Steps

1. How to initialize a TreeMap with 3 elements using Tuples key and value

The code below shows how to initialize a TreeMap with 3 elements using Tuples key and value.

import scala.collection.immutable.TreeMap
println("Step 1: How to initialize a TreeMap with 3 elements using Tuples key and value")
val treeMap1: TreeMap[String, String] = TreeMap(("PD","Plain Donut"),("SD","Strawberry Donut"),("CD","Chocolate Donut"))
println(s"Elements of treeMap1 = $treeMap1")

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

Step 1: How to initialize a TreeMap with 3 elements using Tuples key and value
Elements of treeMap1 = Map(CD -> Chocolate Donut, PD -> Plain Donut, SD -> Strawberry Donut)

NOTE:

• The TreeMap is sorted by default using the natural order the its key.
• In the above example, key CD is printed first followed by PD and then SD.

2. How to initialize TreeMap using key -> value notation

The code below shows how to initialize TreeMap using key -> value notation.

println("\nStep 2: How to initialize TreeMap using key -> value notation")
val treeMap2: TreeMap[String, String] = TreeMap("VD"-> "Vanilla Donut", "GD" -> "Glazed Donut")
println(s"Elements of treeMap2 = $treeMap2")

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

Step 2: How to initialize ListMap using key -> value notation
Elements of treeMap2 = Map(GD -> Glazed Donut, VD -> Vanilla Donut)

3. How to access elements of TreeMap by specific key

The code below shows how to access elements of TreeMap by specific key.

println("\nStep 3: How to access elements of TreeMap by specific key")
println(s"Element by key VD = ${treeMap2("VD")}")
println(s"Element by key GD = ${treeMap2("GD")}")

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

Step 3: How to access elements of TreeMap by specific key
Element by key VD = Vanilla Donut
Element by key GD = Glazed Donut

4. How to add elements to TreeMap using +

The code below shows how to add elements to TreeMap using +

println("\nStep 4: How to add elements to TreeMap using +")
val treeMap3: TreeMap[String, String] = treeMap1 + ("KD" -> "Krispy Kreme Donut")
println(s"Elements in treeMap3 = $treeMap3")

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

Step 4: How to add elements using +
Element in treeMap3 = Map(CD -> Chocolate Donut, KD -> Krispy Kreme Donut, PD -> Plain Donut, SD -> Strawberry Donut)

5. How to add two TreeMaps together using ++

The code below shows how to add two TreeMaps together using ++

println("\nStep 5: How to add two TreeMaps together using ++")
val treeMap4: TreeMap[String, String] = treeMap1 ++ treeMap2
println(s"Elements in treeMap4 = $treeMap4")

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

Step 5: How to add two TreeMaps together using ++
Elements in treeMap4 = Map(CD -> Chocolate Donut, GD -> Glazed Donut, PD -> Plain Donut, SD -> Strawberry Donut, VD -> Vanilla Donut)

6. How to remove key and its value from TreeMap using -

The code below shows how to remove key and its value from TreeMap using -

println("\nStep 6: How to remove key and its value from TreeMap using -")
val treeMap5: TreeMap[String, String] = treeMap4 - ("CD")
println(s"TreeMap without the key CD and its value = $treeMap5")

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

Step 6: How to remove key and its value from TreeMap using -
TreeMap without the key CD and its value = Map(GD -> Glazed Donut, PD -> Plain Donut, SD -> Strawberry Donut, VD -> Vanilla Donut)

7. How to change ordering of TreeMap to descending alphabet

The code below shows how to change ordering of TreeMap to descending alphabet.

println("\nStep 7: How to change ordering of TreeMap to descending alphabet")
object AlphabetOrdering extends Ordering[String] {
 def compare(key1:String, key2:String) = key2.compareTo(key1)
}
val treeMap6: TreeMap[String, String] = TreeMap(("PD","Plain Donut"),("SD","Strawberry Donut"),("CD","Chocolate Donut"))(AlphabetOrdering)
println(s"Elements of treeMap6 in descending order = $treeMap6")

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

Step 7: How to change ordering of TreeMap to descending alphabet
Elements of treeMap6 = Map(SD -> Strawberry Donut, PD -> Plain Donut, CD -> Chocolate Donut)

8. How to initialize an empty TreeMap

The code below shows how to initialize an empty TreeMap.

println("\nStep 8: How to initialize an empty TreeMap")
val emptyTreeMap: TreeMap[String,String] = TreeMap.empty[String,String]
println(s"Empty TreeMap = $emptyTreeMap")

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

Step 8: How to initialize an empty TreeMap
Empty TreeMap = Map()