“The JDK can now run up to 10,000 concurrent virtual threads on a small number of operating system (OS) threads, as little as one, to execute the simple code above that involves sleeping for one second.”
Java gets virtual threads in JDK 21 after two preview rounds in JDK 19 and 20. The demo is 10,000 threads that all sleep for a second, the easiest workload in computing. The fine print covers pinning, thread-local variables to use “with caution,” and source and binary incompatible changes for code that extends Thread. JMX still only sees platform threads.