CODEWITHSUNDEEP
javaencryptioncaesar-cipher
Ibrahim
Ibrahim

Reputation: 1

encryption using Caesar Cipher with given methods..Java

Am trying to create a method to encrypt a word with Caesar cipher here is the code:

public static void main (String [] args)
{

    String s = "ahmed";
    int k = 2;
    char[] c = new char[5];
    int[] a = new int[s.length()];
    for (int i = 0; i<s.length();i++){

       a[i] = Secret_Code_Library.getDigit(s.charAt(i));
       a[i] = i + k ;
       c[i] = Secret_Code_Library.getLetter(a[i]);

    }                           
    String ss = String.valueOf(c);
}

Secret_Code_Library is a class that contains the two methods (getDigit(char): returns the number of the character a =0, b= 1...etc, and getLetter(int): returns the letter corresponding to the number). my problem is when ever i try to encrypt a word it encrypts only the first letter correctly and save it in to the array a. P.S: I have to use those two methods.

the output of the above code is: cdefg
while it should be: cjogf this is the class :

public class Secret_Code_Library {


public static final char [] LETTERS={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z' };


public static char getLetter(int digit){
   return  LETTERS[digit];   }
    public static int getDigit(char ch){
    int digit=0;
    switch (ch){
        case 'A': digit=0; break;   case 'B': digit=1; break; case 'C': digit=2; break; 
        case 'D': digit=3; break;   case 'E': digit=4; break; case 'F': digit=5; break;    
        case 'G': digit=6; break;   case 'H': digit=7; break; case 'I':  digit=8; break;           
        case 'J':  digit=9; break;   case 'K': digit=10; break; case 'L': digit=11; break;    
        case 'M': digit=12; break; case 'N': digit=13; break;  case 'O': digit=14; break;    
        case 'P': digit=15; break; case 'Q': digit=16; break;   case 'R': digit=17; break;    
        case 'S': digit=18; break; case 'T': digit=19; break;   case 'U': digit=20; break;
        case 'V': digit=21; break; case 'W': digit=22; break;  case 'X': digit=23; break;    
        case 'Y': digit=24; break; case 'Z': digit=25; break;      
 }// switch
    return digit;
}}

Upvotes: 0

Views: 599

Answers (1)

Artjom B.
Artjom B.

Reputation: 61902

a[i]= i + k ;

should be

a[i] = a[i] + k;

because you're not adding the key to the position of the current encrypted character, but the integer value of the character itself.

But that is not enough. What happens when you're encrypting 'z' with k = 2? You should wrap around in the alphabet, if the Secret_Code_Library.getLetter(a[i]); doesn't already do this for you.

If your alphabet is 26 characters long, then this should do it:

a[i] = (a[i] + k) % 26;

Upvotes: 3

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