Step by Step solution about How to resolve the algorithm Caesar cipher step by step in the Java programming language

Overview: The Java program defines a utility class called Cipher for performing character substitution encoding and decoding. It demonstrates how to encode and decode a given string using a shift cipher technique.

Class Definition:

• The Cipher class is declared as public with a main method to execute the program.

Encoding Method (encode):

• The encode method takes two parameters:
  • enc: The input string to be encoded.
  • offset: The character offset used for encoding.
• It computes the adjusted offset by taking the modulus of offset by 26 and adding 26, ensuring it stays within the range of 0 to 25.
• It creates a StringBuilder called encoded to construct the encoded string.
• The method iterates through each character (i) in the input string.
• For each character, it checks if it's a letter. If it is, it further checks if it's uppercase or lowercase.
• If the character is a letter, it calculates the shifted character by adding the offset to its position in the alphabet ('A' for uppercase or 'a' for lowercase). The result is then taken modulo 26 to wrap around the alphabet.
• If the character is not a letter, it is appended unchanged.
• After processing all characters, the encoded string is returned.

Decoding Method (decode):

• The decode method is a straightforward wrapper around the encode method.
• It takes the encoded string (enc) and a decoding offset and calls encode with the same string but a reversed offset (26 minus the decoding offset).
• The result of encode is the decoded string.

Main Method:

• In the main method:
  • It defines an input string (str) containing a sentence.
  • It encodes the string using a shift of 12 characters and prints the encoded result.
  • It then decodes the encoded string using the same shift of 12 characters and prints the decoded result.

How it Works:

• The encode method implements the Caesar Cipher, which is a shift cipher that replaces each character in a given text with another character a fixed number of positions down the alphabet.
• The decode method reverses the substitution by using the same shift value but in the opposite direction, effectively returning the original plaintext.
• The program demonstrates the shift cipher encryption and decryption process, showing how the input string is encoded and then decoded back to its original form.

public class Cipher {
    public static void main(String[] args) {

        String str = "The quick brown fox Jumped over the lazy Dog";

        System.out.println( Cipher.encode( str, 12 ));
        System.out.println( Cipher.decode( Cipher.encode( str, 12), 12 ));
    }

    public static String decode(String enc, int offset) {
        return encode(enc, 26-offset);
    }

    public static String encode(String enc, int offset) {
        offset = offset % 26 + 26;
        StringBuilder encoded = new StringBuilder();
        for (char i : enc.toCharArray()) {
            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);
            }
        }
        return encoded.toString();
    }
}