add package demo

README.md

@@ -528,6 +528,8 @@
 	- [OOP hw 1](./src/main/scala/ScalaHomework) 
 
 10. Scala advance
+	- Package object
+		- [demo](./src/main/scala/ScalaAdvance/PackageDemo)
 	- Parallel
 		- [parallel_Demo_1](./src/main/scala/ScalaAdvance/parallel_Demo_1.scala)
 		- Scala offers the `parallel` collections that can be processed in `parallel` with machines have multi-core CPU

src/main/scala/ScalaAdvance/PackageDemo/demo1.scala

@@ -0,0 +1,27 @@
+package ScalaAdvance.PackageDemo
+
+/**
+ *  Scala Package object demo 1
+ *
+ *  ref :  https://github.com/yennanliu/til#20211215
+ *
+ */
+
+import ScalaAdvance.PackageDemo.service.myService._
+
+object demo1 extends App {
+
+  // demo 1 : package attr, method
+  println("planted " + planted)
+  printDefault("123")
+
+  println("=====================")
+
+  // demo 2 : package constructor's attr, method
+  val myService1  = new myService("m")
+  println("myService1 = " + myService1.toString)
+  myService1.print("hiiii")
+
+  val res1 = myService1.dummyHttpCall("hitttt")
+  println("res1 = " + res1)
+}

src/main/scala/ScalaAdvance/PackageDemo/service/myService.scala

@@ -0,0 +1,33 @@
+package ScalaAdvance.PackageDemo.service
+
+// https://docs.scala-lang.org/zh-cn/tour/package-objects.html
+
+package object myService {
+
+  // attr
+  case class Fruit(name: String, color: String)
+  object Apple extends Fruit("Apple", "green")
+  object Plum extends Fruit("Plum", "blue")
+  object Banana extends Fruit("Banana", "yellow")
+
+  val planted = List(Apple, Plum, Banana)
+
+  // constructor
+  class myService(host:String){
+
+    // method
+    def print(input:String):Unit = {
+      println(">>>> input = " + input)
+    }
+
+    def dummyHttpCall(httpRequest:String):String = {
+      s"this is my request : $httpRequest"
+    }
+  }
+
+  // method
+  def printDefault(input:String):Unit = {
+    println(">>>> printDefault = " + input)
+  }
+
+}

src/main/scala/ScalaDev/test1.scala

@@ -0,0 +1,13 @@
+package ScalaDev
+
+object test1 extends App {
+
+  val x = List(1,2,3)
+
+  val x_1 = x.map( (i:Int) => i+1)
+
+  println (x_1.toString)
+
+  List((1,2),(2,3),(3,4),(2,5)).map(x => x.toString)
+}
+