Replaced String with StringBuilder so multiple String Objects don't get created (#2238)

ciphers/Vigenere.java

@@ -4,50 +4,51 @@ 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) {
 
-    String result = "";
+    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 += (char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A');
+          result.append((char) ((c + key.toUpperCase().charAt(j) - 2 * 'A') % 26 + 'A'));
 
         } else {
-          result += (char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a');
+          result.append((char) ((c + key.toLowerCase().charAt(j) - 2 * 'a') % 26 + 'a'));
         }
       } else {
-        result += c;
+        result.append(c);
       }
       j = ++j % key.length();
     }
-    return result;
+    return result.toString();
   }
 
   public static String decrypt(final String message, final String key) {
-    String result = "";
+    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 += ((char) ('Z' - (25 - (c - key.toUpperCase().charAt(j))) % 26));
+          result.append((char) ('Z' - (25 - (c - key.toUpperCase().charAt(j))) % 26));
 
         } else {
-          result += ((char) ('z' - (25 - (c - key.toLowerCase().charAt(j))) % 26));
+          result.append((char) ('z' - (25 - (c - key.toLowerCase().charAt(j))) % 26));
         }
       } else {
-        result += c;
+        result.append(c);
       }
 
       j = ++j % key.length();
     }
-    return result;
+    return result.toString();
   }
 
   public static void main(String[] args) {