Resolve build errors & cleanup structure (#2334)

Ciphers/Vigenere.java

@@ -0,0 +1,62 @@
+package Ciphers;
+
+/**
+ * A Java implementation of Vigenere Cipher.
+ *
+ * @author straiffix
+ * @author beingmartinbmc
+ */
+public class Vigenere {
+
+  public static String encrypt(final String message, final String key) {
+
+    StringBuilder result = new StringBuilder();
+
+    for (int i = 0, j = 0; i < message.length(); i++) {
+      char c = message.charAt(i);
+      if (Character.isLetter(c)) {
+        if (Character.isUpperCase(c)) {
+          result.append((char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A'));
+
+        } else {
+          result.append((char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a'));
+        }
+      } else {
+        result.append(c);
+      }
+      j = ++j % key.length();
+    }
+    return result.toString();
+  }
+
+  public static String decrypt(final String message, final String key) {
+    StringBuilder result = new StringBuilder();
+
+    for (int i = 0, j = 0; i < message.length(); i++) {
+
+      char c = message.charAt(i);
+      if (Character.isLetter(c)) {
+        if (Character.isUpperCase(c)) {
+          result.append((char) ('Z' - (25 - (c - key.toUpperCase().charAt(j))) % 26));
+
+        } else {
+          result.append((char) ('z' - (25 - (c - key.toLowerCase().charAt(j))) % 26));
+        }
+      } else {
+        result.append(c);
+      }
+
+      j = ++j % key.length();
+    }
+    return result.toString();
+  }
+
+  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));
+  }
+}