📍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/main/java/com/iluwatar/doublechecked/locking/App.java

@@ -26,8 +26,7 @@ package com.iluwatar.doublechecked.locking;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.IntStream;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * Double Checked Locking is a concurrency design pattern used to reduce the overhead of acquiring a
@@ -40,10 +39,9 @@ import org.slf4j.LoggerFactory;
  * locking to add item to inventory. In this method, the thread which gets the lock first adds the
  * item.
  */
+@Slf4j
 public class App {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-
   /**
    * Program entry point.
    *
@@ -63,6 +61,7 @@ public class App {
       executorService.awaitTermination(5, TimeUnit.SECONDS);
     } catch (InterruptedException e) {
       LOGGER.error("Error waiting for ExecutorService shutdown");
+      Thread.currentThread().interrupt();
     }
   }
 }

double-checked-locking/src/main/java/com/iluwatar/doublechecked/locking/Inventory.java

@@ -27,16 +27,14 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReentrantLock;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * Inventory.
  */
+@Slf4j
 public class Inventory {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(Inventory.class);
-
   private final int inventorySize;
   private final List<Item> items;
   private final Lock lock;

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);