println("itemB:$itemB")

//字符串模板
var userInfo = "name:${user.name}, age:$age"

//三引號(hào)的形式用來(lái)輸入多行文本
val str = """ 
  one
  two
    """
//等價(jià)于     
val str = "one\ntwo"

//在變量類(lèi)型后面加上問(wèn)號(hào)，代表該變量是可空變量 
var name: String? = "zhangsan" 

/**
 * 如果str不能轉(zhuǎn)為Int類(lèi)型，則返回null
 */
fun parseInt(str: String): Int? { 
 // (代碼略)
}

val num: Int = 128;
val a:Int? = num
val b:Int? = num
println(a == b)
print(a === b)

if (i in 1..10) { // 等同于 1 <= i && i <= 10
  println(i)
}
//使用until函數(shù),創(chuàng)建一個(gè)不包括其結(jié)束元素的區(qū)間
for (i in 1 until 10) {  // i in [1, 10) 排除了 10
   println(i)
}

for (i in 1..4) print(i) // 輸出“1234”

for (i in 4..1) print(i) // 什么都不輸出

for (i in 1..4 step 2) print(i) // 輸出“13”

for (i in 4 downTo 1 step 2) print(i) // 輸出“42”

val book = Book(1, "英語(yǔ)")
val (id, _) = book

//得到類(lèi)的Class對(duì)象
startActivity(Intent(this@KotlinActivity, MainActivity::class.java))

//內(nèi)聯(lián)函數(shù)和reified后續(xù)介紹
inline fun <reified T> Gson.fromJson(json:String):T
{
  return fromJson(json, T::class.java)
}

var setBook = setOf<String>("hello", "hi", "你好")
//  setBook.forEach { print(it)}
  setBook.forEach(::print)

class User {
  inner class State{
    fun getUser(): User{
      //返回User
      return this@User
    }
    fun getState(): State{
      //返回State
      return this@State
    }
  }
}

loop@ for (itemA in arraysA) {
   var i : Int = 0
   for (itemB in arraysB) {
     i++
     if (itemB > 2) {
       break@loop
     }

     println("itemB:$itemB")
   }

}

fun fun_run(){
  run {
    println("lambda")
  }
  var i: Int = run {
    return@run 1
  }
  println("$i")
  //匿名函數(shù)可以通過(guò)自定義標(biāo)簽進(jìn)行跳轉(zhuǎn)和返回
  i = run (outer@{
    return@outer 2
  })
  println(i)
}

fun forEach_label(ints: List<Int>)
{
  var i =2
  ints.forEach {
    //forEach中無(wú)法使用continue和break;
//    if (it == 0) continue //編譯錯(cuò)誤
//    if (it == 2) /*break //編譯錯(cuò)誤 */
    print(it)
  }
   run outer@{
     ints.forEach {
       if (it == 0) return@forEach //相當(dāng)于在forEach函數(shù)中continue,實(shí)際上是從匿名函數(shù)返回
       if (it == 2) return@outer //相當(dāng)于在forEach函數(shù)中使用break,實(shí)際上是跳轉(zhuǎn)到outer之外
     }
   }

  if (i == 3)
  {
    //每個(gè)函數(shù)的名字代表一個(gè)函數(shù)地址，所以函數(shù)自動(dòng)成為標(biāo)簽
    return@forEach_label //等同于return
  }
}

// 一個(gè)參數(shù)
var callback: ((str: String) -> Unit)? = null
callback = { println(it)}
// 判斷并使用
callback?.invoke("hello")

//兩個(gè)參數(shù)
var callback2: ((name: String, age: Int) -> Unit)? = null
callback2 = { hello: String, world: Int -> println("$hello's age is $world") }
callback2?.invoke("Tom", 22)

var callback3 :((num1:Int, num2: Int)->String)? = null
//類(lèi)型可以推斷
callback3 = { num1, num2 ->
  var res:Int = num1 + num2
  res.toString()
}

println(callback3?.invoke(1, 2))