Senior Software Developer Alejandro Lujan discusses the collections API in Scala, and provides some insight into what it can do with with some examples.

1. Scala:
collec)ons

2. The
collec)ons
API
• Very
rich
library
for
manipula)ng
collec)ons
of
objects
• Great
examples
of
higher
order
func)ons
• The
usual
suspects:
Lists,
Sets,
Hash
Maps.
• But
also:
Streams,
Buffers,
Arrays,
Trees

3. Let's
take
this
model
case class Category(
name: String,
parent: Option[Category])
case class Product(
name: String,
description: String,
category: Category)

4. Given
a
list
of
products
• Sort
them
by
name
• Get
their
names
in
uppercase
• Get
the
set
of
categories
(no
repeats)
• Group
them
by
the
ini)al
of
their
names
• Return
a
tuple
with
the
product
and
category
names

5. Sor)ng
case class Product(
name: String,
description: String,
category: Category)
val products = List( ... ) // List of products
// Sort by name
products.sortBy(_.name)

6. Mapping
// Get their names in uppercase
val names: List[String] =
products.map(_.name.toUpperCase)

7. Extrac)ng
// Get category name set
val catNames : Set[String] =
products.map(_.category.name).toSet

8. Grouping
// Group by the initial of their names
val grouped : Map[Char, List[Product]] =
products.groupBy(_.name.head)

9. More
Mapping
// Create tuples of product and category
names
val pairs : Tuple2[String,String] =
for {
product <- products
category = product.category
} yield (product.name, category.name)