Application.java

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class Application {

    public static void main(String[] args) throws InterruptedException {
        System.out.println("main thread is started");

        ExecutorService executorService = Executors.newCachedThreadPool();
        CountDownLatch countDownLatch = new CountDownLatch(10);

        List<Callable<String>> allCallableList = new ArrayList<>();

        for (int taskIndex = 0; taskIndex < 10; taskIndex++) {
            //creating the callable object
            Callable<String> callable = () -> {
                System.out.println("Thread [" + Thread.currentThread().getName() + "] is executing the task");
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    System.out.println("sleeping thread get interrupted");
                }
                countDownLatch.countDown();
                return "done";
            };

            allCallableList.add(callable);
        }

        //execute all the callables in background threads
        executorService.invokeAll(allCallableList);
        countDownLatch.await();

        System.out.println("main thread completed ");
    }
}