refactor: Enhance docs, remove main, add tests in `SearchSinglyLink…

DIRECTORY.md

@@ -887,6 +887,7 @@
               * [QuickSortLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/QuickSortLinkedListTest.java)
               * [ReverseKGroupTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/ReverseKGroupTest.java)
               * [RotateSinglyLinkedListsTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/RotateSinglyLinkedListsTest.java)
+              * [SearchSinglyLinkedListRecursionTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SearchSinglyLinkedListRecursionTest.java)
               * [SinglyLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SinglyLinkedListTest.java)
               * [SkipListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SkipListTest.java)
               * [SortedLinkedListTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/lists/SortedLinkedListTest.java)

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

@@ -1,31 +1,45 @@
 package com.thealgorithms.datastructures.lists;
 
+/**
+ * The SearchSinglyLinkedListRecursion class extends SinglyLinkedList and provides
+ * a method to search for a value in a singly linked list using recursion.
+ * <p>
+ * This class demonstrates a recursive approach to check if a given integer value is
+ * present in the linked list. The search method calls a private recursive helper method
+ * `searchRecursion`, which checks each node's value and moves to the next node if necessary.
+ * </p>
+ * <p>
+ * Example:
+ * Given a list containing the values 1 -> 2 -> 3 -> 4, calling search(3) will return `true`,
+ * while calling search(5) will return `false`.
+ * </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(n), due to the recursive call stack in the worst case.</li>
+ * </ul>
+ * </p>
+ */
 public class SearchSinglyLinkedListRecursion extends SinglyLinkedList {
 
-    public static void main(String[] args) {
-        SearchSinglyLinkedListRecursion list = new SearchSinglyLinkedListRecursion();
-        for (int i = 1; i <= 10; ++i) {
-            list.insert(i);
-        }
-
-        for (int i = 1; i <= 10; ++i) {
-            assert list.search(i);
-        }
-        assert !list.search(-1) && !list.search(100);
-    }
-
     /**
-     * Test if the value key is present in the list using recursion.
+     * Recursively searches for a given value in the linked list.
      *
-     * @param node the head node.
-     * @param key the value to be searched.
-     * @return {@code true} if key is present in the list, otherwise
-     * {@code false}.
+     * @param node the head node to start the search.
+     * @param key the integer value to be searched for.
+     * @return {@code true} if the value `key` is present in the list; otherwise, {@code false}.
      */
     private boolean searchRecursion(Node node, int key) {
         return (node != null && (node.value == key || searchRecursion(node.next, key)));
     }
 
+    /**
+     * Public search method to determine if a key is present in the linked list.
+     *
+     * @param key the integer value to be searched for.
+     * @return {@code true} if the value `key` is present in the list; otherwise, {@code false}.
+     */
     @Override
     public boolean search(int key) {
         return searchRecursion(getHead(), key);

src/test/java/com/thealgorithms/datastructures/lists/SearchSinglyLinkedListRecursionTest.java

@@ -0,0 +1,89 @@
+package com.thealgorithms.datastructures.lists;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class SearchSinglyLinkedListRecursionTest {
+
+    private SearchSinglyLinkedListRecursion list;
+
+    @BeforeEach
+    public void setUp() {
+        list = new SearchSinglyLinkedListRecursion();
+    }
+
+    @Test
+    public void testSearchInEmptyList() {
+        // Test searching for a value in an empty list (should return false)
+        assertFalse(list.search(1));
+    }
+
+    @Test
+    public void testSearchSingleElementListFound() {
+        // Insert a single element and search for it
+        list.insert(5);
+        assertTrue(list.search(5));
+    }
+
+    @Test
+    public void testSearchSingleElementListNotFound() {
+        // Insert a single element and search for a non-existent value
+        list.insert(5);
+        assertFalse(list.search(10));
+    }
+
+    @Test
+    public void testSearchMultipleElementsListFound() {
+        // Insert multiple elements and search for a middle value
+        for (int i = 1; i <= 10; i++) {
+            list.insert(i);
+        }
+        assertTrue(list.search(5));
+    }
+
+    @Test
+    public void testSearchMultipleElementsListFirstElement() {
+        // Insert multiple elements and search for the first element
+        for (int i = 1; i <= 10; i++) {
+            list.insert(i);
+        }
+        assertTrue(list.search(1));
+    }
+
+    @Test
+    public void testSearchMultipleElementsListLastElement() {
+        // Insert multiple elements and search for the last element
+        for (int i = 1; i <= 10; i++) {
+            list.insert(i);
+        }
+        assertTrue(list.search(10));
+    }
+
+    @Test
+    public void testSearchMultipleElementsListNotFound() {
+        // Insert multiple elements and search for a non-existent element
+        for (int i = 1; i <= 10; i++) {
+            list.insert(i);
+        }
+        assertFalse(list.search(15));
+    }
+
+    @Test
+    public void testSearchNegativeValues() {
+        // Insert positive and negative values and search for a negative value
+        list.insert(-5);
+        list.insert(-10);
+        list.insert(5);
+        assertTrue(list.search(-10));
+        assertFalse(list.search(-3));
+    }
+
+    @Test
+    public void testSearchZeroValue() {
+        list.insert(0);
+        assertTrue(list.search(0));
+    }
+}