Merge pull request #418 from straiffix/Vigenere-add

Vigenere add

ciphers/Vigenere.java

@@ -0,0 +1,67 @@
+package ciphers;
+
+/**
+ * A Java implementation of Vigenere Cipher.
+ * @author  straiffix
+ */
+
+
+public class Vigenere  {
+
+     public static String encrypt(final String message, final String key)
+    {
+
+        String result = "";
+
+        for (int i = 0, j = 0; i < message.length(); i++) {
+            char c = message.charAt(i);
+            if (Character.isLetter(c)){
+                if(Character.isUpperCase(c)) {
+                    result += (char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A');
+
+                } else {
+                    result += (char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a');
+
+                }
+            } else {
+                result+=c;
+            }
+            j = ++j % key.length();
+        }
+        return result;
+    }
+
+     public static String decrypt( final String message, final String key)
+    {
+        String result ="";
+
+        for(int i = 0, j = 0; i < message.length(); i++){
+
+            char c = message.charAt(i);
+            if (Character.isLetter(c)){
+                if(Character.isUpperCase(c)) {
+                    result += ((char)('Z'-(25-(c-key.toUpperCase().charAt(j)))%26));
+
+                } else {
+                    result += ((char)('z'-(25-(c-key.toLowerCase().charAt(j)))%26));
+
+                }
+            } else {
+                result+=c;
+            }
+
+            j = ++j % key.length();
+
+        }
+        return result;
+     }
+    public static void main (String [] args){
+        String text="Hello World!";
+        String key="itsakey";
+        System.out.println(text);
+        String ciphertext=encrypt(text, key);
+        System.out.println(ciphertext);
+        System.out.println(decrypt(ciphertext, key));
+
+    }
+}