OCP Java Concurrency 3

Question 1

Which `java.util.concurrent.atomic` class provides an atomic reference to an object that can be updated using compare-and-swap?

Accepted Answer

AtomicReference

Answer

`AtomicReference<V>` wraps an object reference and provides atomic CAS operations via `compareAndSet()`.

Question 2

What is a happens-before relationship in the Java Memory Model?

Accepted Answer

A guarantee that results of action A are visible to action B if A happens-before B

Answer

The happens-before relationship guarantees that memory writes by one action are visible to another action that follows it in the happens-before order.

Question 3

What exception is thrown when a thread waiting on a `Future.get()` is interrupted?

Accepted Answer

InterruptedException

Answer

`Future.get()` throws `InterruptedException` if the current thread is interrupted while waiting for the computation.

Question 4

Which method of `Semaphore` acquires a permit, blocking until one is available or the thread is interrupted?

Accepted Answer

acquire()

Answer

`acquire()` blocks indefinitely until a permit is available or the calling thread is interrupted.

Question 5

In a `ForkJoinPool`, what does a worker thread do when its own deque is empty?

Accepted Answer

Steals tasks from the tail of another worker's deque

Answer

Work-stealing allows idle workers to steal tasks from the tail (opposite end) of busy workers' deques to maximize CPU utilization.

(OCP) Oracle Certified Professional Practice Test

(OCP) Oracle Certified Professional Practice Test

OCP Java Concurrency 3