OCP Java Concurrency 2

Question 1

Which method of the `CountDownLatch` class blocks the calling thread until the count reaches zero?

Accepted Answer

await()

Answer

countDown()

Answer

reset()

Answer

getCount()

Question 2

What happens when a thread calls `CyclicBarrier.await()` and it is the last thread to arrive at the barrier?

Accepted Answer

It triggers the optional barrier action and releases all waiting threads

Answer

It blocks until an external thread calls reset()

Answer

It throws a BrokenBarrierException

Answer

It silently exits without releasing others

Question 3

Which `ExecutorService` method submits a `Callable` and returns a `Future` representing the pending result?

Accepted Answer

submit(Callable)

Answer

execute(Runnable)

Answer

invokeAll(Collection)

Answer

schedule(Callable, long, TimeUnit)

Question 4

What is the purpose of the `volatile` keyword in Java concurrency?

Accepted Answer

Ensures visibility of variable changes across threads without atomicity guarantees

Answer

Makes a variable immutable

Answer

Prevents two threads from accessing a variable simultaneously

Answer

Provides atomic compound operations on a variable

Question 5

Which class in `java.util.concurrent` provides a resizable-array implementation of a blocking queue?

Accepted Answer

LinkedBlockingQueue

Answer

ArrayBlockingQueue

Answer

SynchronousQueue

Answer

PriorityBlockingQueue

Question 6

What does `Future.cancel(true)` do to a running task?

Accepted Answer

Attempts to interrupt the thread executing the task

Answer

Immediately terminates the thread

Answer

Waits for the task to complete then marks it cancelled

Answer

Throws an exception in the task's thread

Question 7

Which `ReentrantLock` feature allows a thread to acquire the lock only if it is not held by another thread at the time of invocation?

Accepted Answer

tryLock()

Answer

lockInterruptibly()

Answer

lock()

Answer

newCondition()