Enhance docs, add tests in SortedLinkedList (#6014)

Author: Hardvan

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

@@ -4,24 +4,42 @@
 import java.util.List;
 
 /**
- * A SortedLinkedList is a data structure that maintains a sorted list of elements.
- * Elements are ordered based on their natural ordering or by a Comparator provided at the time of creation.
- * This implementation uses a singly linked list to store the elements.
- * Further details can be found on this link
+ * The SortedLinkedList class represents a singly linked list that maintains its elements in sorted order.
+ * Elements are ordered based on their natural ordering, with smaller elements at the head and larger elements toward the tail.
+ * The class provides methods for inserting, deleting, and searching elements, as well as checking if the list is empty.
+ * <p>
+ * This implementation utilizes a singly linked list to maintain a dynamically sorted list.
+ * </p>
+ * <p>
+ * Further information can be found here:
  * https://runestone.academy/ns/books/published/cppds/LinearLinked/ImplementinganOrderedList.html
+ * </p>
+ *
+ * <b>Usage Example:</b>
+ * <pre>
+ *     SortedLinkedList list = new SortedLinkedList();
+ *     list.insert(10);
+ *     list.insert(5);
+ *     list.insert(20);
+ *     System.out.println(list); // Outputs: [5, 10, 20]
+ * </pre>
  */
 public class SortedLinkedList {
     private Node head;
     private Node tail;
 
+    /**
+     * Initializes an empty sorted linked list.
+     */
     public SortedLinkedList() {
         this.head = null;
         this.tail = null;
     }
 
     /**
-     * Inserts a new element into the sorted linked list.
-     * @param value the value to be inserted
+     * Inserts a new integer into the list, maintaining sorted order.
+     *
+     * @param value the integer to insert
      */
     public void insert(int value) {
         Node newNode = new Node(value);
@@ -48,16 +66,10 @@ public void insert(int value) {
     }
 
     /**
-     * Displays the elements of the sorted linked list.
-     */
-    public void display() {
-        System.out.println(this.toString());
-    }
-
-    /**
-     * Deletes the first occurrence of the specified element in the sorted linked list.
-     * @param value the value to be deleted
-     * @return true if the element is found and deleted, false otherwise
+     * Deletes the first occurrence of a specified integer in the list.
+     *
+     * @param value the integer to delete
+     * @return {@code true} if the element was found and deleted; {@code false} otherwise
      */
     public boolean delete(int value) {
         if (this.head == null) {
@@ -87,9 +99,10 @@ public boolean delete(int value) {
     }
 
     /**
-     * Searches for the specified element in the sorted linked list.
-     * @param value the value to be searched
-     * @return true if the element is found, false otherwise
+     * Searches for a specified integer in the list.
+     *
+     * @param value the integer to search for
+     * @return {@code true} if the value is present in the list; {@code false} otherwise
      */
     public boolean search(int value) {
         Node temp = this.head;
@@ -103,14 +116,17 @@ public boolean search(int value) {
     }
 
     /**
-     * Checks if the sorted linked list is empty.
-     * @return true if the list is empty, false otherwise
+     * Checks if the list is empty.
+     *
+     * @return {@code true} if the list is empty; {@code false} otherwise
      */
     public boolean isEmpty() {
         return head == null;
     }
+
     /**
-     * Returns a string representation of the sorted linked list.
+     * Returns a string representation of the sorted linked list in the format [element1, element2, ...].
+     *
      * @return a string representation of the sorted linked list
      */
     @Override
@@ -123,12 +139,14 @@ public String toString() {
                 temp = temp.next;
             }
             return "[" + String.join(", ", elements) + "]";
-
         } else {
             return "[]";
         }
     }
 
+    /**
+     * Node represents an element in the sorted linked list.
+     */
     public final class Node {
         public final int value;
         public Node next;

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

@@ -4,62 +4,126 @@
 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 SortedLinkedListTest {
 
+    private SortedLinkedList list;
+
+    @BeforeEach
+    public void setUp() {
+        list = new SortedLinkedList();
+    }
+
+    @Test
+    public void testInsertIntoEmptyList() {
+        list.insert(5);
+        assertEquals("[5]", list.toString());
+    }
+
     @Test
-    public void testInsert() {
-        SortedLinkedList list = new SortedLinkedList();
+    public void testInsertInSortedOrder() {
         list.insert(5);
         list.insert(3);
         list.insert(7);
         assertEquals("[3, 5, 7]", list.toString());
     }
 
     @Test
-    public void testDelete() {
-        SortedLinkedList list = new SortedLinkedList();
+    public void testInsertDuplicateValues() {
         list.insert(5);
+        list.insert(5);
+        list.insert(5);
+        assertEquals("[5, 5, 5]", list.toString());
+    }
+
+    @Test
+    public void testDeleteHeadElement() {
+        list.insert(1);
+        list.insert(2);
         list.insert(3);
-        list.insert(7);
-        assertTrue(list.delete(5));
-        assertEquals("[3, 7]", list.toString());
-        assertFalse(list.delete(10));
+        assertTrue(list.delete(1));
+        assertEquals("[2, 3]", list.toString());
     }
 
     @Test
-    public void testSearch() {
-        SortedLinkedList list = new SortedLinkedList();
-        list.insert(5);
+    public void testDeleteTailElement() {
+        list.insert(1);
+        list.insert(2);
         list.insert(3);
-        list.insert(7);
-        assertTrue(list.search(5));
-        assertFalse(list.search(10));
+        assertTrue(list.delete(3));
+        assertEquals("[1, 2]", list.toString());
+    }
+
+    @Test
+    public void testDeleteMiddleElement() {
+        list.insert(1);
+        list.insert(2);
+        list.insert(3);
+        assertTrue(list.delete(2));
+        assertEquals("[1, 3]", list.toString());
+    }
+
+    @Test
+    public void testDeleteNonexistentElement() {
+        list.insert(1);
+        list.insert(2);
+        assertFalse(list.delete(3));
     }
+
     @Test
-    public void testEmptyList() {
-        SortedLinkedList list = new SortedLinkedList();
+    public void testDeleteFromSingleElementList() {
+        list.insert(5);
+        assertTrue(list.delete(5));
         assertEquals("[]", list.toString());
+    }
+
+    @Test
+    public void testDeleteFromEmptyList() {
         assertFalse(list.delete(5));
+    }
+
+    @Test
+    public void testSearchInEmptyList() {
         assertFalse(list.search(5));
     }
+
+    @Test
+    public void testSearchForExistingElement() {
+        list.insert(3);
+        list.insert(1);
+        list.insert(5);
+        assertTrue(list.search(3));
+    }
+
+    @Test
+    public void testSearchForNonexistentElement() {
+        list.insert(3);
+        list.insert(1);
+        list.insert(5);
+        assertFalse(list.search(10));
+    }
+
     @Test
     public void testIsEmptyOnEmptyList() {
-        SortedLinkedList list = new SortedLinkedList();
         assertTrue(list.isEmpty());
     }
 
     @Test
     public void testIsEmptyOnNonEmptyList() {
-        SortedLinkedList list = new SortedLinkedList();
+        list.insert(10);
+        assertFalse(list.isEmpty());
+    }
+
+    @Test
+    public void testIsEmptyAfterInsertion() {
         list.insert(10);
         assertFalse(list.isEmpty());
     }
 
     @Test
     public void testIsEmptyAfterDeletion() {
-        SortedLinkedList list = new SortedLinkedList();
         list.insert(10);
         list.delete(10);
         assertTrue(list.isEmpty());