Java / Java 21 Virtual Threads Interview questions
Explain the lifecycle of a virtual thread?
A virtual thread moves through the same Thread.State enum as a platform thread, but the transitions are driven by the JVM scheduler rather than the OS.
stateDiagram-v2
[*] --> NEW
NEW --> RUNNABLE : start()
RUNNABLE --> RUNNING : mounted on a carrier
RUNNING --> WAITING : blocking call, park(), or lock wait
WAITING --> RUNNABLE : condition satisfied, rescheduled
RUNNING --> TERMINATED : run() completes or throws
TERMINATED --> [*]
It starts NEW, becomes RUNNABLE once submitted to the scheduler, transitions to effectively running once mounted onto a carrier, moves to a waiting state whenever it's unmounted for a blocking operation, and finally reaches TERMINATED once its task completes. Unlike a platform thread, the mount/unmount cycle can repeat many times across different carriers during a single virtual thread's life.
A virtual thread's lifecycle uses:
During its life, a virtual thread's mount/unmount cycle can:
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