example for some sink operators #25468

Examples for takeLast, last and lastOption operators

akka-stream-tests/src/test/scala/akka/stream/scaladsl/TakeLastSinkSpec.scala

@@ -25,6 +25,36 @@ class TakeLastSinkSpec extends StreamSpec {
       result should be(Seq(4, 5, 6))
     }
 
+    "return top three student based on GPA correctly" in {
+      implicit val ex = system.dispatcher
+      //#takeLast-operator-example
+      case class Student(name: String, gpa: Double)
+
+      val students = List(Student("Alison", 4.7), Student("Adrian", 3.1), Student("Alexis", 4),
+        Student("Benita", 2.1), Student("Kendra", 4.2), Student("Jerrie", 4.3)).sortBy(_.gpa)
+
+      val sourceOfStudents = Source(students)
+
+      val result: Future[Seq[Student]] = sourceOfStudents.runWith(Sink.takeLast(3))
+
+      result.foreach { topThree ⇒
+        println("#### Top students ####")
+        topThree.reverse foreach { s ⇒
+          println(s"Name: ${s.name}, GPA: ${s.gpa}")
+        }
+      }
+      /*
+          #### Top students ####
+          Name: Alison, GPA: 4.7
+          Name: Jerrie, GPA: 4.3
+          Name: Kendra, GPA: 4.2
+      */
+
+      //#takeLast-operator-example
+
+      result.futureValue shouldEqual students.takeRight(3)
+    }
+
     "return the number of elements taken when the stream completes" in {
       val input = 1 to 4
       val future: Future[immutable.Seq[Int]] = Source(input).runWith(Sink.takeLast(5))