Refactor (#3923)

* NatsClient refactor

* Use lambda

spring-boot/src/main/java/com/baeldung/shutdown/Application.java

@@ -34,12 +34,9 @@ public class Application {
 
         ConfigurableApplicationContext ctx = new SpringApplicationBuilder(Application.class).web(false).run();
 
-        int exitCode = SpringApplication.exit(ctx, new ExitCodeGenerator() {
-            @Override
-            public int getExitCode() {
-                // return the error code
-                return 0;
-            }
+        int exitCode = SpringApplication.exit(ctx, () -> {
+            // return the error code
+            return 0;
         });
 
         System.out.println("Exit Spring Boot");

spring-boot/src/main/java/org/baeldung/common/resources/ExecutorServiceExitCodeGenerator.java

@@ -1,10 +1,10 @@
 package org.baeldung.common.resources;
 
+import org.springframework.boot.ExitCodeGenerator;
+
 import java.util.Objects;
 import java.util.concurrent.ExecutorService;
 
-import org.springframework.boot.ExitCodeGenerator;
-
 public class ExecutorServiceExitCodeGenerator implements ExitCodeGenerator {
 
     private ExecutorService executorService;
@@ -14,16 +14,15 @@ public class ExecutorServiceExitCodeGenerator implements ExitCodeGenerator {
 
     @Override
     public int getExitCode() {
-        int returnCode = 0;
         try {
             if (!Objects.isNull(executorService)) {
                 executorService.shutdownNow();
-                returnCode = 1;
+                return 1;
             }
-        } catch (SecurityException ex) {
-            returnCode = 0;
-        }
-        return returnCode;
-    }
 
+            return 0;
+        } catch (SecurityException ex) {
+            return 0;
+        }
+    }
 }