Classes and Objects code seperated

Companion class Example added

Author: CodeLab20

4.Classes-Objects/Box.scala renamed to 4.Classes/Box.scala

@@ -0,0 +1,25 @@
+import java.time._
+
+class Employee protected(val firstName:String, val lastName: String, val title:String, val hireDate:LocalDate)
+
+object Employee
+{
+    def createEmployee(firstName:String, lastName:String, title:String) = new Employee(firstName, lastName, title, LocalDate.now)
+    
+    def createEmployee(firstName:String, lastName:String, title:String, hireDate:LocalDate) = new Employee(firstName, lastName, title, hireDate)
+}
+
+object EmployeeDesignRunner extends App
+{
+    val e1 = Employee.createEmployee("Bruce", "Wayne", "BatMan")
+    println(e1.hireDate)
+}
+
+/**
+    Sample Output
+    
+> scalac EmployeeDesign.scala
+
+> scala EmployeeDesignRunner
+    2017-04-30
+**/

4.Classes-Objects/BoxScript.scala renamed to 4.Classes/BoxScript.scala

@@ -0,0 +1,17 @@
+object MainRunner
+{
+    def main(args:Array[String]):Unit = println("Hello from Scala Main Method!!!")
+}
+
+/**
+    Sample Output
+> scala MainRunner.scala
+Hello from Scala Main Method!!!
+
+//compiling scala file
+scalac MainRunner.scala
+
+//Running scala class using java
+> java -cp .;C:\scala\lib\scala-library.jar MainRunner
+Hello from Scala Main Method!!!
+**/

4.Classes-Objects/CheckSummer.scala renamed to 4.Classes/CheckSummer.scala

@@ -0,0 +1,16 @@
+/**
+    If object extends from App, then defining main method is not required.
+*/
+object MainRunnerApp extends App
+{
+    println("Hello from Scala App!!!")
+}
+
+/**
+Sample output
+
+> scalac MainRunnerApp.scala
+
+> scala MainRunnerApp
+Hellow from Scala App!!!
+**/

4.Classes-Objects/ChecksumAccumulator.scala renamed to 4.Classes/ChecksumAccumulator.scala

@@ -0,0 +1,37 @@
+//Objects are like utility classes in java. methods in objects can be considered as static methods in jav
+//all objects in scala are singleton.
+/***
+    Objects in scala can be used for:
+    1. Singleton 
+    2. Factory pattern
+    3. Pattern matching login
+    4. Utility method which does not require instance or state
+    5. Default values
+    6. Main method
+**/
+
+object MyObject
+{
+    def add(x:Int, y:Int)= x+y    
+}
+
+println("10 + 20 = " + MyObject.add(10,20))
+
+class Employee(val firstName:String, val lastName:String, val title:String)
+
+//any object can extend from a class
+object NewEmployee extends Employee("James", "Bond", "Spy")
+
+println("FirstName:" + NewEmployee.firstName)
+println("LastName:" + NewEmployee.lastName)
+println("Title:" + NewEmployee.title)
+
+
+/**
+Sample Output
+
+10 + 20 = 30
+FirstName:James
+LastName:Bond
+Title:Spy
+**/

4.Classes-Objects/Couple.scala renamed to 4.Classes/Couple.scala

@@ -0,0 +1,53 @@
+/**
+    1.Class SecretAgent and object SecretAgent are called as companion object.
+    2.For companion classes, create a class and an object with same name.
+    3.Both class and object must present in same file.
+    4.Companion object can't have main method
+    5.Companion object can have access to private members in Companion class
+    6.Companion classes have access to private members in Companion object.
+*/
+
+class SecretAgent(val name:String)
+{
+    def shoot(n:Int)
+    {
+        import SecretAgent._        //This means every method inside SecretAgent companion object is imported
+        decrementBullets(n)
+    }
+}
+
+object SecretAgent
+{
+    private var bullets:Int = 3000
+    
+    private def decrementBullets(count:Int)=
+    {
+        if((bullets - count) <= 0 ) bullets = 0
+        else
+            bullets = bullets - count
+    }
+    
+    def getBullets:Int = bullets
+}
+
+object SecretAgentRunner extends App
+{
+    val bond = new SecretAgent("James Bond")
+    val ethan = new SecretAgent("Ethan Hunt")
+    val jason = new SecretAgent("Jason Bourne")
+    
+    bond.shoot(800)
+    ethan.shoot(400)
+    jason.shoot(300)
+    
+    println("Bullets Left are :" + SecretAgent.getBullets)
+}
+
+/**
+    Sample Output
+> scalac SecretAgent.scala
+
+> scala SecretAgentRunner
+Bullets Left are :1500
+
+**/

4.Classes-Objects/CoupleScript.scala renamed to 4.Classes/CoupleScript.scala

@@ -0,0 +1,26 @@
+class Person(val name:String, private val superHeroName:String)
+
+object Person
+{
+    def showSuperHeroName(p:Person) = p.superHeroName   //Companion object can have access to private members in Companion class
+}
+
+object SuperHeroRunner extends App
+{
+    val p1 = new Person("Peter Parker", "Spiderman")
+    println(Person.showSuperHeroName(p1))
+}
+
+/**
+    Sample output
+    
+    > scala SuperHeroes.scala
+
+> scalac SuperHeroes.scala
+
+> scala SuperHeroes
+
+> scala SuperHeroRunner
+Spiderman
+
+**/