Stuck on an exercise,

Hi

What is the solution to writing a foursquare cipher program in java code including a menu option that allows the user to select from three options (1 to 3) as to start the cipher repeat and finally exit the program, i already have code for the foursquare cipher static method based but it only executes from a command line, as you compile with javac and obtain your class then run it entering plaintext followed by keyword 1 keyword2 then the program executes displaying the encrypted cipher text. Would like to know how to implement a menu to make it more user friendly prompt the user for input instead,if you know what i mean.

Here is what i have got,

import java.util.ArrayList; import java.util.List; /** * Java implementation of the Foursquare cipher. */ public class Foursquare { /** * Alphabet template, excluding Q. */ private static final char[] ALPHABET = "ABCDEFGHIJKLMNOPRSTUVWXYZ".toCharArray(); /** * Alphabet square. */ private static final char[][] ALPHABET_SQUARE = new char[5][5]; /** * Static block to populate the Alphabet Square. */ static { int x = 0, y = 0; for (char c : ALPHABET) { ALPHABET_SQUARE[x][y] = c; x++; if (x == 5) { x = 0; y++; } } } /** * Cleans a plaintext or keyword ready for use in the Foursquare cipher. * @param input the text to clean * @return the clean text */ private static String clean(String input) { input = input.trim().replace(" ", "").replace("Q", "").toUpperCase(); StringBuilder clean = new StringBuilder(); for (char c : input.toCharArray()) { if (Character.getType(c) == Character.UPPERCASE_LETTER) { clean.append(c); } } return clean.toString(); } /** * Generates a 5*5 key table for the specified keyword. * @param keyword the keyword from which to generate the table * @return the newly generated key table */ private static char[][] generateKeyTable(String keyword) { keyword = clean(keyword); char[][] keyTable = new char[5][5]; List used = new ArrayList(); int x = 0, y = 0; for (char c : keyword.toCharArray()) { if (!used.contains(c)) { keyTable[x][y] = c; used.add(c); x++; if (x == 5) { x = 0; y++; if (y == 5) { return keyTable; } } } } for (char c : ALPHABET) { if (!used.contains(c)) { keyTable[x][y] = c; x++; if (x == 5) { x = 0; y++; if (y == 5) { return keyTable; } } } } return keyTable; } /** * Splits a string into two-letter strings (digraphs). * @param plaintext the string to split * @return an array of two-letter strings */ private static String[] split(String plaintext) { if (plaintext.length() % 2 != 0) { plaintext = plaintext + "X"; } String[] pairs = new String[plaintext.length() / 2]; int count = 0; for (int i = 0; i < (plaintext.length() / 2); i++) { pairs[i] = plaintext.substring(count, count + 2); count = count + 2; } return pairs; } /** * Encrypts a plaintext with Foursquare using the two specified keywords. * @param plaintext the text to encrypt * @param keyword1 the first keyword to use * @param keyword2 the second keyword to use * @return the ciphertext */ public static String encrypt(String plaintext, String keyword1, String keyword2) { plaintext = clean(plaintext); String[] pairs = split(plaintext); char[][] keytable1 = generateKeyTable(keyword1); char[][] keytable2 = generateKeyTable(keyword2); char first, second; int xFirst = 0, yFirst = 0, xSecond = 0, ySecond = 0; StringBuilder ciphertext = new StringBuilder(); for (String s : pairs) { first = s.charAt(0); second = s.charAt(1); for (int y = 0; y < 5; y++) { for (int x = 0; x < 5; x++) { if (ALPHABET_SQUARE[x][y] == first) { xFirst = x; yFirst = y; } else if (ALPHABET_SQUARE[x][y] == second) { xSecond = x; ySecond = y; } } } ciphertext.append(keytable1[xSecond][yFirst]).append(keytable2[xFirst][ySecond]); } return ciphertext.toString(); } /** * Decrypts a Foursquare-encrypted ciphertext using the two specified keywords. * @param ciphertext the text to decrypt * @param keyword1 the first keyword to use * @param keyword2 the second keyword to use * @return the plaintext */ public static String decrypt(String ciphertext, String keyword1, String keyword2) { String[] pairs = split(ciphertext); char[][] keytable1 = generateKeyTable(keyword1); char[][] keytable2 = generateKeyTable(keyword2); char first, second; int xFirst = 0, yFirst = 0, xSecond = 0, ySecond = 0; StringBuilder plaintext = new StringBuilder(); for (String s : pairs) { first = s.charAt(0); second = s.charAt(1); for (int y = 0; y < 5; y++) { for (int x = 0; x < 5; x++) { if (keytable1[x][y] == first) { xFirst = x; yFirst = y; } else if (keytable2[x][y] == second) { xSecond = x; ySecond = y; } } } plaintext.append(ALPHABET_SQUARE[xSecond][yFirst]).append(ALPHABET_SQUARE[xFirst][ySecond]); } return plaintext.toString(); } /**maybe at this point a constructor could be intansiated or a runner class that can give a menu twist to the program **/ public static void main(String[] args) { try { if(args[0].equalsIgnoreCase("-d")) { System.out.println(decrypt(args[1], args[2], args[3])); } else { System.out.println(encrypt(args[0], args[1], args[2])); } } catch (ArrayIndexOutOfBoundsException ex) { System.out.println("USAGE: java Foursquare [-d]   "); } } }

Thanks

Michael