1.定義一個類

// 第一種主構(gòu)造函數(shù)
class Friend constructor(val name:String, val age:Int){}

// 2
class Friend constructor(name:String, age:Int){
  val name = name
  val age = age
}

// constructor關(guān)鍵字可以省略,如果主構(gòu)造函數(shù)有注解或者修飾符就不能省略
class Friend(val name:String, val age:Int){}

// 主構(gòu)造函數(shù)里面是不能有代碼的，但是有一個init代碼塊可以在里面寫構(gòu)造之后的邏輯代碼
class Friend(name:String, age:Int){
  init{
    print("Hello,Friend${name}")
  }
  val name = name
  val age = age
}

// 次構(gòu)造函數(shù)
class Friend{
  constructor(name:String, age:Int){
    this.name = name
    this.age = age
  }
  val name:String
  val age:Int
}

// 主構(gòu)造函數(shù) 加 次構(gòu)造函數(shù)，次構(gòu)造還是要轉(zhuǎn)到主構(gòu)造
class Friend(name:String, age:Int){
  constructor(name:String, age:Int, height:Int):this(name, age){
    this.height = height
  }
  val name:String = name
  val age:Int = age
  val height:Int? = null 
}

2.私有化構(gòu)造方法

class Friend private constructor(){}

3.函數(shù)作為屬性賦值

class numComputer(val num1:Int, val num2:Int, var operator: (int, int)->int){
  fun operation():Int{
    return operator(num1, num2)
  }
}

val nc = numComputer(1,2){x, y -> x+y}
nc.operation()
nc.operator = {x, y-> x*y}
nc.operation()

4.屬性的get() set() 方法

var 是可變屬性，具有g(shù)et() 和set()方法
val是常量， 所以沒有set() 方法

calss Person(age: Int){
  var age = age
    set(value){
      // 給當(dāng)前的這個屬性賦值
      field = value
      isAudlt = if(age>18) true else false
    }
  var isAudlt:Boolean= false
    private set
  var addAge:int = 0
    set(value){
      age += value
    }
}