Java Basics: What are Virtual Threads?

Virtual threads are lightweight threads that simplify writing and maintaining concurrent applications with high compute requirements.   

Traditional platform threads are very heavy, i.e., they use a significant amount of compute resources, and are bound 1:1 to the OS thread, which means that execution time of the threads is dependent on the CPU’s execution time.  

Each of these threads would end up utilizing as much as 10 GB of memory; this adds up quickly depending on any level of complexity implemented in your application. These threads were designated to use a single thread with every request. While traditional threads provide a level of simplicity for developing applications, the lack of flexibility often resulted in large applications being negatively impacted by the amount of requests made by the code. 

Virtual threads, on the other hand, move the responsibility of scheduling threads from the OS to the JVM (Java Virtual Machine), effectively introducing an abstraction layer between the OS and the application.  

Virtual threads were created with a few distinct purposes in mind. First, they enable Java developers to write server applications using a simple thread-per-request style. Second, virtual threads enable Java developers to utilize hardware to the fullest extent possible by eliminating the OS as the limiting factor to performance.  

🆕 Tomcat 11 includes virtual thread support. Learn more in this blog from our friends at OpenLogic. 

Example of Virtual Thread 

Runnable fn = () -> { // code};  

Thread thread = Thread.ofVirtual(fn) .start(); 

Thread thread = Thread.startVirtualThread(() -> { //code }); 

How Virtual Threads Became a Permanent JDK Feature