Initial Commit for Kotlin Demo

Class/src/sample.kts

@@ -0,0 +1,23 @@
+class Car {
+  var yearOfRegistration = 2010
+//    set(value) {
+//      if(value > 2017)
+//        throw RuntimeException("can't register into the future")
+//      field = value
+//    }
+
+  val yearsSinceRegistration
+    get() = 2017 - yearOfRegistration
+}
+
+val car = Car()
+
+println(car.yearOfRegistration)
+
+car.yearOfRegistration = 2014
+
+println(car.yearOfRegistration)
+
+println(car.yearsSinceRegistration)
+
+//car.yearOfRegistration = 2019

ComplileAndRun/src/sample.kt

@@ -0,0 +1,13 @@
+fun main(args: Array<String>) {
+  println("Hello ${args[0]}")
+}
+
+/*
+kotlinc sample.kt -include-runtime -d sample.jar
+java -classpath sample.jar SampleKt World
+
+or
+
+kotlinc sample.kt -d classes
+kotlin -classpath classes SampleKt World
+*/

DSL/src/sample.kts

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+class Robot {
+  val left = "Left"
+  val right = "Right"
+  val fast = "Fast"
+
+  infix fun turns(direction: String) {
+    println("turns $direction")
+  }
+
+  infix fun runs(speed: String) {
+    println("runs $speed")
+  }
+}
+
+fun operate(func: Robot.(theRobot: Robot) -> Unit) {
+  val robot = Robot()
+  robot.func(robot)
+}
+
+operate {        
+  it turns left
+  it turns right
+  it runs fast
+}

DataClasses/src/sample.kts

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+data class Person(val first: String, val last: String)
+
+val peter = Person("Peter", "Parker")
+
+println(peter)
+println(peter.first)
+println(peter.component1())            

DefaultArgs/src/sample.kts

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+fun greet(name: String, msg: String = "Hi ${name.length}") = "$msg $name"
+
+println(greet("Tom", "Hello"))
+println(greet("Jerry"))
+println(greet(msg = "Howdy", name = "Spike"))
+println(greet("Tyke", msg = "Yo"))

ExtentionMethod/src/sample.kts

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+fun String.shout() = toUpperCase()
+
+println("hello".shout())

For/src/sample.kts

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+for(x in 1..10) {
+  println(x)
+}
+println("------")
+
+for(x in 1 until 10) {
+  println(x)
+}
+println("------")
+
+for(x in 1..10 step 2) {
+  println(x)
+}
+println("------")
+
+for(x in 10 downTo 1) {
+  println(x)
+}
+println("------")
+
+for(x in 10 downTo 1 step 2) {
+  println(x)
+}
+println("------")
+
+val names = listOf("Jack", "Jill", "Tom", "Kate")
+
+for(name in names) {
+  println(name)
+}
+println("------")
+
+for(index in names.indices) {
+  println("$index -- ${names.get(index)}")
+}

Function/src/sample.kts

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+fun greet(name: String) = "Hello $name"
+
+println(greet("Bob"))
+
+fun greet2(name: String) : String {
+  return "Howdy $name"
+}
+
+println(greet2("Jane"))
+
+fun printGreet(name: String) {
+  println("Hi $name")
+}
+
+printGreet("Mike")

FunctionalType/src/sample.kts

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+val double = { e: Int -> e * 2 }
+println(double(2))
+
+println("----")
+
+listOf(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+  .filter { it % 2 == 0}
+  .map(double)
+  .forEach { println(it) }

Infix/src/sample.kts

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+class Pizza {
+  infix fun spread(item: String) {
+    println("spreading $item")
+  }
+}
+
+val pizza = Pizza()
+
+pizza.spread("Sauce")
+pizza.spread("Cheese")
+
+pizza spread "Sauce"
+pizza spread "Cheese"

