Adjust checkstyle rules. Make checkstyle fail the build when violations are found. Correct all current checkstyle violations.

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

@@ -28,7 +28,7 @@ public class App {
     ExecutorService executorService = Executors.newFixedThreadPool(3);
     for (int i = 0; i < 3; i++) {
       executorService.execute(() -> {
-        while (inventory.addItem(new Item()));
+        while (inventory.addItem(new Item())) {};
       });
     }
 

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

@@ -17,12 +17,18 @@ public class Inventory {
   private final List<Item> items;
   private final Lock lock;
 
+  /**
+   * Constructor
+   */
   public Inventory(int inventorySize) {
     this.inventorySize = inventorySize;
     this.items = new ArrayList<>(inventorySize);
     this.lock = new ReentrantLock();
   }
 
+  /**
+   * Add item
+   */
   public boolean addItem(Item item) {
     if (items.size() < inventorySize) {
       lock.lock();

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

@@ -77,8 +77,8 @@ public class InventoryTest {
     final ExecutorService executorService = Executors.newFixedThreadPool(THREAD_COUNT);
     for (int i = 0; i < THREAD_COUNT; i++) {
       executorService.execute(() -> {
-        while (inventory.addItem(new Item())) ;
-      });
+          while (inventory.addItem(new Item())) {};
+        });
     }
 
     // Wait until all threads have finished