内部类：定义在类里面的类（内部类可以访问私有成员用它来操作类的私有成员，封闭性更好）
class Student{var age=18def say():Unit={}class Book{val bookName: Any = "Scala程序设计"}}object Test19 {def main(args: Array[String]): Unit = {val s1=new Student()val book1=new s1.Book()println(book1.bookName)}}输出：Scala程序设计class Car2 {private var speed=100val color="red"//class Engin(var maxSpeed:Int){def acc():Unit={speed+=10if (speed>maxSpeed){speed=maxSpeed}println("speed",speed)}def sub():Unit={speed-=10}}override def toString: String = {s"当前的速度是${speed}"}
}
object Test19_1{def main(args: Array[String]): Unit = {val c=new Car2()var engin=new c.Engin(maxSpeed=120)engin.acc()engin.acc()engin.acc()println(c)engin.sub()println(c)}}输出：(speed,110)
(speed,120)
(speed,120)
当前的速度是120
当前的速度是110
)
