refactor: Enhance docs, add tests in HeapElement

DIRECTORY.md

@@ -834,6 +834,7 @@
             * heaps
               * [FibonacciHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/FibonacciHeapTest.java)
               * [GenericHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/GenericHeapTest.java)
+              * [HeapElementTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/HeapElementTest.java)
               * [LeftistHeapTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/LeftistHeapTest.java)
               * [MinPriorityQueueTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/datastructures/heaps/MinPriorityQueueTest.java)
             * lists

src/main/java/com/thealgorithms/datastructures/heaps/HeapElement.java

@@ -1,14 +1,24 @@
 package com.thealgorithms.datastructures.heaps;
 
 /**
- * Class for heap elements.<br>
+ * Class representing an element in a heap.
  *
  * <p>
- * A heap element contains two attributes: a key which will be used to build the
- * tree (int or double, either primitive type or object) and any kind of
- * IMMUTABLE object the user sees fit to carry any information he/she likes. Be
- * aware that the use of a mutable object might jeopardize the integrity of this
- * information.
+ * A heap element contains two attributes: a key used for ordering in the heap
+ * (which can be of type int or double, either as primitive types or as wrapper objects)
+ * and an additional immutable object that can store any supplementary information the user desires.
+ * Note that using mutable objects may compromise the integrity of this information.
+ * </p>
+ *
+ * <p>
+ * The key attribute is used to determine the order of elements in the heap,
+ * while the additionalInfo attribute can carry user-defined data associated with the key.
+ * </p>
+ *
+ * <p>
+ * This class provides multiple constructors to accommodate various key types and includes
+ * methods to retrieve the key and additional information.
+ * </p>
  *
  * @author Nicolas Renard
  */
@@ -19,71 +29,83 @@ public class HeapElement {
 
     // Constructors
     /**
-     * @param key : a number of primitive type 'double'
-     * @param info : any kind of IMMUTABLE object. May be null, since the
-     * purpose is only to carry additional information of use for the user
+     * Creates a HeapElement with the specified key and additional information.
+     *
+     * @param key  the key of the element (primitive type double)
+     * @param info any immutable object containing additional information, may be null
      */
     public HeapElement(double key, Object info) {
         this.key = key;
         this.additionalInfo = info;
     }
 
     /**
-     * @param key : a number of primitive type 'int'
-     * @param info : any kind of IMMUTABLE object. May be null, since the
-     * purpose is only to carry additional information of use for the user
+     * Creates a HeapElement with the specified key and additional information.
+     *
+     * @param key  the key of the element (primitive type int)
+     * @param info any immutable object containing additional information, may be null
      */
     public HeapElement(int key, Object info) {
         this.key = key;
         this.additionalInfo = info;
     }
 
     /**
-     * @param key : a number of object type 'Integer'
-     * @param info : any kind of IMMUTABLE object. May be null, since the
-     * purpose is only to carry additional information of use for the user
+     * Creates a HeapElement with the specified key and additional information.
+     *
+     * @param key  the key of the element (object type Integer)
+     * @param info any immutable object containing additional information, may be null
      */
     public HeapElement(Integer key, Object info) {
         this.key = key;
         this.additionalInfo = info;
     }
 
     /**
-     * @param key : a number of object type 'Double'
-     * @param info : any kind of IMMUTABLE object. May be null, since the
-     * purpose is only to carry additional information of use for the user
+     * Creates a HeapElement with the specified key and additional information.
+     *
+     * @param key  the key of the element (object type Double)
+     * @param info any immutable object containing additional information, may be null
      */
     public HeapElement(Double key, Object info) {
         this.key = key;
         this.additionalInfo = info;
     }
 
     /**
-     * @param key : a number of primitive type 'double'
+     * Creates a HeapElement with the specified key.
+     *
+     * @param key the key of the element (primitive type double)
      */
     public HeapElement(double key) {
         this.key = key;
         this.additionalInfo = null;
     }
 
     /**
-     * @param key : a number of primitive type 'int'
+     * Creates a HeapElement with the specified key.
+     *
+     * @param key the key of the element (primitive type int)
      */
     public HeapElement(int key) {
         this.key = key;
         this.additionalInfo = null;
     }
 
     /**
-     * @param key : a number of object type 'Integer'
+     * Creates a HeapElement with the specified key.
+     *
+     * @param key the key of the element (object type Integer)
      */
     public HeapElement(Integer key) {
         this.key = key;
         this.additionalInfo = null;
     }
 
