Question

1. Finish the following java question:  Modify a Encryption program so that it uses the following encryption algorithm:

   • Every letter (both uppercase and lowercase) converted to its successor except z and Z, which are converted to 'a' and 'A' respectively (i.e., a to b, b to c, …, y to z, z to a, A to B, B to C, …, Y to Z, Z to A)

   • Every digit converted to its predecessor except 0, which is converted to 9 (i.e., 9 to 8, 8 to 7, … 1 to 0, 0 to 9)

   • Everything else unchanged.

Note:

• You must modify the specifications (API) of the methods involved as well.  

Answer 1

Code For Above Problem:

import java.util.Scanner;

public class Encryption1 {

        public static void main(String[] args) {
                Scanner sc = new Scanner(System.in);
                System.out.println("Enter message to encrypt: ");
                String message = sc.nextLine();
                String result = encrypt(message);
                System.out.println("Encrypted Message is: \n" + result);
                sc.close();
        }

        // Method to encrypt the message
        public static String encrypt(String message) {
                // Create StringBuffer Object to hold encrypted message
                StringBuffer result = new StringBuffer();
                // for all letters in message
                for (int i = 0; i < message.length(); i++) {
                        // take the current character
                        char current = message.charAt(i);

                        // if current character is Uppercase
                        // converted to its successor
                        if (current >= 'A' && current <= 'Z') {
                                // if current character is UpperCase 'Z'
                                // add the 'A' to result
                                if (current == 'Z') {
                                        result.append('A');
                                }
                                // Otherwise add its successor to result
                                else {
                                        result.append((char) (current + 1));
                                }
                        }
                        // if current character is lowercase
                        // converted to its successor
                        else if (current >= 'a' && current <= 'z') {
                                // if current character is UpperCase 'z'
                                // add the 'a' to result
                                if (current == 'z') {
                                        result.append('a');
                                }
                                // Otherwise add its successor to result
                                else {
                                        result.append((char) (current + 1));
                                }
                        }
                        // if current character is digit
                        // converted to its predecessor except 0
                        else if (current >= '0' && current <= '9') {
                                // if current character is digit '0'
                                // add the '9' to result
                                if (current == '0') {
                                        result.append('9');
                                }
                                // Otherwise add its predecessor to result
                                else {
                                        result.append((char) (current - 1));
                                }
                        } else {//if any other character add to result
                                result.append(current);
                        }
                }
                //return result as String
                return result.toString();
        }

}

Sample Run Results:

Enter message to encrypt: 
AbZikd12 Kowlu091
Encrypted Message is: 
BcAjle01 Lpxmv980

Images Of Code;

Image Of Sample Run Results: