Chapter3 ごちゃまぜ。

Shape.scala

package chapter3

/**
  * Created by hoshi on 1/12/16.
  */
class Shape {
  def area:Double = 0.0
}

class Rectangle(val width:Double, val height:Double) extends Shape {
  override def area:Double = width*height
}
class Circle(val radius:Double) extends Shape {
  override def area:Double = math.Pi * radius * radius
}

object Chapter3 {
  def draw(s:Shape): Unit = {
    println(s.getClass + ":" + s.area)
  }

  def main(args: Array[String]): Unit = {
    println("Chapter3")

    draw(new Circle(3))
    draw(new Rectangle(2,3))
  }
}

----

package chapter3

/**
  * Created by hoshi on 1/12/16.
  */
class Book(val title:String, var author:String, private var code:String = "0000", hidden:String = "default") {
  def printCode {println(code)}
  def printValues(b: Book) {
    println(b.code) // 'private var' can access in the same class
    //println(b.hidden) // Parameter without val/var cannot access
  }
  def printHidden {println(hidden)}
  def printAll {
    println(s"$title, $author, $code, $hidden")
  }
}

object Main {
  def main(args: Array[String]) {
    val book = new Book("Scala", "hoge", "0001", "aaa")
    // book.title = "piyo" // no setter
    book.author = "piyo"
    // book.code //private
    book.printCode
    book.printValues(book)

    book.printValues(new Book("test", "test2", "0002", "bbb"))

    val book2 = new Book("hoge", "0002", "aaa")
    book2.printAll
    val book3 = new Book("hoge", "0003")
    book3.printAll
    val book4 = new Book("hoge", "0004", hidden="ABC") // you can choose to provide named parameters
    book4.printAll
  }
}

----

package chapter3

/**
  * Created by hoshi on 1/12/16.
  */
class AuxiliaryBook(var title:String, var ISBN: Int) {
  def this(title:String) {
    this(title, 2222)
  }

  def this() {
    this("Begging Erlang")
  }
  override def toString = s"$title ISBN- $ISBN"

}

object AuxiliaryMain {
  def main(args: Array[String]): Unit = {
    println(new AuxiliaryBook)
    println(new AuxiliaryBook("Clojure"))
    println(new AuxiliaryBook("Scala", 3333))
  }
}

----

package chapter3

import java.io.BufferedReader

/**
  * Created by hoshi on 1/12/16.
  */
class Methods {
  def mymethod() = "Moof"
  def foo(a: Int):String = a.toString
  def f2(a: Int, b:Boolean):String = if (b) a.toString else "false"
}

object MethodsMain {
  def list[T](p:T):List[T] = p :: Nil
  def largest(as: Int*): Int = as.max
  def mkString[T](as: T*):String = as.foldLeft("")(_ + _.toString)
  // The type must be Number or a subclass of Number
  def sum[T <:Number](as:T*):Double = as.foldLeft(0d)(_ + _.doubleValue())

  def readLines(br: BufferedReader) = {
    var ret: List[String] = Nil

    def readAll():Unit = br.readLine match {
      case null =>
      case s => ret ::= s; readAll()
    }
    readAll()
    ret.reverse
  }

  def main(args: Array[String]) {
    val m = new Methods
    println(m.mymethod())
    println(m.foo(5))
    println(m.f2(1,true))
    println(m.f2(2,false))

    println(list(1))
    println(list("test"))
    println(largest(1, 2, 3, 4, 5, 4, 3))
    println(mkString("aa", "b", "ccc"))
  }
}

----

package chapter3

/**
  * Created by hoshi on 1/12/16.
  */
abstract class Base {
  def thing: String
}

----

package chapter3

/**
  * Created by hoshi on 1/12/16.
  */
class One extends Base {
  def thing = "Moof"
}

class Two extends One {
  override val thing = (new java.util.Date).toString
}

class Three extends One {
  override lazy val thing = super.thing + (new java.util.Date).toString
}

object OneMain {
  def main(args: Array[String]) {
    val one = new One
    println(one.thing)

    val two = new Two
    println(two.thing)

    val three = new Three
    println(three.thing)
  }
}