A runtime and concurrency self-check tests visibility, resource closure, reflection and worker completion.
Review the contracts
Review atomic transitions, reflection failures, resource closure before answering.
Choose and explain an answer
Separate visibility, atomicity and successful completion. For reflection, distinguish the wrapper exception from the exception thrown by the target method.
Select an answer for every question, then check the result and read each explanation. Progress remains in this browser; this is a self-check, not a judged program submission or a credential.
Common Mistakes
A volatile field does not make a read-modify-write sequence atomic. Successful submission does not prove completed work.