Java concurrency: A thread A calls wait(2000) inside a synchronized method on object B. When does thread A become eligible (a candidate) to run again?

Introduction / Context:Timed waiting with wait(timeout) is a core synchronization mechanism in Java. Knowing precisely when a waiting thread can proceed is key to designing correct monitors.

Given Data / Assumptions:

• Thread A executed wait(2000) while holding B’s monitor (inside synchronized code on B).
• Calling wait releases the monitor and suspends A.
• Other threads may call notify() or notifyAll() on B.

Concept / Approach:With wait(timeout), a thread stops waiting when either it is notified or the timeout elapses. After that, it must re-acquire B’s monitor before resuming running. The question asks when it becomes a candidate for CPU time, which is upon notification or timeout expiration.

Step-by-Step Solution:

Verification / Alternative check:Even after notification/timeout, progress depends on re-acquiring B’s lock; however, eligibility begins at notify/timeout boundaries.

Why Other Options Are Wrong:

• Option B over-emphasizes lock release as the trigger; the primary triggers are notify or timeout.
• Options C and D misstate sequencing and conditions.

Common Pitfalls:Confusing “eligible to run” with “actively running.” Lock reacquisition is still required after notify/timeout.

Final Answer:After thread A is notified, or after two seconds.