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

Author: Hardvan

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) {

src/test/java/com/thealgorithms/bitmanipulation/NonRepeatingNumberFinderTest.java

@@ -2,22 +2,35 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
 
 /**
  * Test case for Non Repeating Number Finder
+ * This test class validates the functionality of the
+ * NonRepeatingNumberFinder by checking various scenarios.
+ *
  * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
-
 class NonRepeatingNumberFinderTest {
 
-    @Test
-    void testNonRepeatingNumberFinder() {
-        int[] arr = {1, 2, 1, 2, 6};
-        assertEquals(6, NonRepeatingNumberFinder.findNonRepeatingNumber(arr));
-        int[] arr1 = {1, 2, 1, 2};
-        assertEquals(0, NonRepeatingNumberFinder.findNonRepeatingNumber(arr1));
-        int[] arr2 = {12};
-        assertEquals(12, NonRepeatingNumberFinder.findNonRepeatingNumber(arr2));
+    @ParameterizedTest
+    @MethodSource("testCases")
+    void testNonRepeatingNumberFinder(int[] arr, int expected) {
+        assertEquals(expected, NonRepeatingNumberFinder.findNonRepeatingNumber(arr));
+    }
+
+    private static Arguments[] testCases() {
+        return new Arguments[] {
+            Arguments.of(new int[] {1, 2, 1, 2, 6}, 6), Arguments.of(new int[] {1, 2, 1, 2}, 0), // All numbers repeat
+            Arguments.of(new int[] {12}, 12), // Single non-repeating number
+            Arguments.of(new int[] {3, 5, 3, 4, 4}, 5), // More complex case
+            Arguments.of(new int[] {7, 8, 7, 9, 8, 10, 10}, 9), // Non-repeating in the middle
+            Arguments.of(new int[] {0, -1, 0, -1, 2}, 2), // Testing with negative numbers
+            Arguments.of(new int[] {Integer.MAX_VALUE, 1, 1}, Integer.MAX_VALUE), // Edge case with max int
+            Arguments.of(new int[] {2, 2, 3, 3, 4, 5, 4}, 5), // Mixed duplicates
+            Arguments.of(new int[] {}, 0) // Edge case: empty array (should be handled as per design)
+        };
     }
 }