SCJP Java Threads and Concurrency 5

Question 1

What is the role of the `Executor` framework in Java concurrency?

Accepted Answer

It provides a higher-level API for managing thread creation and execution

Answer

The `Executor` framework decouples task submission from thread management, enabling thread pooling and flexible execution policies.

Question 2

Which interface must be implemented to submit a task to an `ExecutorService` that returns a result?

Accepted Answer

Callable

Answer

`Callable<V>` is like `Runnable` but its `call()` method returns a value and can throw checked exceptions.

Question 3

A thread is in the TIMED_WAITING state. Which call most likely caused this?

Accepted Answer

synchronized(obj) { obj.wait(5000); }

Answer

Calling `wait(timeout)` with a positive timeout places the thread in TIMED_WAITING until the timeout expires or it is notified.

Question 4

What exception is thrown when a thread that is blocked in `sleep()` or `wait()` has its `interrupt()` method called?

Accepted Answer

InterruptedException

Answer

`InterruptedException` is a checked exception thrown when a thread's interrupted status is set while it is blocked in a wait, sleep, or join.

Question 5

Which `java.util.concurrent` class implements a blocking queue that can be used for producer-consumer problems?

Accepted Answer

LinkedBlockingQueue

Answer

`LinkedBlockingQueue` blocks the producer when full and the consumer when empty, making it ideal for producer-consumer scenarios.

SCJP - Sun Certified Java Programmer Practice Test