code for thread creation (#12971)

* code for thread creation

* code refactored

* added code for executor service thread pools

* moved the files to a single module

Co-authored-by: Vartika_Nigam <Vartika_Nigam@DellTeam.com>

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/CustomThread.java

@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.threads.create;
+
+public class CustomThread extends Thread{
+
+    @Override
+    public void run(){
+        System.out.println(Thread.currentThread().getName()+" started");
+    }
+
+    public static void main(String[] args){
+        CustomThread t1 = new CustomThread();
+        t1.start();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/TestClass.java

@@ -0,0 +1,15 @@
+package com.baeldung.concurrent.threads.create;
+
+public class TestClass implements Runnable{
+
+    @Override
+    public void run(){
+        System.out.println(Thread.currentThread().getName()+" started");
+    }
+
+    public static void main(String[] args){
+        TestClass testClassRef = new TestClass();
+        Thread t1 = new Thread(testClassRef);
+        t1.start();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/threadpools/CachedThreadPool.java

@@ -0,0 +1,16 @@
+package com.baeldung.concurrent.threads.create.threadpools;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class CachedThreadPool {
+    public static void main(String[] args){
+        ExecutorService executorService = Executors.newCachedThreadPool();
+        executorService.submit(()->{
+            System.out.println("submitted a runnable task to cached thread pool");
+            System.out.println(Thread.currentThread().getName()+" from pool is executing the task");
+        });
+
+        executorService.shutdown();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/threadpools/FixedThreadPool.java

@@ -0,0 +1,17 @@
+package com.baeldung.concurrent.threads.create.threadpools;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class FixedThreadPool{
+
+    public static void main(String[] args){
+        ExecutorService executorService = Executors.newFixedThreadPool(5);
+        executorService.submit(()->{
+            System.out.println("submitted a runnable task to fixed thread pool");
+            System.out.println(Thread.currentThread().getName()+" from pool is executing the task");
+        });
+
+        executorService.shutdown();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/threadpools/ScheduledThreadPool.java

@@ -0,0 +1,14 @@
+package com.baeldung.concurrent.threads.create.threadpools;
+
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+public class ScheduledThreadPool{
+    public static void main(String[] args){
+        ScheduledExecutorService executorService = Executors.newScheduledThreadPool(3);
+        executorService.schedule(()->System.out.println("executing scheduled runnable task"), 5, TimeUnit.SECONDS);
+
+        executorService.shutdown();
+    }
+}

core-java-modules/core-java-concurrency-basic-2/src/main/java/com/baeldung/concurrent/threads/create/threadpools/SingleThreadPool.java

@@ -0,0 +1,20 @@
+package com.baeldung.concurrent.threads.create.threadpools;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+public class SingleThreadPool{
+    public static void main(String[] args){
+        ExecutorService executorService = Executors.newSingleThreadExecutor();
+        try{
+            Future<String> result = executorService.submit(()-> "callable task executed");
+            System.out.println(result.get());
+        }catch(InterruptedException | ExecutionException e){
+            e.printStackTrace();
+        }
+
+        executorService.shutdown();
+    }
+}