General performance improvement (#6078)

src/main/java/com/thealgorithms/ciphers/AES.java

@@ -2418,8 +2418,6 @@ public final class AES {
             rBytes = new StringBuilder(rBytes.substring(0, i * 2) + currentByteBits + rBytes.substring((i + 1) * 2));
         }
 
-        // t = new BigInteger(rBytes, 16);
-        // return t;
         return new BigInteger(rBytes.toString(), 16);
     }
 

src/main/java/com/thealgorithms/ciphers/AffineCipher.java

@@ -34,19 +34,19 @@ final class AffineCipher {
      */
     static String encryptMessage(char[] msg) {
         // Cipher Text initially empty
-        String cipher = "";
+        StringBuilder cipher = new StringBuilder();
         for (int i = 0; i < msg.length; i++) {
             // Avoid space to be encrypted
             /* applying encryption formula ( a * x + b ) mod m
             {here x is msg[i] and m is 26} and added 'A' to
             bring it in the range of ASCII alphabet [65-90 | A-Z] */
             if (msg[i] != ' ') {
-                cipher += (char) ((((a * (msg[i] - 'A')) + b) % 26) + 'A');
+                cipher.append((char) ((((a * (msg[i] - 'A')) + b) % 26) + 'A'));
             } else { // else simply append space character
-                cipher += msg[i];
+                cipher.append(msg[i]);
             }
         }
-        return cipher;
+        return cipher.toString();
     }
 
     /**
@@ -56,7 +56,7 @@ final class AffineCipher {
      * @return the decrypted plaintext message
      */
     static String decryptCipher(String cipher) {
-        String msg = "";
+        StringBuilder msg = new StringBuilder();
         int aInv = 0;
         int flag;
 
@@ -75,13 +75,13 @@ final class AffineCipher {
             {here x is cipher[i] and m is 26} and added 'A'
             to bring it in the range of ASCII alphabet [65-90 | A-Z] */
             if (cipher.charAt(i) != ' ') {
-                msg += (char) (((aInv * ((cipher.charAt(i) - 'A') - b + 26)) % 26) + 'A');
+                msg.append((char) (((aInv * ((cipher.charAt(i) - 'A') - b + 26)) % 26) + 'A'));
             } else { // else simply append space character
-                msg += cipher.charAt(i);
+                msg.append(cipher.charAt(i));
             }
         }
 
-        return msg;
+        return msg.toString();
     }
 
     // Driver code

src/main/java/com/thealgorithms/ciphers/Blowfish.java

@@ -1078,7 +1078,7 @@ public class Blowfish {
      * @return String object which is a binary representation of the hex number passed as parameter
      */
     private String hexToBin(String hex) {
-        String binary = "";
+        StringBuilder binary = new StringBuilder();
         long num;
         String binary4B;
         int n = hex.length();
@@ -1089,9 +1089,9 @@ public class Blowfish {
             binary4B = "0000" + binary4B;
 
             binary4B = binary4B.substring(binary4B.length() - 4);
-            binary += binary4B;
+            binary.append(binary4B);
         }
-        return binary;
+        return binary.toString();
     }
 
     /**
@@ -1103,12 +1103,12 @@ public class Blowfish {
      */
     private String binToHex(String binary) {
         long num = Long.parseUnsignedLong(binary, 2);
-        String hex = Long.toHexString(num);
+        StringBuilder hex = new StringBuilder(Long.toHexString(num));
         while (hex.length() < (binary.length() / 4)) {
-            hex = "0" + hex;
+            hex.insert(0, "0");
         }
 
-        return hex;
+        return hex.toString();
     }
 
     /**
@@ -1121,12 +1121,12 @@ public class Blowfish {
     private String xor(String a, String b) {
         a = hexToBin(a);
         b = hexToBin(b);
-        String ans = "";
+        StringBuilder ans = new StringBuilder();
         for (int i = 0; i < a.length(); i++) {
-            ans += (char) (((a.charAt(i) - '0') ^ (b.charAt(i) - '0')) + '0');
+            ans.append((char) (((a.charAt(i) - '0') ^ (b.charAt(i) - '0')) + '0'));
         }
-        ans = binToHex(ans);
-        return ans;
+        ans = new StringBuilder(binToHex(ans.toString()));
+        return ans.toString();
     }
 
     /**