继承

1、继承的调用顺序：父类构造器 -> 子类构造器

2、scala是单继承

例子：

object Test4_Inherit {
  def main(args: Array[String]): Unit = {
    val student41 = new Student41("wl", 22)
    val student42 = new Student41("wll", 22, "654321")
    student41.printInfo()
    student42.printInfo()
  }
}

class Person4() {
  var name:String = _
  var age:Int = _

  println("1.父类的主构造器调用")

  def this(name:String, age:Int) {
    this()
    println("2.父类的辅助构造器调用")
    this.name = name
    this.age = age

  }
  def printInfo(): Unit = {
    println(s"Person: $name $age")
  }
}

class Student41(name:String, age:Int) extends Person4() {
  var stuNo:String = _
  println("3.子类的主构造器调用")

  def this(name: String, age: Int, stuNo: String){
    this(name, age)
    println("4.子类的辅助构造器调用")
    this.stuNo = stuNo
  }

  //重写父类方法
  override def printInfo(): Unit = {
    println(s"Student41: $name $age $stuNo")
  }
}