Daily Question [03-11]

Consider the following implementation to support Edgar Allan Poe's Goldbug story. The original encrypted text is found below

53++!305))6*;4826)4+.)4+);806*;48!8`60))85;;]8*;:+*8!83(88)5*!;46(;88*96*?;8)*+(;485);5*!2:*+(;4956*2(5*-4)8`8*;4069285);)6!8)4++;1(+9;48081;8:8+1;48!85;4)485!528806*81(+9;48;(88;4(+?34;48)4+;161;:188;+?;

The following program can retrieve such fragments from disk and provide an interactive experience in decoding such ciphers. You can also find this sample code from the Goldbug project which is available from the CVS repository on the class SourceForge project page.

package original;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Hashtable;
import java.util.Iterator;
import java.util.Scanner;

/**
 * 1. But, there being no division, my first step was to ascertain the predominant
 *  letters, as well as the least frequent. Counting all, I constructed a table, 
 *  thus:
 * 
 * @author George Heineman
 *
 */
public class Goldbug {
	/** Read input. */
	static Scanner sc;
	
	/** The code. */
	static String code;
	
	/** Unknown character. */
	public static char unknown = '\001';
	
	/** Coded characters and their replacement. */
	static Hashtable<Character,Character> key = new Hashtable<Character,Character>(); 
	
	/** Characters in decreasing frequency. */
	static char chars[];
	
	/** And their frequency. */
	static int freq[];

	/** Compute frequency and build key table. */
	private static void process() {
		for (int i = 0; i < code.length(); i++) {
			char ch = code.charAt(i);
			if (key.containsKey(ch)) continue;
			
			key.put(ch, unknown);
		}
		
		int numUnique = key.size();
		chars = new char[numUnique];
		freq = new int [numUnique];
		
		int idx = 0;
		for (Iterator<Character> it = key.keySet().iterator(); it.hasNext(); idx++) {
			char ch = it.next();
			chars[idx] = ch;
			for (int i = 0 ; i < code.length(); i++) {
				if (code.charAt(i) == ch) {
					freq[idx]++;
				}
			}
		}
		
		// now sort by frequency. Bubble sort, for goodness' sake!
		for (int i = 0; i < freq.length - 1; i++) {
			for (int j = i+1; j < freq.length; j++) {
				if (freq[i] < freq[j]) {
					int tmp = freq[i];
					freq[i] = freq[j];
					freq[j] = tmp;
					
					char tc = chars[i];
					chars[i] = chars[j];
					chars[j] = tc;
				}
			}
		}
	}
	
	public static String decoded () {
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < code.length(); i++) {
			sb.append(key.get(code.charAt(i)));
		}
		
		return sb.toString();
	}
	
	/** Output current key. */
	public static String showKey() {
		StringBuilder sb = new StringBuilder();
		for (Iterator<Character> it = key.keySet().iterator(); it.hasNext(); ) {
			char ch = it.next();
			char dec = key.get(ch);
			if (dec != unknown) {
				sb.append (" ").append(ch).append("=").append(dec).append(" ");
			}
		}
		
		return sb.toString();
	}
	
	/** Launch whole program. */
	public static void main (String []args) throws FileNotFoundException {
		sc = new Scanner (System.in);
		System.out.println ("What file contains the coded text?");
		String fileName = sc.nextLine();
		
		File f = new File (fileName);
		if (!f.exists()) {
			System.out.println (f + " does not exist.");
			System.exit(0);
		}
		
		Scanner fscan = new Scanner (f);
		StringBuilder sb = new StringBuilder();
		while (fscan.hasNext()) {
			sb.append(fscan.nextLine());
		}
		fscan.close();
		
		System.out.println ("Welcome to the GoldBug decoding system");
		System.out.println ("Version 1.0");
		
		code = sb.toString();
		process();
		
		String s;
		while (true) {
			System.out.println ("\nCode is:");
			System.out.println (code);
			System.out.println (decoded());
			System.out.println ("\nCurrent coded letters:");
			System.out.println (showKey());
			
			System.out.println ("\nOptions:");
			System.out.println (" [f] Show letter frequency");
			System.out.println (" [a] Assign a letter");
			System.out.println (" [c] Clear a letter assignment");
			System.out.println (" [q] Quit!");
			System.out.println ();
			
			try {
				while (true) {
					s = sc.nextLine();
					if (s.equals("q")) { System.exit(0); }
					if (s.equals("f")) {
						for (int i = 0; i < chars.length; i++) {
							System.out.print (chars[i]);
							System.out.print (" ");
						}
						break;
					} else if (s.equals ("c")) {
						System.out.println ("Enter the coded letter you wish to clear");
						s = sc.nextLine();
						key.put(s.charAt(0), unknown);
						break;
					} else if (s.equals ("a")) {
						System.out.println ("Enter the coded letter you wish to assign");
						s = sc.nextLine();
						char c1 = s.charAt(0);
						System.out.println ("What code should be given?");
						s = sc.nextLine();
						char c2 = s.charAt(0);
						key.put(c1,	c2);
						break;
					}
					
					System.out.println ("\n Enter one of [facq] please");
				}
			} catch (Exception e) {
				e.printStackTrace();
				System.err.println ("\nAn error occured. Try again!");
			}
		}
	}
}

Your challenge? Write a graphical version of this program; use either Java AWT or Java SWING. I will post my solution on Wednesday March 12th at 9:00 PM. If you complete a working version and want to show it to me (and allow me to make it available to others in the class as well) email it to me by that time.

The purpose of the exercise is to get you to think about the artifacts that we design and their ability (and inability) to be used in different contexts. How much, for example, of this initial code will likely be usable in the graphic version that you develop?