2535/master

Browse Source 
Update Caesar.java
This commit is contained in:
Christian Bender
2018-04-13 00:34:53 +02:00
committed by GitHub
parent f808a2b217 ca8f6dbb38
commit 2d5a9b1f60
1 changed files with 125 additions and 111 deletions
Download Patch File Download Diff File Expand all files Collapse all files

236
ciphers/Caesar.java
View File

@ -1,117 +1,131 @@
/**
Author : FAHRI YARDIMCI
package ciphers;
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. /
**/
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 {
public static String encode (String message,int shift)
{
String encoded = "";
for(int i = 0 ; i<message.length() ;i++)
{
int current = message.charAt(i); //using char to shift characters because ascii is in-order latin alphabet
if(current==32)
{
encoded += " ";
continue;
}
else if (current>=65 && current<= 90)
{
int numAlphabet = message.charAt(i);
if(shift + numAlphabet > 90)
{
int j = 90 - numAlphabet;
char nextKey = (char)(65 + (shift - j - 1));
encoded += nextKey;
}
else
{
char nextKey = (char)(current + shift);
encoded += nextKey;
}
}
else if (current>=97 && current <= 122)
{
int numAlphabet = message.charAt(i);
if(shift + numAlphabet > 122)
{
int j = 122 - numAlphabet;
char nextKey = (char)(97 + (shift - j - 1));
encoded += nextKey;
}
else
{
char nextKey = (char)(current + shift);
encoded += nextKey;
}
}
}
return encoded;
}
public static String decode (String message,int shift)
{
String decoded = "";
for(int i = 0 ; i<message.length() ;i++)
{
int current = message.charAt(i);
if(current==32)
{
decoded += " ";
continue;
/**
* 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 = "";
}
else if (current>=65 && current<= 90)
{
int numAlphabet = message.charAt(i);
if(numAlphabet - shift < 65)
{
int j = numAlphabet - 65;
char nextKey = (char)(90 - (shift - j - 1));
decoded += nextKey;
}
else
{
char nextKey = (char)(current - shift);
decoded += nextKey;
}
}
else if (current>=97 && current <= 122)
{
int numAlphabet = message.charAt(i);
if(numAlphabet - shift < 97)
{
int j = numAlphabet - 97;
char nextKey = (char)(122 - (shift - j - 1));
decoded += nextKey;
}
else
{
char nextKey = (char)(current - shift);
decoded += nextKey;
}
}
}
return decoded;
}
public static void main(String[] args)
{
Scanner input = new Scanner(System.in);
System.out.println("Please enter the message (Latin Alphabet)");
String message = input.nextLine();
System.out.println(message);
System.out.println("Please enter the shift number");
int shift = input.nextInt() % 26;
System.out.println("(E)ncode or (D)ecode ?");
char choice = input.next().charAt(0);
if(choice == 'E' || choice=='e')
System.out.println("ENCODED MESSAGE IS \n" + encode(message,shift)); //send our function to handle
if(choice =='D' || choice =='d')
System.out.println("DECODED MESSAGE IS \n" + decode(message,shift));
}
while (shift >= 26) { // 26 = number of latin letters
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 = "";
while (shift >= 26) { // 26 = number of latin letters
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 <= 'Z';
}
/**
*
* @param c
* @return true if character is small Latin letter or false for others
*/
private static boolean IsSmallLatinLetter(char c) {
return c >= 'a' && c <= 'z';
}
/**
*
* @deprecated TODO remove main and make JUnit Testing
*/
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Please enter the message (Latin Alphabet)");
String message = input.nextLine();
System.out.println(message);
System.out.println("Please enter the shift number");
int shift = input.nextInt() % 26;
System.out.println("(E)ncode or (D)ecode ?");
char choice = input.next().charAt(0);
switch (choice) {
case 'E':
case 'e':
System.out.println("ENCODED MESSAGE IS \n" + encode(message, shift)); //send our function to handle
break;
case 'D':
case 'd':
System.out.println("DECODED MESSAGE IS \n" + decode(message, shift));
}
}
}