Scala Concurrency and Futures 2

Question 1

What happens when you call `Await.result` in Scala?

Accepted Answer

It blocks the current thread until the Future completes or a timeout elapses

Answer

`Await.result(future, duration)` blocks the calling thread until the Future completes, returning the value or throwing an exception.

Question 2

What is `flatMap` used for with Scala Futures?

Accepted Answer

Chaining asynchronous operations where each step depends on the previous result

Answer

`flatMap` on a Future chains a dependent asynchronous operation, allowing sequential async steps without deeply nested callbacks.

Question 3

How do you recover from a failed Scala Future?

Accepted Answer

future.recover { case e: SomeException => defaultValue }

Answer

`recover` applies a partial function to a failed Future, returning a successful Future with a default value if the pattern matches.

Question 4

What is a `for-comprehension` over Futures equivalent to in Scala?

Accepted Answer

Chaining flatMap and map calls for sequential async composition

Answer

A `for-comprehension` over Futures desugars into `flatMap` and `map` calls, composing sequential asynchronous operations in a readable syntax.

Question 5

What does `Future.successful(value)` create?

Accepted Answer

An already-completed successful Future wrapping the given value

Answer

`Future.successful(value)` creates an immediately completed Future without scheduling any asynchronous computation.

Scala Practice Test