Steps

1. How to initialize a Sequence of donuts

The code below shows how to initialize a sequence of donut elements where each element in the sequence is of type String.

println("Step 1: How to initialize a Sequence of donuts")
val donuts: Seq[String] = Seq("Plain Donut", "Strawberry Donut", "Glazed Donut")
println(s"Elements of donuts = $donuts")

You should see the following output when you run your Scala application in IntelliJ:

Step 1: How to initialize a Sequence of donuts
Elements of donuts = List(Plain Donut, Strawberry Donut, Glazed Donut)

2. How to group elements in a sequence using the groupBy function

The code below shows how to use the groupBy method to group elements in the donut sequence by the first character for each donut.

println("\nStep 2: How to group elements in a sequence using the groupBy function")
val donutsGroup: Map[Char, Seq[String]] = donuts.groupBy(_.charAt(0))
println(s"Group elements in the donut sequence by the first letter of the donut name = $donutsGroup")

You should see the following output when you run your Scala application in IntelliJ:

Step 2: How to group elements in a sequence using the groupBy function
Group elements in the donut sequence by the first letter of the donut name = Map(S -> List(Strawberry Donut), G -> List(Glazed Donut), P -> List(Plain Donut))

NOTE:

• We end up with a Map where the letter S points to Strawberry Donut, letter G points to Glazed Donut and P points to Plain Donut.

3. How to create a case class to represent Donut objects

The code below shows how to use a Case Class to represent donut objects.

println("\nStep 3: How to create a case class to represent Donut objects")
case class Donut(name: String, price: Double)

4. How to create a Sequence of type Donut

The code below shows how to use the Donut case class from Step 3 and create a sequence of donut elements of type Donut.

println("\nStep 4: How to create a Sequence of type Donut")
val donuts2: Seq[Donut] = Seq(Donut("Plain Donut", 1.5), Donut("Strawberry Donut", 2.0), Donut("Glazed Donut", 2.5))
println(s"Elements of donuts2 = $donuts2")

You should see the following output when you run your Scala application in IntelliJ:

Step 4: How to create a Sequence of type Donut
Elements of donuts2 = List(Donut(Plain Donut,1.5), Donut(Strawberry Donut,2.0), Donut(Glazed Donut,2.5))

5. How to group case classes donut objects by the name property

The code below shows how to group the donut objects represented by case class Donut from Step 3 by their name property using the groupBy method.

println(s"\nStep 5: How to group case classes donut objects by the name property")
val donutsGroup2: Map[String, Seq[Donut]] = donuts2.groupBy(_.name)
println(s"Group element in the sequence of type Donut grouped by the donut name = $donutsGroup2")

You should see the following output when you run your Scala application in IntelliJ:

Step 5: How to group case classes donut objects by the name property
Group element in the sequence of type Donut grouped by the donut name = Map(Glazed Donut -> List(Donut(Glazed Donut,2.5)), Plain Donut -> List(Donut(Plain Donut,1.5)), Strawberry Donut -> List(Donut(Strawberry Donut,2.0)))