Scala Test 1

Question 1

Which of the following expressions has the proper value?
List(1,2,3)flatMap(x=>List(x,4))

Accepted Answer

List(1,4,2,4,3,4)

Answer

The `flatMap` function in Scala applies a given function to each element of a collection, which returns a new collection for each element, and then flattens all these resulting collections into a single one. For `List(1,2,3).flatMap(x => List(x,4))`, each number `x` is transformed into `List(x,4)`. This results in `List(1,4)`, `List(2,4)`, and `List(3,4)`, which are then concatenated to form `List(1,4,2,4,3,4)`.

Question 2

Scala is also known as:

Accepted Answer

Scripting Language

Answer

Scala is a powerful, general-purpose programming language that runs on the JVM, supporting both object-oriented and functional paradigms. Due to its concise syntax and the availability of an interactive interpreter (REPL), Scala can also be effectively used for scripting tasks, allowing developers to write and execute code quickly without the full compilation process typically associated with larger applications.

Question 3

Which of the following claims regarding Either is correct?

Accepted Answer

All of the above

Answer

In Scala, `Either[L, R]` is a sealed abstract class that represents a value which can be of type `L` (typically for 'Left' or error) or type `R` (typically for 'Right' or success). This makes it a powerful tool for error handling and dealing with optional or potentially missing values, as it explicitly forces the developer to consider both possible outcomes. Therefore, all the given statements accurately describe `Either`.

Question 4

Case classes are Left and Right. Is this statement true or false?

Accepted Answer

True

Answer

In Scala's `Either` type, `Left` and `Right` are indeed case classes. They serve as concrete implementations of the `Either` abstract class, allowing an `Either` instance to encapsulate a value of either the 'left' type or the 'right' type. This design facilitates pattern matching, enabling developers to elegantly handle both success and failure scenarios.

Question 5

Choose the appropriate value from the following line of code:
"abcde" ensures that (_.length>3)

Accepted Answer

abcde

Answer

The `ensure` method in Scala checks if a given predicate holds true for the value it's called on. If the predicate evaluates to `true`, the original value is returned. If it's `false`, an `IllegalArgumentException` is thrown. In this case, the string "abcde" has a length of 5, and the condition `(_.length > 3)` (5 > 3) is true, so the original string "abcde" is returned.

Scala Practice Test

Scala Practice Test

Scala Test 1