Scala Programming Quiz Questions and Answers

println is a built-in function in Scala that prints the given argument followed by a newline to the standard output, which is typically the console. It’s a side-effecting function, meaning it changes the state of the world outside the function (in this case, the console).

val is used to declare a variable that is immutable, meaning its value cannot be changed once assigned. This is in contrast to var, which declares a mutable variable. Immutability is a key feature of functional programming, which Scala supports.

Functions in Scala are defined using the def keyword, followed by the function name, parameters (if any), and the function body. The return type of the function can be inferred by the compiler, or explicitly stated after a colon.

A case class in Scala is a special kind of class that comes with some useful default methods and can be used in pattern matching, can handle exceptions, and can be serialized. Case classes are good for modeling immutable data and are automatically equipped with natural equality, a nice toString method, and the ability to be used in “match” expressions.

trait in Scala is a type of interface that can have both abstract and non-abstract methods. It’s similar to an interface in Java, but with more features. Traits can be mixed into classes to provide additional functionality, and they can also require that a certain interface be implemented.

ArrayBuffer in Scala is a mutable collection that represents an array. It provides constant time access and modification of elements. This is in contrast to List, which provides constant time access and modification at the front of the list, but not at the end or in the middle.

List in Scala is an immutable collection that represents a linked list. Once a List is created, it cannot be changed. This is in contrast to ArrayBuffer, which is a mutable collection. Immutable collections are safe to use in a multi-threaded environment, as they can’t be changed after they’re created.

Unit in Scala is a subtype of AnyVal and is used to represent a value that carries no meaningful information. It’s similar to void in Java. It’s used as the return type of a method that doesn’t return a meaningful value.

Option in Scala represents optional values. It can either contain a value (Some) or no value (None). It’s a way of dealing with null values, avoiding NullPointerExceptions. Instead of returning null, you can return None, and the caller of the function is forced to deal with the possibility that there might not be a value.

flatMap in Scala is used to flatten a nested collection. It first applies a function to all elements of a collection and then flattens the results. This is useful when you have a collection of collections and you want to create a single collection that contains all the elements.