详解Kotlin中的变量和方法

var name: String = "jason"
name = "jame"

val max = 10

object Config {
  const val TAG = "config"
}

class Config {
  companion object {
  const val TAG = "config"
}
}

fun log(msg: String): Unit {
  println(msg)
}

fun square(x: Int) = x * x

fun main(args: ArrayList<String>) {
  //
}

class Hello() {
  //
}

fun divide(divisor: BigDecimal, scale: Int = 0): BigDecimal

class Student2(val name: String, val registered: Boolean = false, credits: Int = 0)

fun deleteFiles(filePattern: String, recursive: Boolean, ignoreCase: Boolean, 
    deleteDirectories: Boolean): Unit
{
  // do something
}

deleteFiles("*.jpg", true, true, false)

deleteFiles("*.jpg", recursive = true, ignoreCase = true, deleteDirectories = false)

fun prints(vararg strings: String) {
  for (string in strings)
  println(string)
}

prints("a", "b", "c")

val strings = arrayOf("a", "b", "c", "d", "e")
prints(*strings)

fun roots(k: Int): Pair<Double, Double> {
  require(k >= 0)
  val root = Math.sqrt(k.toDouble())
  return Pair(root, -root)
}

val (pos, neg) = roots(16)

tailrec fun findFixPoint(x: Double = 1.0): Double = if (x == Math.cos(x)) x 
    else findFixPoint(Math.cos(x))

val printMessage = { message: String -> println(message) }

printMessage("hello")
printMessage("world")