     /**
-     * @param key : a number of object type 'Double'
+     * Creates a HeapElement with the specified key.
+     *
+     * @param key the key of the element (object type Double)
      */
     public HeapElement(Double key) {
         this.key = key;
@@ -92,46 +114,57 @@ public HeapElement(Double key) {
 
     // Getters
     /**
-     * @return the object containing the additional info provided by the user.
+     * Returns the object containing the additional information provided by the user.
+     *
+     * @return the additional information
      */
     public Object getInfo() {
         return additionalInfo;
     }
 
     /**
-     * @return the key value of the element
+     * Returns the key value of the element.
+     *
+     * @return the key of the element
      */
     public double getKey() {
         return key;
     }
 
     // Overridden object methods
+    /**
+     * Returns a string representation of the heap element.
+     *
+     * @return a string describing the key and additional information
+     */
+    @Override
     public String toString() {
-        return "Key: " + key + " - " + additionalInfo.toString();
+        return "Key: " + key + " - " + (additionalInfo != null ? additionalInfo.toString() : "No additional info");
     }
 
     /**
-     * @param otherHeapElement
-     * @return true if the keys on both elements are identical and the
-     * additional info objects are identical.
+     * Compares this heap element to another object for equality.
+     *
+     * @param o the object to compare with
+     * @return true if the keys and additional information are identical, false otherwise
      */
     @Override
     public boolean equals(Object o) {
-        if (o != null) {
-            if (!(o instanceof HeapElement)) {
-                return false;
-            }
-            HeapElement otherHeapElement = (HeapElement) o;
-            return ((this.key == otherHeapElement.key) && (this.additionalInfo.equals(otherHeapElement.additionalInfo)));
+        if (o instanceof HeapElement otherHeapElement) {
+            return this.key == otherHeapElement.key && (this.additionalInfo != null ? this.additionalInfo.equals(otherHeapElement.additionalInfo) : otherHeapElement.additionalInfo == null);
         }
         return false;
     }
 
+    /**
+     * Returns a hash code value for the heap element.
+     *
+     * @return a hash code value for this heap element
+     */
     @Override
     public int hashCode() {
-        int result = 0;
-        result = 31 * result + (int) key;
-        result = 31 * result + (additionalInfo != null ? additionalInfo.hashCode() : 0);
+        int result = 31 * (int) key;
+        result += (additionalInfo != null) ? additionalInfo.hashCode() : 0;
         return result;
     }
 }

src/test/java/com/thealgorithms/datastructures/heaps/HeapElementTest.java

@@ -0,0 +1,55 @@
+package com.thealgorithms.datastructures.heaps;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+import org.junit.jupiter.api.Test;
+
+class HeapElementTest {
+
+    @Test
+    void testConstructorAndGetters() {
+        HeapElement element = new HeapElement(5.0, "Info");
+        assertEquals(5.0, element.getKey());
+        assertEquals("Info", element.getInfo());
+    }
+
+    @Test
+    void testConstructorWithNullInfo() {
+        HeapElement element = new HeapElement(10);
+        assertEquals(10, element.getKey());
+        assertNull(element.getInfo());
+    }
+
+    @Test
+    void testToString() {
+        HeapElement element = new HeapElement(7.5, "TestInfo");
+        assertEquals("Key: 7.5 - TestInfo", element.toString());
+
+        HeapElement elementWithoutInfo = new HeapElement(3);
+        assertEquals("Key: 3.0 - No additional info", elementWithoutInfo.toString());
+    }
+
+    @Test
+    void testEquals() {
+        HeapElement element1 = new HeapElement(2.5, "Data");
+        HeapElement element2 = new HeapElement(2.5, "Data");
+        HeapElement element3 = new HeapElement(3.0, "DifferentData");
+
+        assertEquals(element1, element2); // Same key and info
+        assertNotEquals(element1, element3); // Different key
+        assertNotEquals(null, element1); // Check for null
+        assertNotEquals("String", element1); // Check for different type
+    }
+
+    @Test
+    void testHashCode() {
+        HeapElement element1 = new HeapElement(4, "HashMe");
+        HeapElement element2 = new HeapElement(4, "HashMe");
+        HeapElement element3 = new HeapElement(4, "DifferentHash");
+
+        assertEquals(element1.hashCode(), element2.hashCode()); // Same key and info
+        assertNotEquals(element1.hashCode(), element3.hashCode()); // Different info
+    }
+}