How to Code Encryption Algorithm in Java?

Java Encryption Code HELP. HELP HELP?

• I HAVE NO idea what I am suppsoe to do for this code. All I know is, basically you have a phrase and teh computer encrypts the phrase by changuing the aphabet. ex. A=V B= Y....... and I am suppsoe to give a hint to the user like this is the letter that occurs the most in the phrase. help me

• Answer:

  OK, I have learned to use StringBuilder a lot. Deep inside the JVM, java uses StringBuilder whenever we concatenate Strings with the "+" operator. In fact, if we have 10,000 Strings, StringBuilder is x1500 percent faster than "+". Here is code that countes freqency, the highest number of like chars is the divider of a "normal" alphabet to make a new alphabet with the last chunk rotated to the front. Then, we take the original message and for each character, we find the index in the normal alphabet and use that index number to choose from the "rotated alphabet". Maybe you can do the same without StringBuilder. //>======================= import java.util.ArrayList; import java.util.Collections; import java.util.HashSet; import java.util.Set; public class AlphaShift { public static void main(String[] args) { String testData = "Resistance is futile, Captain Pichard"; String keyCrypt = countCharRepeats(testData); System.out.println("keyCrypt: " + keyCrypt); String secretMess = construeCrypt( keyCrypt, testData ); System.out.println( "secretMessage: " + secretMess); } private static String construeCrypt( String key, String mess ) { StringBuilder sb = new StringBuilder(); char alpha = ' '; // space char or 32 char omega = '~'; for (int i = (int)alpha; i <= (int)omega; i++) { sb.append( (char) i ); } System.out.println("sb: " + sb.toString()); String keyShift = key.substring(0,1); int shiftFactor = sb.indexOf(keyShift); String firstChunk = sb.substring(shiftFactor); System.out.println("firstChunk: " + firstChunk); StringBuilder sb2 = new StringBuilder( sb.substring( shiftFactor)); sb2.append( sb.substring( 0,shiftFactor)); System.out.println("sb2: " + sb2.toString()); String hint = "/" + key + "/"; // checkSum in zip files StringBuilder secretMessage = new StringBuilder(hint); for (int i = 0; i < mess.length(); i++) { String search = String.valueOf( mess.charAt(i) ); int charIndex = sb.indexOf(search); secretMessage.append( sb2.charAt(charIndex)); } return secretMessage.toString(); } static private String countCharRepeats(String msg) { String[] holder; // split das String into chars char[] chars = msg.toCharArray(); // kinda like an egg carton, only one can go into // one slot Set<Character> dupes = new HashSet<Character>(); for (char c : chars) { if (!dupes.add(c)) { continue; } } // fetch the contents of Set to a List, to sort int counter = 0; ArrayList<Character> list = new ArrayList<Character>(); for (Character character : dupes) { if( Character.isLetter(character) ) list.add(character); } // put the turkey into lexiconagle order Collections.sort(list); // now get ready to report results holder = new String[list.size()]; for (Character character : list) { int count = 0; holder[counter] = String.valueOf(character); for (int i = 0; i < chars.length; i++) { count += (character.compareTo(chars[i]) == 0) ? 1 : 0; } holder[counter] += "," + count; counter++; } int hi_ndex = 0; for (int i = 0; i < holder.length; i++) { String[] flds = holder[i].split(","); System.out.printf("%s\'s: %s%n", flds[0], flds[1]); int comp = Integer.parseInt(flds[1]); hi_ndex = (comp > hi_ndex) ? i : hi_ndex; } System.out.println("The dupes: " + list.toString()); System.out.println("The String: " + msg); return holder[ hi_ndex ]; } }