初心者向けScala文法の資料です (@Scala関西Summit 2017)

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8. object Main {
def main(args: Array[String]): Unit = {
val message1 = "Hello"
var message2 = "World"
message2 += "!"
println(message1 + " " + message2)
}
}
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9. def main(args: Array[String]): Unit = {
val message1 = "Hello"
var message2 = "World"
message2 += "!"
println(message1 + " " + message2)
}
[]
Unit
void
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10. {
val message1 = "Hello"
var message2 = "World"
message2 += "!"
println(message1 + " " + message2)
}
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11. def twice(x: Int): Int = {
x * 2
}
def twice(x: Int): Int = x * 2
{}
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12. val result = {
val x = 1 + 2
if (x < 0) x else x * 2
}
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13. val result = {
val x = 1 + 2
if (x < 0) x else x * 2
}
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14. for {i <- 1 to 3} {
println(i)
}
for {i <- 1 to 3} println(i)
val results = for {i <- 1 to 3} i
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15. val results1 = for {i <- 1 to 3} yield i
val results2 = for {
i <- 1 to 5 by 2
j <- 2 to 1 by -1
} yield {
val x = i * j
x + 1
}
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16. val n = 2
val result = n match {
case 1 =>
"1"
case 2 | 3 =>
"2 or 3"
case x if x % 2 == 0 =>
" " + x.toString
case x =>
s" ${x}"
}
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17. val n = 5
val result = n match {
case 1 =>
"1"
case 2 | 3 =>
"2 or 3"
case x if x % 2 == 0 =>
" " + x.toString
case x =>
s" ${x}"
}
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18. class Triangle(edges: Array[Int]) {
val area = ??? //
def printFigure(): Unit = println(" ")
}
val triangle = new Triangle(Array(3, 4, 5))
println(triangle.area)
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19. abstract class Polygon(edges: Array[Int]) {
val n = edges.size
val area: Double
def printFigure(): Unit
}
class Triangle(edges: Array[Int]) extends Polygon(edges) {
val area = ??? //
def printFigure(): Unit = println(" ")
}
val triangle = new Triangle(Array(3, 4, 5))
println(triangle.area)
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20. abstract class Polygon private(edges: Array[Int]) {
val n = edges.size
val area: Double
def printFigure(): Unit
}
object Polygon {
def fromEdges(edges: Array[Int]): Polygon =
edges.size match {
case 3 => new Triangle(edges)
case 4 => new Square(edges)
case n => ???
}
}
Polygon.fromEdges(Array(3, 4, 5))
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21. import java.util.Date
trait Tag {
val createdDate: Date
}
trait Color {
val rgb: RGB
}
class TaggedGreenTriangle
extends Triangle with Tag with Color {
val rbg = new RGB(0, 255, 0)
val createdDate = new Date
}
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22. val list1 = (1 to 3).toList
val list2 = List(1, 2, 3)
val array = Array(1, 2, 3)
val odds1 = list1.filter(x => x % 2 == 1)
val odds2 = array.filter(x => x % 2 == 1)
val sum = list1.sum
val twice = list1.map(x => x * 2)
val sorted = list1.sorted
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23. val list = (1 to 3).toList
val odds1 = list.filter(x => x % 2 == 1)
val selectOdd: Int => Boolean = x => x % 2 == 1
val odds2 = list.filter(selectOdd)
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24. def getData(q: Query): Option[String] = ???
getData(q) match {
case Some(str) => println(str)
case None => println(" ")
}
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25. def getNullableString(): String = ??? //
val stringOpt = Option(getNullableString())
stringOpt match {
case Some(str) => println(str)
case None => println("null ")
}
def throwableMethod(): Int = ??? //
val result = try {
throwableMethod()
} catch {
case ex: Throwable => 0
}
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26. val list = (1 to 3).toList
list.foreach(x => println(x))
def getNullableString(): String = ??? //
val stringOpt = Option(getNullableString())
stringOpt.foreach(str => println(str))
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28. val x1 = 1 + 2
val x2 = 1.+(2)
implicit class MyInt(val x: Int) extends AnyVal {
def add(another: Int): Int = x + another
}
val y1 = 1.add(2)
val y2 = 1 add 2
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29. class Cat(cry: String) {
def apply(postfix: String): Unit =
println(cry + postfix)
}
object Cat {
def apply(cry: String): Cat = new Cat(cry)
}
val cat1 = new Cat(" ")
val cat2 = Cat(" ")
val cat3 = Cat.apply(" ")
cat1("!")
cat1.apply("!")
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30. class Cat(cry: String)
val cat = new Cat(" ")
// cry private
class Cat(val cry: String)
val cat = new Cat(" ")
// val
println(cat.cry)
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31. case class Cat(cry: String)
val cat1 = new Cat(" ")
val cat2 = Cat(" ")
val cat3 = Cat.apply(" ")
println(cat1.cry)
println(cat1.toString)
getData(q) match {
case Some(str) => println(str)
case None => println(" ")
}
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