I have below question and I have my code as well. My program asks for all the command line user inputs. How can I fix my code to have a user input keyword, take an input plaintext file and output a ciphertext as file?

My Java program which asks command line inputs:

import java.util.*;

public class SubstitutionCipher { private static final String ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; public static void main(String[] args) { Scanner scan = new Scanner(System.in); System.out.print("Enter a keyword: "); String keyword = scan.nextLine(); //scan.close(); String key = generateKey(keyword); System.out.println("Key: " + key); System.out.print("Enter a message to encrypt: "); scan = new Scanner(System.in); String message = scan.nextLine(); //scan.close(); String encryptedMessage = encrypt(message, key); System.out.println("Encrypted message: " + encryptedMessage); String decryptedMessage = decrypt(encryptedMessage, key); System.out.println("Decrypted message: " + decryptedMessage); } private static String generateKey(String keyword) { StringBuilder sb = new StringBuilder(); Set used = new HashSet(); for (char c : keyword.toCharArray()) { if (!used.contains(c)) { sb.append(c); used.add(c); } } for (char c = 'Z'; c >= 'A'; c--) { if (!used.contains(c)) { sb.append(c); } } return sb.toString(); } private static String encrypt(String message, String key) { message = message.toUpperCase(); StringBuilder sb = new StringBuilder(); for (char c : message.toCharArray()) { int index = ALPHABET.indexOf(c); if (index != -1) { sb.append(key.charAt(index)); } else { sb.append(c); } } return sb.toString(); } private static String decrypt(String message, String key) { message = message.toUpperCase(); StringBuilder sb = new StringBuilder(); for (char c : message.toCharArray()) { int index = key.indexOf(c); if (index != -1) { sb.append(ALPHABET.charAt(index)); } else { sb.append(c); } } return sb.toString(); } }

2 Task Two: The Substitution cipher (2 marks) A substitution cipher by a keyword works as follows. If a keyword is "STRAWBERRY", we remove the repeating characters in it to get "STRAWBEY". Then, we append the rest of the alphabet characters in reverse order (from ' Z ' to ' A ') to the keyword to construct a key i.e., "STRAWBEYZXVUQPONMLKJIHGFDC" to form a complete substitution key. Finally, we encrypt amessage by substituting its characters with the characters in the key as follows: Your task is to implement the substitution cipher. In particular, your program should - be a command-line program; - take a keyword, which is typed through command-line interface, as input; 2 - take a plaintext (message) file as input; - output a ciphertext as a file; - take a ciphertext file as input; - output a plaintext as a file; - handle any possible errors; - Write in C/C++ or Java (or else, you need to consult Mr Sionggo); - be submitted with a clear readme.txt file. NB: Ignore case. That is, you can choose whether you will input and output uppercase or lowercase characters. Also, keep (do not encrypt) special character such as full stops and commas