[JAVA-13962] Align code with article + clean up (#13012)

* [JAVA-13962] Align code with article + clean up

* [JAVA-13962] Clean up

Co-authored-by: panagiotiskakos <panagiotis.kakos@libra-is.com>

core-java-modules/core-java-concurrency-basic/src/main/java/com/baeldung/concurrent/executorservice/DelayedCallable.java

@@ -1,5 +1,6 @@
 package com.baeldung.concurrent.executorservice;
 
+
 import java.util.concurrent.Callable;
 import java.util.concurrent.CountDownLatch;
 

core-java-modules/core-java-concurrency-basic/src/test/java/com/baeldung/concurrent/executorservice/WaitingForThreadsToFinishManualTest.java

@@ -1,15 +1,24 @@
 package com.baeldung.concurrent.executorservice;
 
+import static junit.framework.TestCase.assertTrue;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CompletionService;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorCompletionService;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.TimeUnit;
+
 import org.junit.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.Arrays;
-import java.util.List;
-import java.util.concurrent.*;
-
-import static junit.framework.TestCase.assertTrue;
-
 public class WaitingForThreadsToFinishManualTest {
 
     private static final Logger LOG = LoggerFactory.getLogger(WaitingForThreadsToFinishManualTest.class);

core-java-modules/core-java-concurrency-simple/src/main/java/com/baeldung/concurrent/executorservice/CallableTask.java

@@ -0,0 +1,10 @@
+package com.baeldung.concurrent.executorservice;
+
+import java.util.concurrent.Callable;
+
+public class CallableTask implements Callable<String> {
+    @Override
+    public String call() throws Exception {
+        return "Hello world";
+    }
+}

core-java-modules/core-java-concurrency-simple/src/main/java/com/baeldung/concurrent/executorservice/ExecutorServiceDemo.java

@@ -1,27 +0,0 @@
-package com.baeldung.concurrent.executorservice;
-
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
-public class ExecutorServiceDemo {
-
-    ExecutorService executor = Executors.newFixedThreadPool(10);
-
-    public void execute() {
-
-        executor.submit(() -> {
-            new Task();
-        });
-
-        executor.shutdown();
-        executor.shutdownNow();
-        try {
-            executor.awaitTermination(20l, TimeUnit.NANOSECONDS);
-        } catch (InterruptedException e) {
-            e.printStackTrace();
-        }
-
-    }
-
-}

core-java-modules/core-java-concurrency-simple/src/main/java/com/baeldung/concurrent/executorservice/ScheduledExecutorServiceDemo.java

@@ -1,13 +1,15 @@
-package com.baeldung.concurrent.Scheduledexecutorservice;
+package com.baeldung.concurrent.executorservice;
 
 import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
 import java.util.concurrent.ScheduledExecutorService;
-import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
 
 public class ScheduledExecutorServiceDemo {
 
+	private Task runnableTask;
+	private CallableTask callableTask;
 	private void execute() {
 		ScheduledExecutorService executorService = Executors.newSingleThreadScheduledExecutor();
 		getTasksToRun().apply(executorService);
@@ -21,23 +23,14 @@ public class ScheduledExecutorServiceDemo {
 	}
 
 	private Function<ScheduledExecutorService, Void> getTasksToRun() {
+
+		runnableTask = new Task();
+		callableTask = new CallableTask();
+
 		return (executorService -> {
-			ScheduledFuture<?> scheduledFuture1 = executorService.schedule(() -> {
-				// Task
-			}, 1, TimeUnit.SECONDS);
-
-			ScheduledFuture<?> scheduledFuture2 = executorService.scheduleAtFixedRate(() -> {
-				// Task
-			}, 1, 10, TimeUnit.SECONDS);
-
-			ScheduledFuture<?> scheduledFuture3 = executorService.scheduleWithFixedDelay(() -> {
-				// Task
-			}, 1, 10, TimeUnit.SECONDS);
-
-			ScheduledFuture<String> scheduledFuture4 = executorService.schedule(() -> {
-				// Task
-				return "Hellow world";
-			}, 1, TimeUnit.SECONDS);
+			Future<String> resultFuture = executorService.schedule(callableTask, 1, TimeUnit.SECONDS);
+			executorService.scheduleAtFixedRate( runnableTask, 100, 450, TimeUnit.SECONDS);
+			executorService.scheduleWithFixedDelay( runnableTask, 100, 150, TimeUnit.SECONDS);
 			return null;
 		});
 	}
@@ -48,5 +41,4 @@ public class ScheduledExecutorServiceDemo {
 		demo.executeWithMultiThread();
 	}
 
-
 }