Understanding Java Virtual Threads | Java 21, 20, 19 | Made Easy

What is a Virtual Thread?
Like a platform thread, a virtual thread is also an instance of java.lang.Thread. However, a virtual thread isn't tied to a specific OS thread. A virtual thread still runs code on an OS thread. However, when code running in a virtual thread calls a blocking I/O operation, the Java runtime suspends the virtual thread until it can be resumed. The OS thread associated with the suspended virtual thread is now free to perform operations for other virtual threads.
Virtual threads are implemented in a similar way to virtual memory. To simulate a lot of memory, an operating system maps a large virtual address space to a limited amount of RAM. Similarly, to simulate a lot of threads, the Java runtime maps a large number of virtual threads to a small number of OS threads. Unlike platform threads, virtual threads typically have a shallow call stack, performing as few as a single HTTP client call or a single JDBC query. Although virtual threads support thread-local variables, you should carefully consider using them because a single JVM might support millions of virtual threads. Virtual threads are suitable for running tasks that spend most of the time blocked, often waiting for I/O operations to complete. However, they aren't intended for long-running CPU-intensive operations.
JEP : openjdk.org/je...
OpenJDK : openjdk.org/
Tags : #java #openjdk #jdk20 #jdk21 #jdk19 #java #javabasics #javaconcepts #javaprogramming #javamultithreading #RoadTo21

[@zeppelinmexicano]

Java has come a long way, baby. Virtual threads, streams, lambdas, even a new switch, just in the last few years. When you factor in the enormous base and the fact that it just works, even if more verbose than some of the newer languages, it's a pretty undeniable force of coding nature. I remember all the "Java killer" threats coming out of MS when dotNet was released. Pure marketing bullshit.

[@Pyrotiksilence]

20mb per platform thread is not accurate. It’s typically going to be closer to 1-2mb to create a platform thread in Java.

[@ShreeGodmeshwarEnterprises]

Can't wait to implement this virtual thread into live project

[@vikrantdhawan4062]

Great video!! just a suggestion , some intro about video will help lister to understand now content is starting be ready

[@SmartDev-jl1wp]

Create videos on Java features as well

[@MadeEasyTech]

Sure

[@tirunagariuttam]

@MadeEasyTech I liked the way you explained the topic. Please do make a full video on core java. Thanks.

[@francisantony12]

This was a very good presentation. Thank You

[@MadeEasyTech]

Glad you enjoyed it!

[@djricky89999]

Sorry consist threads in the cpu??

[@santhoshkrishnan5568]

20 MB per platform thread?

[@developer-zl8xt]

Really helpful

[@thangamanikasi]

Awesome... Thanks... Could you please share the github URL for this source code?

[@khmarbaise]

Congrats on that great video. Thank you.

[@longshin4299]

1 Thread 20MB memory or 2MB?

[@chamanjain9843]

I have a question. Suppose I made an HTTP request using Java from a virtual thread, let's say using RestTemplate. Now, suppose that the response takes approximately 2 minutes. Does this mean the virtual thread will release this platform thread and OS thread and itself get blocked for the duration of 2 minutes? Assuming the response arrives on port 8080, will it directly notify the virtual thread that the response has arrived, prompting it to wake up? Or will there be some OS thread that handles the response first and then informs the platform thread to wake up the virtual thread?

[@alessioantinoro5713]

Platform thread and os thread are (almost) the same thing. Then, in case on any blocking operation, the platform thread is released to be re-used anywhere, while the code blocks and waits, once the request completes, the virtual thread will receive a new available platform thread and continue it's execution. The os has no idea this happened, only the JVM knows. Too there are some operation (like the synchronized block) that will block the platform thread until the request is done.

[@priyankagutte8175]

very nice video, keep it up

[@devilhorrible6715]

Can you share the code snippet???

[@vikrantdhawan4062]

Can I work with your on these videos

[@imranmomin4571]

It occupy 2MB not 20MB.

[@PixelHamster]

What are you using for TTS ?

[@djricky89999]

If I have virtual theads for example in my laptop I have 16gb of ram and I create virtual threads, how much 16gb of ram? Or do I create more? Will I have more speed for my heavy programmes? Explain to me well!

[@dev50107]

Awesome ❤

[@ravibmsit]

Excellent content .. To the point and very high quality narration !! Thanks for sharing this knowledge with us :)

[@priyagutte293]

👍 yeah

[@anonymous83245]

Q: how the cpu usage is calculated? A: total CPU usage = threads num * (computation time per thread / total time per thread) ; so the total cpu usage in this video: 0.8% ≈ 800 * ((500ns + 500ns) / (100ms * 1000000 + (500ns + 500ns)))

[@k2ketan100]

It takes 1mb for 64bit jvm per thread

[@grzegorzt5245]

why 20MB per thread ?

[@hfislwpa]

Great video thank you!

[@MadeEasyTech]

Glad you liked it!

[@techlover551]

I can see that your content quality is improving. Keep it going.

[@MadeEasyTech]

I appreciate that!