Enhance docs, add tests in RotateSinglyLinkedLists (#6011)

src/main/java/com/thealgorithms/datastructures/lists/RotateSinglyLinkedLists.java

@@ -1,11 +1,43 @@
 package com.thealgorithms.datastructures.lists;
 
 /**
- * Rotate a list
- * @author Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
+ * The RotateSinglyLinkedLists class provides a method to rotate a singly linked list
+ * to the right by a specified number of positions.
+ * <p>
+ * In a right rotation by `k` steps, each node in the list moves `k` positions to the right.
+ * Nodes that are rotated off the end of the list are placed back at the beginning.
+ * </p>
+ * <p>
+ * Example:
+ * Given linked list: 1 -> 2 -> 3 -> 4 -> 5 and k = 2, the output will be:
+ * 4 -> 5 -> 1 -> 2 -> 3.
+ * </p>
+ * <p>
+ * Edge Cases:
+ * <ul>
+ *   <li>If the list is empty, returns null.</li>
+ *   <li>If `k` is 0 or a multiple of the list length, the list remains unchanged.</li>
+ * </ul>
+ * </p>
+ * <p>
+ * Complexity:
+ * <ul>
+ *   <li>Time Complexity: O(n), where n is the number of nodes in the linked list.</li>
+ *   <li>Space Complexity: O(1), as we only use a constant amount of additional space.</li>
+ * </ul>
+ * </p>
+ *
+ * Author: Bama Charan Chhandogi (https://github.com/BamaCharanChhandogi)
  */
-
 public class RotateSinglyLinkedLists {
+
+    /**
+     * Rotates a singly linked list to the right by `k` positions.
+     *
+     * @param head The head node of the singly linked list.
+     * @param k The number of positions to rotate the list to the right.
+     * @return The head of the rotated linked list.
+     */
     public Node rotateRight(Node head, int k) {
         if (head == null || head.next == null || k == 0) {
             return head;