Java Threads and Concurrency Flashcards

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

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

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

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

Answer: Callable

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

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

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

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

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

Answer: InterruptedException

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

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

Answer: LinkedBlockingQueue

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

What does the `join()` method on a Thread object do?

Answer: Causes the calling thread to wait until the target thread has finished executing

Calling `threadA.join()` blocks the calling thread until `threadA` completes, allowing threads to coordinate completion order.

Which statement about the `synchronized` keyword applied to a static method is correct?

Answer: It locks on the Class object associated with the declaring class

A synchronized static method acquires the intrinsic lock on the `Class` object, so all instances share the same lock for that method.