Added Karatsuba's multiplication algorithm

Author: adesh2756

src/main/java/com/thealgorithms/divideandconquer/KaratsubaMultiplication.java

@@ -1,34 +1,33 @@
 // Karatsuba Multiplication Algorithm
 // Explanation: https://en.wikipedia.org/wiki/Karatsuba_algorithm
 
-
 import java.util.Scanner;
 
 public class KaratsubaMultiplication {
 
+    // Private constructor to prevent instantiation
+    private KaratsubaMultiplication() {
+        throw new UnsupportedOperationException("Utility class");
+    }
+
     // Karatsuba multiplication function
     public static long karatsuba(long x, long y) {
-        // Base case for recursion
         if (x < 10 || y < 10) {
             return x * y;
         }
 
-        // Calculate the size of the numbers
         int n = Math.max(Long.toString(x).length(), Long.toString(y).length());
         int m = n / 2;
 
-        // Split the digit sequences about the middle
         long high1 = x / (long) Math.pow(10, m);
         long low1 = x % (long) Math.pow(10, m);
         long high2 = y / (long) Math.pow(10, m);
         long low2 = y % (long) Math.pow(10, m);
 
-        // 3 recursive calls
         long z0 = karatsuba(low1, low2);
         long z1 = karatsuba(low1 + high1, low2 + high2);
         long z2 = karatsuba(high1, high2);
 
-        // Combine the results
         return (z2 * (long) Math.pow(10, 2 * m)) + ((z1 - z2 - z0) * (long) Math.pow(10, m)) + z0;
     }