Demystifying Virtual Threads

Java 21 introduces a game-changer for concurrent programming: virtual threads. This article explores what virtual threads are and how they can revolutionize the way you build high-performance applications.

Traditional Threads vs. Virtual Threads

Java developers have long relied on platform threads, the fundamental unit of processing that runs concurrently. However, creating and managing a large number of platform threads can be resource-intensive. This becomes a bottleneck for applications handling high volumes of requests.

Virtual threads offer a lightweight alternative. They are managed by the Java runtime environment, allowing for a much larger number to coexist within a single process compared to platform threads. This translates to significant benefits:

• Reduced Overhead: Creating and managing virtual threads requires fewer resources, making them ideal for applications that thrive on high concurrency.
• Efficient Hardware Utilization: Virtual threads don't directly map to operating system threads, enabling them to better leverage available hardware cores. This translates to handling more concurrent requests and improved application throughput.
• Simpler Concurrency Model: Virtual threads adhere to the familiar "one thread per request" approach used with platform threads. This makes the transition for developers already comfortable with traditional concurrency patterns much smoother. There's no need to learn entirely new paradigms or complex APIs.

Creating Virtual Threads

Java 21 offers two primary ways to create virtual threads:

1. Thread.Builder Interface: This approach provides a familiar interface for creating virtual threads. You can use a static builder method or a builder object to configure properties like thread name before starting it.

   Here's an example of using the Thread.Builder interface:

   Runnable runnable = () -> {
      var name = Thread.currentThread().getName();
      System.out.printf("Hello, %s!%n", name.isEmpty() ? "anonymous" : name);
   };
   
   try {
      // Using a static builder method
      Thread virtualThread = Thread.startVirtualThread(runnable);
   
      // Using a builder with a custom name
      Thread namedThread = Thread.ofVirtual()
              .name("my-virtual-thread")
              .start(runnable);
   
      // Wait for the threads to finish (optional)
      virtualThread.join();
      namedThread.join();
   } catch (InterruptedException e) {
      throw new RuntimeException(e);
   }

2. ExecutorService with Virtual Threads: This method leverages an ExecutorService specifically designed to create virtual threads for each submitted task. This approach simplifies thread management and ensures proper cleanup of resources.

   Here's an example of using an ExecutorService with virtual threads:

   try (ExecutorService myExecutor = Executors.newVirtualThreadPerTaskExecutor()) {
      Future future = myExecutor.submit(() -> System.out.println("Running thread"));
      future.get(); // Wait for the task to complete
      System.out.println("Task completed");
   } catch (ExecutionException | InterruptedException e) {
      throw new RuntimeException(e);
   }

Embrace a New Era of Concurrency

Virtual threads represent a significant leap forward in Java concurrency. Their efficiency, better hardware utilization, and familiar approach make them a powerful tool for building high-performance and scalable applications.