Inheritance/src/sample.kts

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+open class Person(val first: String, val last: String) {
+  open fun work() { println("working...") }
+
+  override fun toString() = "$first $last"
+}
+
+class CoolPerson(first : String, last: String) : Person(first, last) {
+  var coolnessIndex = 5
+
+  constructor(first: String, last: String, index: Int) : this(first, last) {
+    coolnessIndex = index
+  }                                              
+
+  override fun work() {
+    println("overridden work")
+    super.work()
+  }
+
+  override fun toString() = "${super.toString()} ${coolnessIndex}"
+}
+
+val coolPerson = CoolPerson("Alan", "Turing", 10)
+println(coolPerson)
+coolPerson.work()

Lazy/src/sample.kts

@@ -0,0 +1,22 @@
+fun compute(n: Int) : Int {
+  println("called...")
+  return n
+}
+
+val x = 4
+
+if(x > 4 && compute(4) > 2)
+  println("result")
+
+println("----")  
+
+val temp = compute(4)
+if(x > 4 && temp > 2)
+  println("result")
+
+println("----")  
+
+val temp2 by lazy { compute(4) }
+if(x > 4 && temp2 > 2)
+  println("result")
+

MultilineString/src/sample.kts

@@ -0,0 +1,13 @@
+val name = "Job"
+
+val memo = """
+  |This message was created by $name and
+  |is being delivered
+  |securty to...
+"""
+
+println(memo)
+
+println(memo.trimMargin())
+
+println(memo.trimMargin("|")) //replace | with ~, for example.

NullTypeParam/src/sample.kts

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+fun receive1(name: String?) {
+  //println(name.length) //ERROR
+
+  if(name != null)
+    println("Size is ${name.length}") //auto casting
+  else
+    println("Size is 0")
+}
+
+fun receive2(name: String?) {
+  println("Size is ${name?.length ?: 0}")
+}
+
+receive1("Joe")
+receive1(null)
+
+receive2("Joe")
+receive2(null)

Repel/src/readme.txt

@@ -0,0 +1,7 @@
+On the command prompt type kotlinc, which also works as REPL
+
+>kotlinc
+Welcome to Kotlin ...
+Type :help for help, :quit for quit
+=>>> println("hi")
+>hi

ReturnNull/src/sample.kts

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+fun nickName(name: String) : String? {
+  if(name == "Robert")
+    return "Bob";
+  return null;
+}
+
+println(nickName("Robert"))
+println(nickName("Venkat"))

RunAsScript/src/sample.kt

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+//println("Hello World")
+
+//kotlinc -script sample.kts World

Statements/src/sample.kts

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+val age = 17
+
+val canVote = if(age > 17) "Please vote" else "Not so fast, kid"
+println(canVote)
+

StaticMethodAndCompanion/src/sample.kts

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+object Util {
+  fun getNumberOfCores() = Runtime.getRuntime().availableProcessors()
+} 
+
+class Car {                         
+  companion object { //May optionally take a name after object, for example CarKind
+    fun kind() = "Electric"
+  }         
+
+  fun drive() { println("driving") }
+}
+
+println(Util.getNumberOfCores())
+
+val car = Car()
+car.drive()
+
+println(Car.kind())
+
+val companion = Car.Companion //If CarKind is used above, then Car.CarKind
+println(companion)

String/src/sample.kts

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+val name = "Bob";
+
+println("Hello $name, how are you?")

ValAndVar/src/sample.kts

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+val number1 = 4
+println(number1)
+
+//number1 = 4 //ERROR
+
+var number2 = 4
+println(number2)
+
+number2 = 5
+println(number2)

VarArgs/src/sample.kts

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+fun max(vararg numbers: Int) = numbers.reduce { max, e -> if(max < e) e else max }
+
+println(max(1, 2))
+println(max(7, 3, 11))
+
+val values = intArrayOf(1, 22, 4)
+println(max(4, 5, *values, 8))

When/src/sample.kts

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+fun process(input: Any) { 
+  when(input) {
+    1 -> println("That's one")
+    7, 8 -> println("7 or 8")
+    in 13..19 -> println("teen")
+    is String -> println("got a String of length ${input.length}")
+    else -> println("no clue")
+  }
+}
+
+process(1)              
+process(7)
+process(8)              
+process(16)             
+process("hello")  //notice automatic casting
+process(StringBuilder())