Problem-Solving-And-Answer-in-java/OddEvenCaesar.java at master · afiqiqmal/Problem-Solving-And-Answer-in-java · GitHub

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import java.util.*;
import java.io.*;

//http://programmingcode4life.blogspot.my/

//ODD EVEN Caesar Cipher
public class OddEvenCaesar{

    public static void main(String[] args){
      System.out.print(Encode("Saya makan nasi",5));
      System.out.print(Decode("Xvdv hfffi ifnn",5));
      DecodeNoKey("Xvdv hfffi ifnn");
    }

    public static String Encode(String enc, int offset) {
        offset = offset % 26;
        StringBuilder encoded = new StringBuilder();

        int count =0;

        for (char i : enc.toCharArray()) {
            if(count%2 == 0){
               if (Character.isLetter(i)) {
                   if (Character.isUpperCase(i)) {
                       encoded.append((char) ('A' + (i - 'A' + offset) % 26 ));
                   } else {
                       encoded.append((char) ('a' + (i - 'a' + offset) % 26 ));
                   }
               } else {
                   encoded.append(i);
               }
            }
            else if(count%2 == 1){
               if (Character.isLetter(i)) {
                   if (Character.isUpperCase(i)) {
                       encoded.append((char) ('A' + (i - 'A' + 26-offset) % 26 ));
                   } else {
                       encoded.append((char) ('a' + (i - 'a' + 26-offset) % 26 ));
                   }
               } else {
                   encoded.append(i);
               }
            }

            count++;
        }
        return encoded.toString();
    }

    public static String Decode(String enc, int offset) {
        offset = offset % 26;
        StringBuilder decoded = new StringBuilder();

        int count =0;

        for (char i : enc.toCharArray()) {
            if(count%2 == 1){
               if (Character.isLetter(i)) {
                   if (Character.isUpperCase(i)) {
                       decoded.append((char) ('A' + (i - 'A' + offset) % 26 ));
                   } else {
                       decoded.append((char) ('a' + (i - 'a' + offset) % 26 ));
                   }
               } else {
                   decoded.append(i);
               }
            }
            else if(count%2 == 0){
               if (Character.isLetter(i)) {
                   if (Character.isUpperCase(i)) {
                       decoded.append((char) ('A' + (i - 'A' + 26-offset) % 26 ));
                   } else {
                       decoded.append((char) ('a' + (i - 'a' + 26-offset) % 26 ));
                   }
               } else {
                   decoded.append(i);
               }
            }

            count++;
        }
        return decoded.toString();
    }

    public static void DecodeNoKey(String enc) {

        for(int x=0;x<26;x++){
           int offset = x % 26;
           StringBuilder decoded = new StringBuilder();

           int count =0;

           for (char i : enc.toCharArray()) {
               if(count%2 == 1){
                  if (Character.isLetter(i)) {
                      if (Character.isUpperCase(i)) {
                          decoded.append((char) ('A' + (i - 'A' + offset) % 26 ));
                      } else {
                          decoded.append((char) ('a' + (i - 'a' + offset) % 26 ));
                      }
                  } else {
                      decoded.append(i);
                  }
               }
               else if(count%2 == 0){
                  if (Character.isLetter(i)) {
                      if (Character.isUpperCase(i)) {
                          decoded.append((char) ('A' + (i - 'A' + 26-offset) % 26 ));
                      } else {
                          decoded.append((char) ('a' + (i - 'a' + 26-offset) % 26 ));
                      }
                  } else {
                      decoded.append(i);
                  }
               }

               count++;
           }
           System.out.println(decoded.toString());
       }
    }

}