Merge pull request #1337 from yadavan88/filter-takeWhile

Code sample for filter and takeWhile method differences

Author: dominiqueplante

build.sbt

@@ -208,6 +208,13 @@ lazy val scala_core_collections_3 =
       libraryDependencies ++= scalaTestDeps
     )
 
+lazy val scala_core_collections_4 =
+  (project in file("scala-core-collections-modules/scala-core-collections-4"))
+    .settings(
+      scalaVersion := scala3Version,
+      libraryDependencies ++= scalaTestDeps
+    )
+
 lazy val scala_core_map =
   (project in file("scala-core-collections-modules/scala-core-map"))
     .settings(

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

@@ -0,0 +1,3 @@
+## Relevant Articles
+
+- 

scala-core-collections-modules/scala-core-collections-4/src/test/scala/com/baeldung/scala/filtertakewhile/FilterAndTakeWhileUnitTest.scala

@@ -0,0 +1,46 @@
+package com.baeldung.scala.filtertakewhile
+
+import org.scalatest.matchers.should.Matchers
+import org.scalatest.wordspec.AnyWordSpec
+
+import java.time.{LocalDate, LocalDateTime}
+import scala.concurrent.{Await, Future, TimeoutException}
+import scala.concurrent.ExecutionContext.Implicits.global
+import scala.concurrent.duration.*
+
+class FilterAndTakeWhileUnitTest extends AnyWordSpec with Matchers {
+
+  "filter" should {
+    "filter all elements matching the condition" in {
+      val numbers = List(1, 2, 3, 4, 5, 6)
+      val oddNumbers = numbers.filter(_ % 2 != 0)
+      oddNumbers shouldBe List(1, 3, 5)
+    }
+
+    "not complete the execution due to infinite collection" ignore {
+      val infiniteNumbers = LazyList.from(1)
+      val lessThan100 =
+        infiniteNumbers.filter(_ < 100).toList // never completes
+    }
+  }
+
+  "takeWhile" should {
+    "select elements until the predicate fails" in {
+      val numbers = List(1, 2, 3, 4, 5, 6)
+      val numbersBeforeFirstEven = numbers.takeWhile(_ % 2 != 0)
+      numbersBeforeFirstEven shouldBe List(1)
+    }
+
+    "select different list of elements if the list item changes" in {
+      val numbers = List(1, 3, 4, 5, 6)
+      val numbersBeforeFirstEven = numbers.takeWhile(_ % 2 != 0)
+      numbersBeforeFirstEven shouldBe List(1, 3)
+    }
+
+    "successfully get result from an infinite collection" in {
+      val infiniteNumbers = LazyList.from(1)
+      val first100 = infiniteNumbers.takeWhile(_ < 100).toList
+      first100 shouldBe (1 to 99).toList
+    }
+  }
+}