📍Use lombok, reformat, and optimize the code (#1560)

* Use lombok, reformat, and optimize the code

* Fix merge conflicts and some sonar issues

Co-authored-by: va1m <va1m@email.com>

double-checked-locking/src/test/java/com/iluwatar/doublechecked/locking/InventoryTest.java

@@ -47,17 +47,17 @@ import org.slf4j.LoggerFactory;
  *
  * @author Jeroen Meulemeester
  */
-public class InventoryTest {
+class InventoryTest {
 
   private InMemoryAppender appender;
 
   @BeforeEach
-  public void setUp() {
+  void setUp() {
     appender = new InMemoryAppender(Inventory.class);
   }
 
   @AfterEach
-  public void tearDown() {
+  void tearDown() {
     appender.stop();
   }
 
@@ -79,7 +79,7 @@ public class InventoryTest {
    * item limit.
    */
   @Test
-  public void testAddItem() throws Exception {
+  void testAddItem() throws Exception {
     assertTimeout(ofMillis(10000), () -> {
       // Create a new inventory with a limit of 1000 items and put some load on the add method
       final var inventory = new Inventory(INVENTORY_SIZE);