Scala 趣题 4

程序的输出是什么？

trait A {
  val foo: Int
  val bar = 10
  println("In A: foo: " + foo + ", bar: " + bar)
}

class B extends A {
  val foo: Int = 25
  println("In B: foo: " + foo + ", bar: " + bar)}
 
class C extends B {
  override val bar = 99
  println("In C: foo: " + foo + ", bar: " + bar)
}

new C

Explanation

Notice that bar is a val that is overridden in C. The Scala compiler will only initialize vals once, so since bar will be initialized in C it is not initialized before that time and appears as its default value (0, in this case) during the construction of the superclass.