📍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>

dirty-flag/src/main/java/com/iluwatar/dirtyflag/App.java

@@ -25,8 +25,7 @@ package com.iluwatar.dirtyflag;
 
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * This application demonstrates the <b>Dirty Flag</b> pattern. The dirty flag behavioral pattern
@@ -51,10 +50,9 @@ import org.slf4j.LoggerFactory;
  * re-fetches from <i>world.txt</i> when needed. {@link World} mainly serves the data to the
  * front-end.
  */
+@Slf4j
 public class App {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
-
   /**
    * Program execution point.
    */

dirty-flag/src/main/java/com/iluwatar/dirtyflag/DataFetcher.java

@@ -29,18 +29,16 @@ import java.io.FileReader;
 import java.io.IOException;
 import java.util.List;
 import java.util.stream.Collectors;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
+import lombok.extern.slf4j.Slf4j;
 
 /**
  * A mock database manager -- Fetches data from a raw file.
  *
  * @author swaisuan
  */
+@Slf4j
 public class DataFetcher {
 
-  private static final Logger LOGGER = LoggerFactory.getLogger(DataFetcher.class);
-
   private final String filename = "world.txt";
   private long lastFetched;
 

dirty-flag/src/main/java/com/iluwatar/dirtyflag/World.java

@@ -37,7 +37,7 @@ public class World {
   private final DataFetcher df;
 
   public World() {
-    this.countries = new ArrayList<String>();
+    this.countries = new ArrayList<>();
     this.df = new DataFetcher();
   }