sample code for list average tutorial

Author: pedrorijo91

scala-core-collections-modules/scala-core-collections-4/README.md

@@ -1,3 +1,4 @@
 ## Relevant Articles
 - [Using filter() and takeWhile() With Collections in Scala](https://www.baeldung.com/scala/filter-takewhile)
 - [Finding Elements in a List using takeWhile() and dropWhile() in Scala](https://www.baeldung.com/scala/list-find-takewhile-dropwhile)
+- [Calculate the Average of a List in Scala](https://www.baeldung.com/scala/calculate-the-average-of-a-list-in-scala)

scala-core-collections-modules/scala-core-collections-4/src/main/scala/com/baeldung/scala/listaverage/ListAverage.scala

@@ -0,0 +1,45 @@
+package com.baeldung.scala.listaverage
+
+object ListAverage {
+
+
+  def naive(lst: List[Int]): Int  = {
+    var total = 0
+    var nrElements = 0
+
+    for(elem <- lst) {
+      total += elem
+      nrElements += 1
+    }
+
+    total / nrElements
+  }
+
+
+  def averageDouble(lst: List[Int]): Double = {
+    var total = 0
+
+    // here we use double to ensure we dont round final number
+    var nrElements = 0.0
+
+    for (elem <- lst) {
+      total += elem
+      nrElements += 1
+    }
+
+    total / nrElements
+  }
+
+  def averageWithListMethods(lst: List[Int]): Int = {
+    lst.sum / lst.size
+  }
+
+  def averageWithListMethodsDouble(lst: List[Int]): Double = {
+    lst.sum / lst.size.toDouble
+  }
+
+  def averageWithFold(lst: List[Int]): Double = {
+    val (sum, size) = lst.foldLeft((0.0, 0))((pair, elem)=>(pair._1 + elem, pair._2 + 1))
+    sum / size
+  }
+}

scala-core-collections-modules/scala-core-collections-4/src/test/scala/com/baeldung/scala/listaverage/ListAverageUnitTest.scala

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+package com.baeldung.scala.listaverage
+
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class ListAverageUnitTest extends AnyFlatSpec with Matchers {
+  val lst = List(1,2,3,4,5)
+
+  "naive" should "return rounded average 2" in {
+    ListAverage.naive(lst) shouldBe 2
+  }
+
+  "naive with double" should "return average 2.5" in {
+    ListAverage.averageDouble(lst) shouldBe 2.5
+  }
+
+  "averageWithListMethods" should "return rounded average 2" in {
+    ListAverage.averageWithListMethods(lst) shouldBe 2
+  }
+
+  "averageWithListMethodsDouble" should "return average 2.5" in {
+    ListAverage.averageWithListMethodsDouble(lst) shouldBe 2.5
+  }
+
+  "averageWithFold" should "return average 2.5" in {
+    ListAverage.averageWithFold(lst) shouldBe 2.5
+  }
+
+}