Structured Concurrency in Java

// Java Program to demonstrate structured concurrency in
// Java using the ExecutorService and CompletableFuture
// classes from the java.util.concurrent package.
import java.util.concurrent.*;

// Driver class
public class StructuredConcurrencyExample {

    // function main
    public static void main(String[] args)
        throws InterruptedException, ExecutionException
    {
        ExecutorService executor
            = Executors.newFixedThreadPool(3);

        CompletableFuture<Void> task1
            = CompletableFuture.runAsync(() -> {
                  System.out.println("Task 1 started");
                  // Perform task 1
              }, executor);

        CompletableFuture<Void> task2
            = CompletableFuture.runAsync(() -> {
                  System.out.println("Task 2 started");
                  // Perform task 2
              }, executor);

        CompletableFuture<Void> combinedTasks
            = CompletableFuture.allOf(task1, task2);
        // Waits for both tasks to complete
        combinedTasks.get();

        executor.shutdown();
    }
}

// Java program to demonstrate the use of the ForkJoinPool
// to create organized concurrent tasks.
import java.util.concurrent.*;

public class StructuredConcurrencyExample {
    public static void main(String[] args)
    {
        ForkJoinPool forkJoinPool = new ForkJoinPool();

        // Task 1
        RecursiveAction task1 = new RecursiveAction() {
            @Override protected void compute()
            {
                // Perform task 1
                System.out.println("Task 1 started");
            }
        };

        // Task 2
        RecursiveAction task2 = new RecursiveAction() {
            @Override protected void compute()
            {
                // Perform task 2
                System.out.println("Task 2 started");
            }
        };

        // Submit both tasks and then join them
        ForkJoinTask<Void> submittedTask1
            = forkJoinPool.submit(task1);
        ForkJoinTask<Void> submittedTask2
            = forkJoinPool.submit(task2);

        // Wait for both tasks to complete
        submittedTask1.join();
        submittedTask2.join();

        forkJoinPool.shutdown();
    }
}