📍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>

monad/src/main/java/com/iluwatar/monad/App.java

@@ -26,8 +26,7 @@ package com.iluwatar.monad;
 import java.util.Objects;
 import java.util.function.Function;
 import java.util.function.Predicate;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * The Monad pattern defines a monad structure, that enables chaining operations in pipelines and
@@ -44,10 +43,9 @@ import org.slf4j.LoggerFactory;
  * <p>As a validation result {@link Validator#get()} either returns valid object
  * or throws {@link IllegalStateException} with list of exceptions collected during validation.
  */
+@Slf4j
 public class App {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-
   /**
    * Program entry point.
    *

monad/src/test/java/com/iluwatar/monad/AppTest.java

@@ -31,7 +31,7 @@ import org.junit.jupiter.api.Test;
 public class AppTest {
 
   @Test
-  public void testMain() {
+  void testMain() {
     App.main(new String[]{});
   }
 

monad/src/test/java/com/iluwatar/monad/MonadTest.java

@@ -35,7 +35,7 @@ import org.junit.jupiter.api.Test;
 public class MonadTest {
 
   @Test
-  public void testForInvalidName() {
+  void testForInvalidName() {
     var tom = new User(null, 21, Sex.MALE, "tom@foo.bar");
     assertThrows(
         IllegalStateException.class,
@@ -46,7 +46,7 @@ public class MonadTest {
   }
 
   @Test
-  public void testForInvalidAge() {
+  void testForInvalidAge() {
     var john = new User("John", 17, Sex.MALE, "john@qwe.bar");
     assertThrows(
         IllegalStateException.class,
@@ -58,7 +58,7 @@ public class MonadTest {
   }
 
   @Test
-  public void testForValid() {
+  void testForValid() {
     var sarah = new User("Sarah", 42, Sex.FEMALE, "sarah@det.org");
     var validated = Validator.of(sarah)
         .validate(User::getName, Objects::nonNull, "name cannot be null")