Java 21 Virtual Threads 🎯

Welcome to our comprehensive guide on Java Virtual Threads! We're thrilled to have you here as we delve into this fascinating topic. Whether you're a beginner just starting your coding journey or an intermediate looking to expand your skillset, this tutorial is designed to cater to both. Let's get started!

What are Virtual Threads? 📝

Virtual Threads, introduced in Java 15 and improved in Java 17, are not actual threads as we know them but rather a lightweight abstraction of threads. They are a way to create more threads without incurring the overhead of creating and managing native OS threads.

Why Virtual Threads? 💡

Virtual Threads offer several advantages over traditional threads:

Reduced Overhead: Since they are not actual OS threads, they consume less memory and CPU resources.
Simplicity: Developers don't need to manually manage thread pools or synchronization issues.
Scalability: With fewer resources consumed, more virtual threads can be created for better scalability.

Creating Virtual Threads 💡

Creating a Virtual Thread is as simple as creating a regular method:

java

// Create a virtual thread
var vt = () -> {
    // Virtual thread code goes here
};

// Start the virtual thread
vt.start();

💡 Pro Tip: Virtual threads are started with the start() method, just like regular threads.

Synchronization and Cooperation 📝

Unlike regular threads, virtual threads don't have an intrinsic concept of synchronization. Instead, they rely on the existing synchronization primitives such as synchronized blocks, Lock objects, and Condition objects.

Examples 💡

Example 1: Simple Virtual Thread

java

public class SimpleVirtualThread {
    public static void main(String[] args) {
        // Create a virtual thread
        var vt = () -> {
            System.out.println("Hello from Virtual Thread!");
        };

        // Start the virtual thread
        vt.start();
    }
}

Example 2: Synchronized Virtual Threads

java

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class SynchronizedVirtualThread {
    private static final Lock lock = new ReentrantLock();
    private static int counter = 0;

    public static void main(String[] args) throws InterruptedException {
        // Create and start two virtual threads
        var vt1 = () -> {
            for (int i = 0; i < 1000000; i++) {
                lock.lock();
                try {
                    counter++;
                } finally {
                    lock.unlock();
                }
            }
        };

        var vt2 = () -> {
            for (int i = 0; i < 1000000; i++) {
                lock.lock();
                try {
                    counter++;
                } finally {
                    lock.unlock();
                }
            }
        };

        var thread1 = new Thread(vt1);
        var thread2 = new Thread(vt2);

        thread1.start();
        thread2.start();

        thread1.join();
        thread2.join();

        System.out.println("Counter: " + counter);
    }
}

Quiz 💡

We hope you enjoyed learning about Java Virtual Threads! In the next lesson, we'll dive deeper into using and managing virtual threads in your projects. Happy coding! 🎉