map

How to create an empty Scala Map

If you need to create an empty Map in Scala, the following examples show how to create empty immutable and mutable maps.

An empty immutable Map

You can use these approaches to create an empty immutable Scala Map:

val a = Map[Int, String]()
val a = Map.empty[Int, String]

Here’s what they look like in the REPL:

Scala List class: methods, examples, and syntax

This page contains a large collection of examples of how to use the methods on the Scala List class.

The Scala List class as an immutable, linear, linked-list class. It’s very efficient when it makes sense for your algorithms to (a) prepend all new elements, (b) work with it in terms of its head and tail elements, and (c) use functional methods that traverse the list from beginning to end, such as filter, map, foldLeft, reduceLeft.

Scala Seq class: methods, examples, and syntax

This page contains a large collection of examples of how to use the methods on the Scala Seq class.

Important note about Seq, IndexedSeq, and LinearSeq

As an important note, I use Seq in the following examples to keep things simple, but in your code you should be more precise and use IndexedSeq or LinearSeq where appropriate. As the Seq class Scaladoc states:

Scala: A look at flatMap and map on Option

As a quick Scala tip, if you haven’t worked with the flatMap on an Option much, it can help to know that flatMap’s function should return an Option, which you can see in this REPL example:

scala> Some(1).flatMap{ i => Option(i) }
res0: Option[Int] = Some(1)

You can tell this by looking at the function signature in the scaladoc for the flatMap method on the Option class:

Scala Vector transformer methods (syntax, examples)

This page contains a large collection of examples of how to use Scala Vector class transformer methods.

Transformer methods

A transformer method is a method that constructs a new collection from an existing collection.