fix: HideUtilityClassConstructor

Signed-off-by: JeevaRamanathan <jeevaramanathan.m@infosys.com>

Author: JeevaRamanathan

src/main/java/com/thealgorithms/strings/Isogram.java

@@ -26,6 +26,13 @@
  * Reference from https://en.wikipedia.org/wiki/Heterogram_(literature)#Isograms
  */
 public class Isogram {
+    
+    /**
+     * Private constructor to prevent instantiation of utility class.
+     */
+    private Isogram() {
+    }
+
     /**
      * Checks if a string is an isogram using boolean array approach.
      *