Also note that after a thread calls start(), subsequent calls to that method before the run() method exits cause start() to throw a java.lang.IllegalThreadStateException object.

Virtual threads take the responsibility for allocating system resources out of your application code and into the JVM. Here's a first look at virtual threads in Java 21.

Java achieved write-once, run-anywhere for concurrent programs by ensuring that the language and APIs provided a complete, portable abstraction for threads, inter-thread coordination mechanisms ...

JDK 21's virtual threads are a major leap forward for Java's concurrency model. Previously, Java relied on OS threads, which were resource-heavy, limiting how many threads could run concurrently.