val、var

package com_1030

class Person {
  var name:String="rose"

  def sum(n1:Int,n2:Int):Int={
    n1+n2
  }
}
object Person{
  def main(args: Array[String]): Unit = {
    //创建person对象
    var person=new Person()
    println(person.sum(10,20))//30

    println(person.name)
    person.name="www"
    println(person.name)
    //可以new,内存地址可以变
    person=new Person()

    //声明引用数据类型的常量
    val person2=new Person()
    println(person2.name)
    person2.name="rose456"
    println(person2.name)

    //不可以new,内存地址不能变
    //不可以为引用数据类型的常量重新分配内存
    //×××----------person2=new Person()

  }
}

辅助构造器、主构造器 

package com_1030

class Person1{
  var name:String=_
  var age:Int=_

  //定义辅助构造器
  def this(name:String){

    //辅助构造器必须调用主构造器
    this()
    //给name赋值
    this.name=name
    println("辅助构造器")
  }
def this(age:Int){
  //调用主构造器
  this()
  this.age=age
  println("辅助构造器")
}
  def this(name:String,age:Int){
    this()
    this.name=name
    this.age=age
    println("辅助构造器")
  }
  println("主构造器")

}
object Person1{
  def main(args: Array[String]): Unit = {
    //创建对象
    var p1=new Person1("rose")
    println(p1.name)
    var p2=new Person1(20)
    println(p2.age)
    var p3=new Person1("jack",28)
    println(p3.name+":::"+p3.age)
  }

}

继承 

package com_1030

class Person2 (nameParam:String){
  var name:String=nameParam
  var age:Int=_

//创建辅助构造器
  def this(name:String,age:Int){
    this(name)

    //给age赋值
    this.age=age
    println("父类的辅助构造器")
  }
println("父类的主构造器")
}
//创建子类继承Person
class Emp(nameParam:String,ageParam:Int) extends Person2(nameParam,ageParam){
var empNo:Int=_

  //创建子类的辅助构造器
  def this(name:String,age:Int,empNo:Int){
    //调用主构造
    this(name,age)
    this.empNo=empNo
    println("子类的辅助构造器")
  }
  println("子类的主构造器")
}

object Emp{
  def main(args: Array[String]): Unit = {
    var emp=new Emp("rose",25,1002121)
  }
}