Unlocking Performance: Exploring Java 21 Virtual Threads [Video]

In this Java 21 tutorial, we dive into virtual threads, a game-changing feature for developers. Virtual threads are a lightweight and efficient alternative to traditional platform threads, designed to simplify concurrent programming and enhance the performance of Java applications. In this article, we’ll explore the ins and outs of virtual threads, their benefits, compatibility, and the migration path to help you leverage this powerful Java 21 feature.

Introducing Virtual Threads

Virtual threads represent a significant evolution in the Java platform’s threading model. They are designed to address the challenges of writing, maintaining, and optimizing high-throughput concurrent applications. It’s essential to differentiate virtual threads from traditional platform threads to understand them.

In traditional Java, every instance of java.lang.Thread is a platform thread. A platform thread runs Java code on an underlying OS thread and occupies that OS thread for the duration of its execution. It means that the number of platform threads is limited to the number of available OS threads, leading to potential resource constraints and suboptimal performance in highly concurrent applications.

On the other hand, a virtual thread is also an instance of java.lang.Thread, but it operates differently. Virtual threads run Java code on an underlying OS thread without capturing the OS thread for its entire lifecycle. This crucial difference means multiple virtual threads can share the same OS thread, offering a highly efficient way to utilize system resources. Unlike platform threads, virtual threads do not monopolize precious OS threads, which can lead to a significantly higher number of virtual threads than the number of available OS threads.

The Roots of Virtual Threads

Virtual threads draw inspiration from user-mode threads, successfully employed in other multithreaded languages such as Go (with goroutines) and Erlang (with processes). In the early days of Java, user-mode threads were implemented as “green threads” due to the immaturity and limited support for OS threads. These green threads were eventually replaced by platform threads, essentially wrappers for OS threads, operating under a 1:1 scheduling model.

Virtual threads take a more sophisticated approach, using an M:N scheduling model. In this model, many virtual threads (M) are scheduled to run on fewer OS threads (N). This M:N scheduling approach allows Java applications to achieve a high concurrency level without the resource constraints typically associated with platform threads.

Leveraging Virtual Threads

In Java 21, developers can easily harness the power of virtual threads. A new thread builder is introduced to create virtual and platform threads, providing flexibility and control over the threading model.

To create a virtual thread, you can use the following code snippet:

Thread.Builder builder = Thread.ofVirtual().name("Virtual Thread");
Runnable task = () -> System.out.println("Hello World");
Thread thread = builder.start(task);
System.out.println(thread.getName());
thread.join();

It’s important to note that virtual threads are significantly cheaper in terms of resource usage when compared to platform threads. You can create multiple virtual threads, allowing you to exploit the advantages of this new threading model fully:

Thread.Builder builder = Thread.ofVirtual().name("Virtual Thread", 0);
Runnable task = () -> System.println("Hello World: " + Thread.currentThread().threadId());

Thread thread1 = builder.start(task);
Thread thread2 = builder.start(task);
thread1.join();
thread2.join();

Virtual threads can also be effectively utilized with the ExecutorService, as demonstrated in the code below:

try (ExecutorService executor = Executors.newVirtualThreadPerTaskExecutor()) {
    Future<String> future = executor.submit(() -> "Hello World");
    System.out.println(future.get());
    System.println("The end!");
}

The Virtual vs. Platform Thread Trade-Off

It’s crucial to understand that platform threads are not deprecated in Java 21, and virtual threads are not a one-size-fits-all solution. Each type of thread has its own set of trade-offs, and the choice between them should be made based on your application’s specific requirements.

• Virtual threads: Virtual threads are excellent for high-throughput concurrent tasks, especially when managing many lightweight threads without OS thread limitations. They are well-suited for I/O-bound operations, event-driven tasks, and workloads with many short-lived threads.
• Platform threads: Platform threads are still valuable for applications where fine-grained control over thread interactions is essential. They are ideal for CPU-bound operations, real-time applications, and scenarios that require precise thread management.

In conclusion, Java 21’s virtual threads are a groundbreaking addition to the Java platform, offering developers a more efficient and scalable way to handle concurrency. By understanding the differences and trade-offs between virtual and platform threads, you can make informed decisions on when and how to leverage these powerful features to unlock the full potential of your Java applications.

Video

References

• Source
• JPE