Question

For this code after case 0, I need it to ask the user if they would like to see the menu again and some type of if statement or loop to ask them yes or no and if yes print again and if no end program. So it would ask if they would like to see the menu again then ask what their choice is. If yes print menu and if no end program.

import java.util.InputMismatchException;
import java.util.*;
import java.io.*;

public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("Welcome to the Caesar Cipher!\nThis utility will let you encrypt and decrypt a message"
+ " from a file you provide.");
int userChoice = -1;
int cipher = 0;
String file;
String again = "yes";
String message = "";
String menu = "\n" + "Short messages\n" + "Option 1: Encrypt a Message\n" + "Option 2: Decrypt a Message\n"
+ "Long messages\n" + "Option 3: Encrypt a Text File\n" + "Option 4: Decrypt a Text File\n"
+ "Other Functions\n" + "Option 5: Letter Distribution Analysis\n" + "Option 0: Exit Program\n";
while (userChoice != 0) {
if (again.equalsIgnoreCase("yes") || again.equalsIgnoreCase("y")) {
System.out.print(menu);
}
System.out.print("What is your choice?: ");
try {
userChoice = in.nextInt();
in.nextLine();
} catch (InputMismatchException e) {
System.out.println("Input was not a number.");
in.nextLine();
userChoice = -1;
} // make a switch case for the menu

switch (userChoice) {
case 1:// encrypt message

System.out.println("Enter your short message: ");
message = in.nextLine();
cipher = get_num(in);
System.out.println(Caesar.encrypt(message, cipher));
break;

case 2:// decrypt message
System.out.println("Enter your short message: ");
message = in.nextLine();
cipher = get_num(in);
System.out.println(Caesar.decrypt(message, cipher));
break;
case 3:
// encrypt text
file = get_name(in);
if (file.equals("n")) {
break;
} else {
cipher = get_num(in);
message = ReadWrite.read(ReadWrite.open_file(file, in));
ReadWrite.write("Encrypted.txt", Caesar.encrypt(message, cipher));
System.out.println("Encrypted message saved to Encrypted.txt");
}
break;

case 4:// decrypt text
file = get_name(in);
if (file.equals("n")) {
break;
} else {
cipher = get_num(in);
message = ReadWrite.read(ReadWrite.open_file(file, in));
ReadWrite.write("Decrypted.txt", Caesar.decrypt(message, cipher));
System.out.println("Decrypted message saved to Decrypted.txt");
}
break;

case 5:
// letter distribution
String temp = "a";
while (!temp.equalsIgnoreCase("y") && !temp.equalsIgnoreCase("n")) {
System.out.print("Is the message in a file (y/n)?: ");
temp = in.nextLine();
if (temp.equalsIgnoreCase("n")) {
System.out.println("Enter your encrypted message: ");
message = in.nextLine(); // end enter message
} else {
file = get_name(in);
if (file.equals("n")) {
break;
} else {
message = ReadWrite.read(ReadWrite.open_file(file, in));
}
} // end file message
Caesar.printDistr(Caesar.letterDistr(message)); // exit message

}
break;
case 0:
System.out.println("Thank you for using the utility and goodbye~");
break;

default: // invalid input
System.out.println("That wasn't a valid menu option."); // end switch
if (userChoice != 0) {
System.out.print("Would you like to see the menu again?: ");
again = in.nextLine();
  
}
}
} // end while loop menu
in.close();
}// end main method

public static int get_num(Scanner in) {
int num = 0;
while (num < 2 || num > 26) {
try {
System.out.print("What is the cipher?: ");
num = in.nextInt();
in.nextLine();
if (num < 2 || num > 26) {
System.out.println("Cipher must be between 2 and 26 inclusive.");
System.out.print("What is the cipher?: ");
num = in.nextInt();
in.nextLine();
}
} catch (InputMismatchException e) {
System.out.println("You need to use a number for the cipher. Try again.");
break;
}
}
return num;
}// end get_num method

public static String get_name(Scanner in) {
String file;
String temp;
String response;
System.out.print("Enter the name of the text file: ");
file = in.nextLine();
String ext = file.substring(file.length() - 4);
boolean txt = ext.equals(".txt");
if (!txt) {
temp = file + ".txt";
System.out.print("Entered file name doesn't end with \'.txt\' " + "attempting to ammend file extension.\n"
+ "New File name: " + temp + "\n" + "Is this correct? ");
response = in.nextLine();
if (response.equalsIgnoreCase("yes") || response.equalsIgnoreCase("y")) {
return temp;
} else {
System.out.println("Program can only use txt files. Try again.");
return "n";
}
} else {
return file;
}
}//end get_name method
} //end Main

