📍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>

null-object/README.md

@@ -57,10 +57,9 @@ We have two implementations of `Node`. The normal implementation `NodeImpl` and
 empty nodes.
 
 ```java
+@Slf4j
 public class NodeImpl implements Node {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(NodeImpl.class);
-
   private final String name;
   private final Node left;
   private final Node right;