Question

I'm stuck in my homework which is about a caesar cipher java program which includes an infinite while loop, char array, and a switch statement

I have to encode and decode messages

Answer 1

public class Main

{

public static int checkCharacter(char ch) {

if (Character.isUpperCase(ch)) {

return 1;

} else if (Character.isLowerCase(ch)) {

return 2;

} else {

return 3;

}

}

public static String encrypt(char chars[], int s)

{

StringBuffer result = new StringBuffer();

char ch;

int i = 0;

while(true)

{

if (i >= chars.length) {

break;

}

switch(checkCharacter(chars[i])) {

case 1:

ch = (char)(((int)chars[i] + s - 65) % 26 + 65);

result.append(ch);

break;

case 2:

ch = (char)(((int)chars[i] + s - 97) % 26 + 97);

result.append(ch);

break;

default:

break;

}

i ++;

}

return result.toString();

}

public static String decrypt(char chars[], int s)

{

StringBuffer result = new StringBuffer();

char ch;

int i = 0;

while(true)

{

if (i >= chars.length) {

break;

}

switch(checkCharacter(chars[i])) {

case 1:

ch = (char)(((int)chars[i] - s + 65) % 26 + 65);

result.append(ch);

break;

case 2:

ch = (char)(((int)chars[i] - s + 97) % 26 + 97);

result.append(ch);

break;

default:

break;

}

i ++;

}

return result.toString();

}

public static void main(String[] args)

{

String text = "ATTACKATONCE";

int s = 4;

System.out.println("Text : " + text);

String encrypted = encrypt(text.toCharArray(), s);

String decrypted = decrypt(encrypted.toCharArray(), s);

System.out.println("Encrypted text: " + encrypted);

System.out.println("Decrypted text: " + decrypted);

}

}