Enhance docs, add more tests in NonRepeatingNumberFinder (#5843)

src/main/java/com/thealgorithms/bitmanipulation/NonRepeatingNumberFinder.java

@@ -1,14 +1,30 @@
 package com.thealgorithms.bitmanipulation;
 
 /**
- * Find Non Repeating Number
+ * A utility class to find the non-repeating number in an array where every other number repeats.
+ * This class contains a method to identify the single unique number using bit manipulation.
+ *
+ * The solution leverages the properties of the XOR operation, which states that:
+ * - x ^ x = 0 for any integer x (a number XORed with itself is zero)
+ * - x ^ 0 = x for any integer x (a number XORed with zero is the number itself)
+ *
+ * Using these properties, we can find the non-repeating number in linear time with constant space.
+ *
+ * Example:
+ * Given the input array [2, 3, 5, 2, 3], the output will be 5 since it does not repeat.
+ *
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
-
 public final class NonRepeatingNumberFinder {
     private NonRepeatingNumberFinder() {
     }
 
+    /**
+     * Finds the non-repeating number in the given array.
+     *
+     * @param arr an array of integers where every number except one appears twice
+     * @return the integer that appears only once in the array or 0 if the array is empty
+     */
     public static int findNonRepeatingNumber(int[] arr) {
         int result = 0;
         for (int num : arr) {