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Caesar Cipher Command Line Decrypter
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| public class CaesarCipher { | |
| public static void main(String args[]){ | |
| if (args.length == 3) | |
| { | |
| //output decrypted string | |
| System.out.println(decryptString(args[0], args[1], args[2])); | |
| } | |
| else | |
| { | |
| // show usage message | |
| System.out.println("usage: java CaesarCipher <encrypted answer> <decrypted answer> <encrypted string>"); | |
| } | |
| } // end main | |
| private static String decryptString(String encryptedAnswer, String decryptedAnswer, String encryptedString ) | |
| { | |
| char[] letters = { 'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z' }; | |
| // calculate difference between letters | |
| char enfirst = encryptedAnswer.toLowerCase().charAt(0); | |
| char defirst = decryptedAnswer.toLowerCase().charAt(0); | |
| // cast to int | |
| int e = (int) enfirst; | |
| int d = (int) defirst; | |
| // get difference between the 2 letters | |
| int diff = d - e; | |
| StringBuffer decryptedString = new StringBuffer(); | |
| // decrypt string | |
| for (int i = 0; i < encryptedString.length(); i++) | |
| { | |
| // get current char | |
| char curChar = encryptedString.charAt(i); | |
| if (curChar != ' ' && curChar != ',' && curChar != '-') | |
| { | |
| // get number of current char | |
| int curCharInt = (int) curChar; | |
| // get position of decrypted char | |
| int posOfCharInLettersArray = ((curCharInt - 97 + diff) % letters.length + letters.length) % letters.length; | |
| // get decrypted char | |
| char newChar = letters[posOfCharInLettersArray]; | |
| // build output string | |
| decryptedString.append(newChar); | |
| } | |
| else | |
| { | |
| // build output string | |
| decryptedString.append(curChar); | |
| } | |
| } | |
| return decryptedString.toString(); | |
| } // end decryptString | |
| } // end class |
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