Let’s be honest, multithreading has always been a bit of a heavy topic. Many developers, especially beginners, get confused when they hear terms like threads, context switching, or concurrent programming. But what if we told you there’s a new way to handle thousands of tasks in Java in a lightweight, efficient, and developer-friendly way? That’s where Virtual Threads in Java shines.

Welcome to Virtual Threads – a game-changing feature that brings massive scalability to Java applications without making your head spin.

In this article, we’ll walk you through everything step by step. From the basics of multitasking to how virtual threads solve real-world problems. All in simple Indian English, no complex jargon. Let’s begin!

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1. How Computers Handle Multiple Tasks

Forget about multithreading for now. Imagine your computer has only one CPU core. Still, you’re able to run multiple apps like Photoshop, Paint, and Notepad at the same time. How is that possible?

This works because of a concept called time-slicing. Your CPU switches quickly between different tasks, giving a small time slice to each. First Photoshop, then Paint, then Notepad, and so on. It switches so fast that it feels like everything is running at once, but technically only one task is active at any given moment.

Now imagine your computer has 4 CPU cores. Each core can run one task in parallel. So 4 different tasks can truly run at the same time. Even better, each core can still do time-slicing between more tasks if needed. That’s the real power of multi-core processors.

2. What Is Multithreading?

If your program does only one thing at a time, it is called a single-threaded program. But modern applications usually need to do many things at the same time – like downloading a file while showing a progress bar, or reading a file while updating the screen.

This is where threads come in. Your program can split itself into smaller tasks that can run independently. Each of these parts is a thread. So, if one thread is downloading a file, another can be updating the UI without waiting.

Let’s take an example. You are using a browser like Chrome. At one time, one tab is downloading a file, another is rendering a web page, and another is playing a YouTube video. All these are happening together. That’s multithreading in action.

3. Traditional Threads (Platform Threads)

In Java, when you create a new thread, the JVM asks the Operating System (OS) to create it. These are called platform threads, also known as native or kernel threads.

The OS manages everything about these threads – it creates them, destroys them, decides when they should run, and switches between them. But this management has a cost.

• Each OS thread uses its own memory, especially for the stack. In Java, default stack size is around 1MB.
• If you create 10,000 threads, you need around 10 GB just for thread stacks. That’s a lot.
• Context switching between threads is slow and consumes CPU power.

So, if your Java application needs to handle thousands of requests at once, like a web server or backend service, platform threads are not ideal. They consume too much memory and CPU, even when they are just sitting idle waiting for something, like a response from a database or an API.

4. The Problem with Blocking

Let’s say your Java web server (maybe Spring Boot) handles 10,000 requests. Each request:

1. Makes a database call (which takes 200 ms)
2. Waits for a payment gateway API
3. Returns a response to the user

Now during step 1 and 2, your thread is just waiting. But even while waiting, it is holding memory and CPU scheduling time. It’s not doing any real work, yet it’s consuming resources.

This is a huge waste. Because I/O tasks like DB/API calls are not CPU-heavy. They mostly involve waiting. Why should we use heavyweight threads just to wait?

5. Introducing Virtual Threads in Java

This is exactly where Virtual Threads come in. Introduced in Java as part of Project Loom, virtual threads solve this problem beautifully.

What are they? Virtual threads are lightweight threads that are managed by the JVM instead of the OS. They are very cheap to create and you can easily create thousands of them.

Internally, they still use platform threads, but only when needed. Here’s how it works:

1. You start a virtual thread for a request.
2. When the thread makes a blocking call (like DB/API), the JVM parks the virtual thread and frees the platform thread.
3. Once the response comes, the JVM resumes the virtual thread on any available platform thread.

This means the real OS threads are not blocked unnecessarily. And the virtual threads don’t use memory or CPU while waiting. Beautiful, isn’t it?

6. Virtual Threads in Java : What About Code Changes?

The best part is – your code mostly stays the same. No need to learn reactive programming or use complex async libraries. You write the same logic you always wrote.

Only difference is how you start the thread:

Thread.startVirtualThread(() -> {
    // your code here
});

That’s it. If your code calls a blocking API or DB, JVM will handle it smartly. If your code is CPU-heavy, it will still use a platform thread, which is fine because real work needs real CPU.

7. Benefits of Virtual Threads in Java

• Massive scalability: You can handle 100,000+ concurrent tasks.
• Simple code: No need for reactive or complex async code.
• Better memory usage: No 1MB per thread stack.
• Efficient CPU usage: No waste on context switching or idle threads.

8. When Should You Use Virtual Threads In Java?

They are best suited for I/O-bound applications like:

• Web servers
• Microservices
• Applications that make many API or DB calls

If your application is mostly doing CPU-bound tasks (like video processing, number crunching, etc.), virtual threads won’t give much benefit. But for modern backend applications, they are a perfect match.

Final Thoughts

Virtual threads bring a big shift in how we think about concurrency in Java. But the beauty is – the shift in your code is very small.

For developers, it means writing simple, readable code that can scale like crazy. For Java itself, it means it’s ready for the future of cloud, servers, and microservices.

So, should you start using virtual threads? Absolutely yes, especially if you are building applications that handle lots of user requests.

Hope this article helped you understand the concept clearly. If you liked this, do check out my courses for more practical and beginner-friendly Java content.