scala类与伴生类、单例

类似python元类与apply方法类似python中call方法

class Person(name: String, var age: Int){
  println("Person")
  //private[this] var age = 18 // 字段必须得初始化
  var gender:String=_
  def Age=age  //这个是方法
  def increamen(){age+=1}
  def this(name:String, age:Int, gender:String) {
    this(name, age)  //调用主构造函数
    this.gender = gender
  }
  override def toString() :String = {
    this.age+this.gender+this.name
  }

}

class Student{
  var age: Int = _
  private[this] var gender = "male"
  private var name: String = _

  def getName = this.name

  def setName(value:String){this.name=value}

  def this(age: Int, name: String) {
    this() // 调用主构造函数
    this.age = age
    this.name = name
  }
  override def toString(): String ={
    this.age+this.name
  }
}

// object 类命与class类命相同并且在一个文件中，伴生类，object下的成员都是静态的 ,
若有同名的class,这其作为它的伴生类。在object中一般可以为伴生类做一些初始化等操作

// 使用apply实现单例
object Dog{
  private var age = 0
  var instance:Dog = null
  def Age():Int = {
    age += 1
    age
  }

  def apply(): Dog ={
    println("obeject ApplyTest---apply()---")
    if (instance == null){
      instance = new Dog()
    }
    instance
  }
}

class Dog{
  var age1 = Dog.age // //Dog.age是object Dog的私有字段
  def apply(): Unit ={
    println("class Dog ---apply()---")
  }
}

object hW{
   def main(args:Array[String]): Unit ={
    var dog1 = Dog()
    println(dog1.age1)
    dog1()

    var dog2 = Dog()
    println(dog1.equals(dog2))
}