Answer 1

import java.util.InputMismatchException;
import java.util.*;
import java.io.*;

public class Main {
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
System.out.println("Welcome to the Caesar Cipher!\nThis utility will let you encrypt and decrypt a message"
+ " from a file you provide.");
int userChoice = -1;
int cipher = 0;
String file;
String again = "yes";
String message = "";
while (again == "yes") //Added a while loop for repition of the menu untill the user enters no
{
   String menu = "\n" + "Short messages\n" + "Option 1: Encrypt a Message\n" + "Option 2: Decrypt a Message\n"
   + "Long messages\n" + "Option 3: Encrypt a Text File\n" + "Option 4: Decrypt a Text File\n"
   + "Other Functions\n" + "Option 5: Letter Distribution Analysis\n" + "Option 0: Exit Program\n";
   while (userChoice != 0) {
   if (again.equalsIgnoreCase("yes") || again.equalsIgnoreCase("y")) {
   System.out.print(menu);
   }
   System.out.print("What is your choice?: ");
   try {
   userChoice = in.nextInt();
   in.nextLine();
   } catch (InputMismatchException e) {
   System.out.println("Input was not a number.");
   in.nextLine();
   userChoice = -1;
   } // make a switch case for the menu
  
   switch (userChoice) {
   case 1:// encrypt message
  
   System.out.println("Enter your short message: ");
   message = in.nextLine();
   cipher = get_num(in);
   System.out.println(Caesar.encrypt(message, cipher));
   break;
  
   case 2:// decrypt message
   System.out.println("Enter your short message: ");
   message = in.nextLine();
   cipher = get_num(in);
   System.out.println(Caesar.decrypt(message, cipher));
   break;
   case 3:
   // encrypt text
   file = get_name(in);
   if (file.equals("n")) {
   break;
   } else {
   cipher = get_num(in);
   message = ReadWrite.read(ReadWrite.open_file(file, in));
   ReadWrite.write("Encrypted.txt", Caesar.encrypt(message, cipher));
   System.out.println("Encrypted message saved to Encrypted.txt");
   }
   break;
  
   case 4:// decrypt text
   file = get_name(in);
   if (file.equals("n")) {
   break;
   } else {
   cipher = get_num(in);
   message = ReadWrite.read(ReadWrite.open_file(file, in));
   ReadWrite.write("Decrypted.txt", Caesar.decrypt(message, cipher));
   System.out.println("Decrypted message saved to Decrypted.txt");
   }
   break;
  
   case 5:
   // letter distribution
   String temp = "a";
   while (!temp.equalsIgnoreCase("y") && !temp.equalsIgnoreCase("n")) {
   System.out.print("Is the message in a file (y/n)?: ");
   temp = in.nextLine();
   if (temp.equalsIgnoreCase("n")) {
   System.out.println("Enter your encrypted message: ");
   message = in.nextLine(); // end enter message
   } else {
   file = get_name(in);
   if (file.equals("n")) {
   break;
   } else {
   message = ReadWrite.read(ReadWrite.open_file(file, in));
   }
   } // end file message
   Caesar.printDistr(Caesar.letterDistr(message)); // exit message
  
   }
   break;
   case 0:
   System.out.println("Thank you for using the utility and goodbye~");
   break;
  
   default: // invalid input
   System.out.println("That wasn't a valid menu option."); // end switch
   if (userChoice != 0) {
   System.out.print("Would you like to see the menu again? (yes/no): "); //ADDED (yes/no)
   again = in.nextLine();
  
   }
   }
   } // end while loop menu
   in.close();
}
  
}
// end main method

public static int get_num(Scanner in) {
int num = 0;
while (num < 2 || num > 26) {
try {
System.out.print("What is the cipher?: ");
num = in.nextInt();
in.nextLine();
if (num < 2 || num > 26) {
System.out.println("Cipher must be between 2 and 26 inclusive.");
System.out.print("What is the cipher?: ");
num = in.nextInt();
in.nextLine();
}
} catch (InputMismatchException e) {
System.out.println("You need to use a number for the cipher. Try again.");
break;
}
}
return num;
}// end get_num method

public static String get_name(Scanner in) {
String file;
String temp;
String response;
System.out.print("Enter the name of the text file: ");
file = in.nextLine();
String ext = file.substring(file.length() - 4);
boolean txt = ext.equals(".txt");
if (!txt) {
temp = file + ".txt";
System.out.print("Entered file name doesn't end with \'.txt\' " + "attempting to ammend file extension.\n"
+ "New File name: " + temp + "\n" + "Is this correct? ");
response = in.nextLine();
if (response.equalsIgnoreCase("yes") || response.equalsIgnoreCase("y")) {
return temp;
} else {
System.out.println("Program can only use txt files. Try again.");
return "n";
}
} else {
return file;
}
}//end get_name method
} //end Main