受保护的范围

受保护的作用域允许从当前类的任何子类访问该值。

class FooClass {
  protected val x = "foo"
}
class BarClass extends FooClass {
  val y = x // It is a subclass instance, will compile
}
class ClassB {
  val f = new FooClass
  f.x // <- This will not compile
}